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The Dark(S)Eye'd: GEODEs or a Singularity of The Darkside.
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SEPTEMBER 10, 2019
Are black holes made of dark energy?
[Image: areblackhole.jpg]Objects like Powehi, the recently imaged supermassive compact object at the center of galaxy M87, might actually be GEODEs. The Powehi GEODE, shown to scale, would be approximately 2/3 the radius of the dark region imaged by the Event Horizon Telescope. This is nearly the same size expected for a black hole. The region containing Dark Energy (green) is slightly larger than a black hole of the same mass. The properties of any crust (purple), if present, depend on the particular GEODE model. Credit: EHT collaboration; NASA/CXC/Villanova University
Two University of Hawaii at Manoa researchers have identified and corrected a subtle error that was made when applying Einstein's equations to model the growth of the universe.

Physicists usually assume that a cosmologically large system, such as the universe, is insensitive to details of the small systems contained within it. Kevin Croker, a postdoctoral research fellow in the Department of Physics and Astronomy, and Joel Weiner, a faculty member in the Department of Mathematics, have shown that this assumption can fail for the compact objects that remain after the collapse and explosion of very large stars.
"For 80 years, we've generally operated under the assumption that the universe, in broad strokes, was not affected by the particular details of any small region," said Croker. "It is now clear that general relativity can observably connect collapsed stars—regions the size of Honolulu—to the behavior of the universe as a whole, over a thousand billion billion times larger."
Croker and Weiner demonstrated that the growth rate of the universe can become sensitive to the averaged contribution of such compact objects. Likewise, the objects themselves can become linked to the growth of the universe, gaining or losing energy depending on the objects' compositions. This result is significant since it reveals unexpected connections between cosmological and compact object physics, which in turn leads to many new observational predictions.
One consequence of this study is that the growth rate of the universe provides information about what happens to stars at the end of their lives. Astronomers typically assume that large stars form black holes when they die, but this is not the only possible outcome. In 1966, Erast Gliner, a young physicist at the Ioffe Physico-Technical Institute in Leningrad, proposed an alternative hypothesis that very large stars should collapse into what could now be called Generic Objects of Dark Energy (GEODEs). These appear to be black holes when viewed from the outside but, unlike black holes, they contain Dark Energy instead of a singularity.
In 1998, two independent teams of astronomers discovered that the expansion of the Universe is accelerating, consistent with the presence of a uniform contribution of Dark Energy. It was not recognized, however, that GEODEs could contribute in this way. With the corrected formalism, Croker and Weiner showed that if a fraction of the oldest stars collapsed into GEODEs, instead of black holes, their averaged contribution today would naturally produce the required uniform Dark Energy.
The results of this study also apply to the colliding double star systems observable through gravitational waves by the LIGO-Virgo collaboration. In 2016, LIGO announced the first observation of what appeared to be a colliding double black hole system. Such systems were expected to exist, but the pair of objects was unexpectedly heavy—roughly 5 times larger than the black hole masses predicted in computer simulations. Using the corrected formalism, Croker and Weiner considered whether LIGO-Virgo is observing double GEODE collisions, instead of double black hole collisions. They found that GEODEs grow together with the universe during the time leading up to such collisions. When the collisions occur, the resulting GEODE masses become 4 to 8 times larger, in rough agreement with the LIGO-Virgo observations.
Croker and Weiner were careful to separate their theoretical result from observational support of a GEODE scenario, emphasizing that "black holes certainly aren't dead. What we have shown is that if GEODEs do exist, then they can easily give rise to observed phenomena that presently lack convincing explanations. We anticipate numerous other observational consequences of a GEODE scenario, including many ways to exclude it. We've barely begun to scratch the surface."
The study, Implications of Symmetry and Pressure in Friedmann Cosmology: I. Formalism, is published in the August 28, 2019 issue of The Astrophysical Journal and is available online.




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Where in the universe can you find a black hole nursery?



[b]More information:[/b] K. S. Croker et al. Implications of Symmetry and Pressure in Friedmann Cosmology. I. Formalism, The Astrophysical Journal (2019). DOI: 10.3847/1538-4357/ab32da
[b]Journal information:[/b] Astrophysical Journal [/url]

Provided by 
University of Hawaii at Manoa 


Dark(S) Eye'd  Arrow

SEPTEMBER 13, 2019
Engineers develop 'blackest black' material to date
[Image: 2-mitengineers.jpg]MIT engineers have cooked up a material made of carbon nanotubes that is 10 times blacker than anything that has previously been reported. Credit: R. Capanna, A. Berlato, and A. Pinato
With apologies to "Spinal Tap," it appears that black can, indeed, get more black.

MIT engineers report today that they have cooked up a material that is 10 times blacker than anything that has previously been reported. The material is made from vertically aligned carbon nanotubes, or CNTs—microscopic filaments of carbon, like a fuzzy forest of tiny trees, that the team grew on a surface of chlorine-etched aluminum foil. The foil captures more than 99.96 percent of any incoming light, making it the blackest material on record.
The researchers have published their findings today in the journal ACS-Applied Materials and Interfaces. They are also showcasing the cloak-like material as part of a new exhibit today at the New York Stock Exchange, titled "The Redemption of Vanity."
The artwork, a collaboration between Brian Wardle, professor of aeronautics and astronautics at MIT, and his group, and MIT artist-in-residence Diemut Strebe, features a 16.78-carat natural yellow diamond, estimated to be worth $2 million, which the team coated with the new, ultrablack CNT material. The effect is arresting: The gem, normally brilliantly faceted, appears as a flat, black void.
Wardle says the CNT material, aside from making an artistic statement, may also be of practical use, for instance in optical blinders that reduce unwanted glare, to help space telescopes spot orbiting exoplanets.
"There are optical and space science applications for very black materials, and of course, artists have been interested in black, going back well before the Renaissance," Wardle says. "Our material is 10 times blacker than anything that's ever been reported, but I think the blackest black is a constantly moving target. Someone will find a blacker material, and eventually we'll understand all the underlying mechanisms, and will be able to properly engineer the ultimate black."
Wardle's co-author on the paper is former MIT postdoc Kehang Cui, now a professor at Shanghai Jiao Tong University.
[b]Into the void[/b]
Wardle and Cui didn't intend to engineer an ultrablack material. Instead, they were experimenting with ways to grow carbon nanotubes on electrically conducting materials such as aluminum, to boost their electrical and thermal properties.

But in attempting to grow CNTs on aluminum, Cui ran up against a barrier, literally: an ever-present layer of oxide that coats aluminum when it is exposed to air. This oxide layer acts as an insulator, blocking rather than conducting electricity and heat. As he cast about for ways to remove aluminum's oxide layer, Cui found a solution in salt, or sodium chloride.
At the time, Wardle's group was using salt and other pantry products, such as baking soda and detergent, to grow carbon nanotubes. In their tests with salt, Cui noticed that chloride ions were eating away at aluminum's surface and dissolving its oxide layer.
"This etching process is common for many metals," Cui says. "For instance, ships suffer from corrosion of chlorine-based ocean water. Now we're using this process to our advantage."
Cui found that if he soaked aluminum foil in saltwater, he could remove the oxide layer. He then transferred the foil to an oxygen-free environment to prevent reoxidation, and finally, placed the etched aluminum in an oven, where the group carried out techniques to grow carbon nanotubes via a process called chemical vapor deposition.
By removing the oxide layer, the researchers were able to grow carbon nanotubes on aluminum, at much lower temperatures than they otherwise would, by about 100 degrees Celsius. They also saw that the combination of CNTs on aluminum significantly enhanced the material's thermal and electrical properties—a finding that they expected.
What surprised them was the material's color.
"I remember noticing how black it was before growing carbon nanotubes on it, and then after growth, it looked even darker," Cui recalls. "So I thought I should measure the optical reflectance of the sample.
"Our group does not usually focus on optical properties of materials, but this work was going on at the same time as our art-science collaborations with Diemut, so art influenced science in this case," says Wardle.
Wardle and Cui, who have applied for a patent on the technology, are making the new CNT process freely available to any artist to use for a noncommercial art project.
[b]"Built to take abuse"[/b]
Cui measured the amount of light reflected by the material, not just from directly overhead, but also from every other possible angle. The results showed that the material absorbed greater than 99.995 percent of incoming light, from every angle. In essence, if the material contained bumps or ridges, or features of any kind, no matter what angle it was viewed from, these features would be invisible, obscured in a void of black.
The researchers aren't entirely sure of the mechanism contributing to the material's opacity, but they suspect that it may have something to do with the combination of etched aluminum, which is somewhat blackened, with the carbon nanotubes. Scientists believe that forests of carbon nanotubes can trap and convert most incoming light to heat, reflecting very little of it back out as light, thereby giving CNTs a particularly black shade.
"CNT forests of different varieties are known to be extremely black, but there is a lack of mechanistic understanding as to why this material is the blackest. That needs further study," Wardle says.




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Pantry ingredients can help grow carbon nanotubes



[b]More information:[/b] Kehang Cui et al. Breakdown of Native Oxide Enables Multifunctional, Free-Form Carbon Nanotube–Metal Hierarchical Architectures, ACS Applied Materials & Interfaces (2019). DOI: 10.1021/acsami.9b08290
[b]Journal information:[/b] ACS Applied Materials and Interfaces 

Provided by Massachusetts Institute of Technology 



https://phys.org/news/2019-09-blackest-b...-date.html

What if The Input was A Black Hole?
Would The output be a Black Whole?

GEODEs  Sheep Singularity.

Refusing to shed light on THE matter...Accepts that THE light doesn't matter


SEPTEMBER 6, 2019
Black hole movies coming soon, says leading astronomer
[Image: 5caded214d11e.jpg]Credit: NSF
By the time an international group of scientists stunned the world with the first ever image of a black hole, they were already planning a sequel: a movie showing how massive clouds of gas are forever sucked into the void.

The Event Horizon Telescope Collaboration has already recorded the necessary observations and is processing the mountains of data to produce the first video, which will likely be a little jerky, in 2020.
"What I predict is that by the end of the next decade we will be making high quality real-time movies of black holes that reveal not just how they look, but how they act on the cosmic stage," Shep Doeleman, the project's director, told AFP in an interview.
The entire team, comprising 347 scientists from around the world, were honored Thursday with the Breakthrough Prize in Fundamental Physics, winning $3 million for the so-called "Oscar of science" for the image they released on April 10.
"I've been working on this for 20 years. So my wife was finally convinced that what I was doing was worth it a little bit," joked the 52-year-old father of two, who is an astronomer at the Harvard-Smithsonian Center for Astrophysics.
Astronomers could previously detect the light that is being swallowed by black holes, but "we just didn't have the sharpness in our images to see what shape the light had."
That obstacle was ultimately overcome when the team linked multiple radio telescopes together, thus simulating an Earth-sized giant telescope capable of observing at an unprecedented resolution objects that appear microscopic in the night sky.
[b]Galactic explorers[/b]
Toward the end of the 2000s, the hard work began to pay off. The team obtained approval to use three telescopes to establish a proof of concept, and in 2008 published the first measurements of a black hole.
By April 2017, they had assembled eight radio telescopes in Chile, Spain, Mexico, the US, and the South Pole.
The giant instruments observe high frequency radio waves, allowing astronomers to see through the gas and dust of the galaxy, all the way through to the boundaries of black holes.
In addition to its observations of the black hole in the Messier 87 (M87) galaxy, the team also looked at the one at the center of our own Milky Way: Sagittarius-A*.
They took readings in 2018, and plan to repeat them next year.
Our own black hole is far more turbulent and therefore difficult to observe.
"Orbits of matter around M87 take about a month to circulate. Whereas orbits around Sagittarius-A* can take only half an hour, during one night of observing Sagittarius-A* can change before your eyes," explained Doeleman.
"It could be that maybe we will make the first crude movie" by 2020, he added. Ideally, scientists would need more telescopes, both on Earth and in orbit, to improve the resolution yet further.
But the manner in which the first image of M87 has captured people's imagination has left Doeleman optimistic about the prospect of future funding, both from governments and possibly private donors.
"The EHT has delivered more value than any other scientific project that I can think of in history," he said.
"We do see ourselves as explorers, we've taken a journey in our minds. And we are instruments at the edge of a black hole. And now we're coming back to report what we found."




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Team behind world's first black hole image wins 'Oscar of science





[Image: latest?cb=20140122145113]cb=20140122145113

RECALL: 


Quote:SEPTEMBER 10, 2019
Are black holes made of dark energy?
[Image: areblackhole.jpg]Objects like Powehi, the recently imaged supermassive compact object at the center of galaxy M87, might actually be GEODEs. The Powehi GEODE, shown to scale, would be approximately 2/3 the radius of the dark region imaged by the Event Horizon Telescope. This is nearly the same size expected for a black hole. The region containing Dark Energy (green) is slightly larger than a black hole of the same mass. The properties of any crust (purple), if present, depend on the particular GEODE model. Credit: EHT collaboration; NASA/CXC/Villanova University
Two University of Hawaii at Manoa researchers have identified and corrected a subtle error that was made when applying Einstein's equations to model the growth of the universe. Arrow



Arrow MAJOR RE-Writes Itself.



SEPTEMBER 12, 2019
Study finds the universe might be 2 billion years younger
by Seth Borenstein
[Image: 3-studyfindsth.jpg]This image made available by the European Space agency shows galaxies in the Hubble Ultra Deep Field 2012, an improved version of the Hubble Ultra Deep Field image. A study from the Max Planck Institute in Germany published Thursday, Sept. 12, 2019, in the journal Science uses a new technique to come up with a rate that the universe is expanding that is nearly 18% higher than the number scientists had been using since the year 2000. (NASA, ESA, R. Ellis (Caltech), HUDF 2012 Team via AP)
The universe is looking younger every day, it seems.

New calculations suggest the universe could be a couple billion years younger than scientists now estimate, and even younger than suggested by two other calculations published this year that trimmed hundreds of millions of years from the age of the cosmos.
The huge swings in scientists' estimates—even this new calculation could be off by billions of years—reflect different approaches to the tricky problem of figuring the universe's real age.
"We have large uncertainty for how the stars are moving in the galaxy," said Inh Jee, of the Max Plank Institute in Germany, lead author of the study in Thursday's journal Science .
Scientists estimate the age of the universe by using the movement of stars to measure how fast it is expanding. If the universe is expanding faster, that means it got to its current size more quickly, and therefore must be relatively younger.
The expansion rate, called the Hubble constant , is one of the most important numbers in cosmology. A larger Hubble Constant makes for a faster moving—and younger—universe.
The generally accepted age of the universe is 13.7 billion years, based on a Hubble Constant of 70.
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An animation of B1608+656 variability in radio observations. The top panel shows four lensed images of a background quasar, and the bottom panel shows the light curves of the four images. Credit: S.H. Suyu, C.D. Fassnacht, NRAO/AUI/NSF
Jee's team came up with a Hubble Constant of 82.4, which would put the age of the universe at around 11.4 billion years.
Jee used a concept called gravitational lensing—where gravity warps light and makes far away objects look closer. They rely on a special type of that effect called time delay lensing, using the changing brightness of distant objects to gather information for their calculations.
But Jee's approach is only one of a few new ones that have led to different numbers in recent years, reopening a simmering astronomical debate of the 1990s that had been seemingly settled.
In 2013, a team of European scientists looked at leftover radiation from the Big Bang and pronounced the expansion rate a slower 67, while earlier this year Nobel Prize winning astrophysicist Adam Riess of the Space Telescope Science Institute used NASA's super telescope and came up with a number of 74. And another team earlier this year came up with 73.3.
Jee and outside experts had big caveats for her number. She used only two gravitational lenses, which were all that were available, and so her margin of error is so large that it's possible the universe could be older than calculated, not dramatically younger.
Harvard astronomer Avi Loeb, who wasn't part of the study, said it an interesting and unique way to calculate the universe's expansion rate, but the large error margins limits its effectiveness until more information can be gathered.
"It is difficult to be certain of your conclusions if you use a ruler that you don't fully understand," Loeb said in an email.




[b]Explore further

Scientists debate the seriousness of problems with the value of the Hubble Constant
[/b]


[b][b]More information:[/b] I. Jee el al., "A measurement of the Hubble constant from angular diameter distances to two gravitational lenses," Science (2019). science.sciencemag.org/cgi/doi … 1126/science.aat7371

"An expanding controversy," Science (2019). science.sciencemag.org/cgi/doi … 1126/science.aay1331
[b]Journal information:[/b] Science

 [/b]

https://phys.org/news/2019-09-universe-b...unger.html

I'm Not Hawking Radiation...nope.
Eye'm selling Snake-Oil Y'all for free...


SEPTEMBER 11, 2019
Black hole at the center of our galaxy appears to be getting hungrier
[Image: blackholeatt.jpg]Rendering of a star called S0-2 orbiting the supermassive black hole at the center of the Milky Way. It did not fall in, but its close approach could be one reason for the black hole's growing appetite. Credit: Artist's rendering by Nicolle Fuller/National Science Foundation
The enormous black hole at the center of our galaxy is having an unusually large meal of interstellar gas and dust, and researchers don't yet understand why.

"We have never seen anything like this in the 24 years we have studied the supermassive black hole," said Andrea Ghez, UCLA professor of physics and astronomy and a co-senior author of the research. "It's usually a pretty quiet, wimpy black hole on a diet. We don't know what is driving this big feast."
A paper about the study, led by the UCLA Galactic Center Group, which Ghez heads, is published today in Astrophysical Journal Letters.
The researchers analyzed more than 13,000 observations of the black hole from 133 nights since 2003. The images were gathered by the W.M. Keck Observatory in Hawaii and the European Southern Observatory's Very Large Telescope in Chile. The team found that on May 13, the area just outside the black hole's "point of no return" (so called because once matter enters, it can never escape) was twice as bright as the next-brightest observation.
They also observed large changes on two other nights this year; all three of those changes were "unprecedented," Ghez said.
The brightness the scientists observed is caused by radiation from gas and dust falling into the black hole; the findings prompted them to ask whether this was an extraordinary singular event or a precursor to significantly increased activity.
"The big question is whether the black hole is entering a new phase—for example if the spigot has been turned up and the rate of gas falling down the black hole 'drain' has increased for an extended period—or whether we have just seen the fireworks from a few unusual blobs of gas falling in," said Mark Morris, UCLA professor of physics and astronomy and the paper's co-senior author.

The team has continued to observe the area and will try to settle that question based on what they see from new images.
"We want to know how black holes grow and affect the evolution of galaxies and the universe," said Ghez, UCLA's Lauren B. Leichtman and Arthur E. Levine Professor of Astrophysics. "We want to know why the supermassive hole gets brighter and how it gets brighter."

The new findings are based on observations of the black hole—which is called Sagittarius A*, or Sgr A*—during four nights in April and May at the Keck Observatory. The brightness surrounding the black hole always varies somewhat, but the scientists were stunned by the extreme variations in brightness during that timeframe, including their observations on May 13.
"The first image I saw that night, the black hole was so bright I initially mistook it for the star S0-2, because I had never seen Sagittarius A* that bright," said UCLA research scientist Tuan Do, the study's lead author. "But it quickly became clear the source had to be the black hole, which was really exciting."
One hypothesis about the increased activity is that when a star called S0-2 made its closest approach to the black hole during the summer 2018, it launched a large quantity of gas that reached the black hole this year.
Another possibility involves a bizarre object known as G2, which is most likely a pair of binary stars, which made its closest approach to the black hole in 2014. It's possible the black hole could have stripped off the outer layer of G2, Ghez said, which could help explain the increased brightness just outside the black hole.
Morris said another possibility is that the brightening corresponds to the demise of large asteroids that have been drawn in to the black hole.

[b]No danger to Earth[/b]
The black hole is some 26,000 light-years away and poses no danger to our planet. Do said the radiation would have to be 10 billion times as bright as what the astronomers detected to affect life on Earth.
Astrophysical Journal Letters also published a second article by the researchers, describing speckle holography, the technique that enabled them to extract and use very faint information from 24 years of data they recorded from near the black hole.
Ghez's research team reported July 25 in the journal Science the most comprehensive test of Einstein's iconic general theory of relativity near the black hole. Their conclusion that Einstein's theory passed the test and is correct, at least for now, was based on their study of S0-2 as it made a complete orbit around the black hole.
Ghez's team studies more than 3,000 stars that orbit the supermassive black hole. Since 2004, the scientists have used a powerful technology that Ghez helped pioneer, called adaptive optics, which corrects the distorting effects of the Earth's atmosphere in real time. But speckle holography enabled the researchers to improve the data from the decade before adaptive optics came into play. Reanalyzing data from those years helped the team conclude that they had not seen that level of brightness near the black hole in 24 years.
"It was like doing LASIK surgery on our early images," Ghez said. "We collected the data to answer one question and serendipitously unveiled other exciting scientific discoveries that we didn't anticipate."




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Einstein's general relativity theory is questioned but still stands for now



[b]More information:[/b] Tuan Do et al. Unprecedented Near-infrared Brightness and Variability of Sgr A*, The Astrophysical Journal (2019). DOI: 10.3847/2041-8213/ab38c3

Zhuo Chen et al. Consistency of the Infrared Variability of SGR A* over 22 yr, The Astrophysical Journal (2019). DOI: 10.3847/2041-8213/ab3c68
[b]Journal information:[/b] Astrophysical Journal Letters  Astrophysical Journal 

Provided by University of California, Los Angeles

https://phys.org/news/2019-09-black-hole...grier.html

Arrow

SEPTEMBER 11, 2019
Scientists detect the ringing of a newborn black hole for the first time
[Image: 4-blackhole.jpg]Credit: CC0 Public Domain
If Albert Einstein's theory of general relativity holds true, then a black hole, born from the cosmically quaking collisions of two massive black holes, should itself "ring" in the aftermath, producing gravitational waves much like a struck bell reverbates sound waves. Einstein predicted that the particular pitch and decay of these gravitational waves should be a direct signature of the newly formed black hole's mass and spin.

Now, physicists from MIT and elsewhere have "heard" the ringing of an infant black hole for the first time, and found that the pattern of this ringing does, in fact, predict the black hole's mass and spin—more evidence that Einstein was right all along.
The findings, published today in Physical Review Letters, also favor the idea that black holes lack any sort of "hair"—a metaphor referring to the idea that black holes, according to Einstein's theory, should exhibit just three observable properties: mass, spin, and electric charge. All other characteristics, which the physicist John Wheeler termed "hair," should be swallowed up by the black hole itself, and would therefore be unobservable.
The team's findings today support the idea that black holes are, in fact, hairless. The researchers were able to identify the pattern of a black hole's ringing, and, using Einstein's equations, calculated the mass and spin that the black hole should have, given its ringing pattern. These calculations matched measurements of the black hole's mass and spin made previously by others.
If the team's calculations deviated significantly from the measurements, it would have suggested that the black hole's ringing encodes properties other than mass, spin, and electric charge—tantalizing evidence of physics beyond what Einstein's theory can explain. But as it turns out, the black hole's ringing pattern is a direct signature of its mass and spin, giving support to the notion that black holes are bald-faced giants, lacking any extraneous, hair-like properties.
"We all expect general relativity to be correct, but this is the first time we have confirmed it in this way," says the study's lead author, Maximiliano Isi, a NASA Einstein Fellow in MIT's Kavli Institute for Astrophysics and Space Research. "This is the first experimental measurement that succeeds in directly testing the no-hair theorem. It doesn't mean black holes couldn't have hair. It means the picture of black holes with no hair lives for one more day."
[b]A chirp, decoded[/b]
On Sept. 9, 2015, scientists made the first-ever detection of gravitational waves—infinitesimal ripples in space-time, emanating from distant, violent cosmic phenomena. The detection, named GW150914, was made by LIGO, the Laser Interferometer Gravitational-wave Observatory. Once scientists cleared away the noise and zoomed in on the signal, they observed a waveform that quickly crescendoed before fading away. When they translated the signal into sound, they heard something resembling a "chirp."

Scientists determined that the gravitational waves were set off by the rapid inspiraling of two massive black holes. The peak of the signal—the loudest part of the chirp—linked to the very moment when the black holes collided, merging into a single, new black hole. While this infant black hole likely gave off gravitational waves of its own, its signature ringing, physicists assumed, would be too faint to decipher amid the clamor of the initial collision.

This simulation shows how a black hole merger would appear to our eyes if we could somehow travel in a spaceship for a closer look. It was created by solving equations from Albert Einstein's general theory of relativity using LIGO data from the event called GW150914. Credit: SXS, the Simulating eXtreme Spacetimes (SXS) project
Isi and his colleagues, however, found a way to extract the black hole's reverberation from the moments immediately after the signal's peak. In previous work led by Isi's co-author, Matthew Giesler, the team showed through simulations that such a signal, and particularly the portion right after the peak, contains "overtones"—a family of loud, short-lived tones. When they reanalyzed the signal, taking overtones into account, the researchers discovered that they could successfully isolate a ringing pattern that was specific to a newly formed black hole.
In the team's new paper, the researchers applied this technique to actual data from the GW150914 detection, concentrating on the last few milliseconds of the signal, immediately following the chirp's peak. Taking into account the signal's overtones, they were able to discern a ringing coming from the new, infant black hole. Specifically, they identified two distinct tones, each with a pitch and decay rate that they were able to measure.
"We detect an overall gravitational wave signal that's made up of multiple frequencies, which fade away at different rates, like the different pitches that make up a sound," Isi says. "Each frequency or tone corresponds to a vibrational frequency of the new black hole."
[b]Listening beyond Einstein[/b]
Einstein's theory of general relativity predicts that the pitch and decay of a black hole's gravitational waves should be a direct product of its mass and spin. That is, a black hole of a given mass and spin can only produce tones of a certain pitch and decay. As a test of Einstein's theory, the team used the equations of general relativity to calculate the newly formed black hole's mass and spin, given the pitch and decay of the two tones they detected.
They found their calculations matched with measurements of the black hole's mass and spin previously made by others. Isi says the results demonstrate that researchers can, in fact, use the very loudest, most detectable parts of a gravitational wave signal to discern a new black hole's ringing, where before, scientists assumed that this ringing could only be detected within the much fainter end of the gravitational wave signal, and only with much more sensitive instruments than what currently exist.
"This is exciting for the community because it shows these kinds of studies are possible now, not in 20 years," Isi says.
As LIGO improves its resolution, and more sensitive instruments come online in the future, researchers will be able to use the group's methods to "hear" the ringing of other newly born black holes. And if they happen to pick up tones that don't quite match up with Einstein's predictions, that could be an even more exciting prospect.
"In the future, we'll have better detectors on Earth and in space, and will be able to see not just two, but tens of modes, and pin down their properties precisely," Isi says. "If these are not black holes as Einstein predicts, if they are more exotic objects like wormholes or boson stars, they may not ring in the same way, and we'll have a chance of seeing them."




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Shedding light on black holes



[b]More information:[/b] Testing the no-hair theorem with GW150914, arXiv:1905.00869 [gr-qc] arxiv.org/abs/1905.00869
[b]Journal information:[/b] Physical Review Letters 

Provided by Massachusetts Institute of Technology

https://phys.org/news/2019-09-scientists...-hole.html







SEPTEMBER 10, 2019
Mid-mass black hole hurls star across the Milky Way
[Image: midmassblack.jpg]Credit: A. Irrgang, Fau
An international team of astronomers has pinpointed the origin of a runaway high-velocity star named PG 1610+062 and determined that it was likely ejected from its birth cluster with the help of a mid-mass black hole (MMBH).

The findings are published in the journal Astronomy & Astrophysics.
In order to put tight constraints on PG 1610+062's projected rotational velocity, its radial velocity, as well as measure its chemical composition accurately, the team needed spectral data of the star, but its distance and position in the sky made W. M. Keck Observatory's Echellette Spectrograph and Imager (ESI) the only tool for the job.
"In the northern hemisphere, only the combination of Keck Observatory and ESI gave us what we needed. The collecting area of Keck allowed us to gather enough photons for our object and ESI has exactly the right resolution, which is high enough to resolve all the spectral features," says co-author Thomas Kupfer, a Kavli Institute for Theoretical Physics Postdoctoral Scholar at the University of California, Santa Barbara.
While formerly considered an old star with half a solar mass, typical for the galactic halo, the Keck Observatory data revealed that PG1610+062 is actually a surprisingly young star that's ten times more massive, ejected from the Galactic disk almost at the escape velocity from the Milky Way.
Some even faster stars, called hyper-velocity stars (HVSs), do exist—the first three were discovered in 2005. Among them is the unique star US 708, which was found from observations using the Low Resolution Imaging Spectrometer (LRIS) on the Keck I telescope; it was going so fast it escaped the Milky Way's gravitational pull. To achieve such velocities requires an extremely dramatic slingshot event.

[Image: midmassblack.gif]
Young, massive stars like PG 1610+062 in the Milky Way’s galactic halo live far from our galaxy’s star-forming regions. Astronomers are trying to understand how these ‘runaway stars’ were forced to leave their birth place. New observations of PG 1610+062 suggest that a mid-sized black hole in the Milky Way may be responsible for evicting the star from its home cluster. Credit: A. Irrgang, Fau
Simulations carried out in 1988 suggested that a giant, 4 million solar mass black hole (SMBH) could do the trick. By disrupting a binary star system, i.e. swallowing one star and leaving its stellar partner with all the energy in the system, ejecting it far beyond the escape velocity of the Milky Way. Lacking other plausible explanations for the formation of HVSs, this scenario was readily accepted as the standard ejection mechanism, in particular after observational evidence for the existence of such a SMBH at the Galactic Center became overwhelming in the early 2000s.

By using the European Space Agency's Gaia spacecraft's unprecedented astrometric precision measurements, PG1610+062 has been traced back to nowhere near the Galactic Center, but to the Sagittarius spiral arm of our galaxy, therefore ruling out the idea that the Galactic Center SMBH slingshot the star.
Even more interesting is the derived extreme acceleration of PG1610+062, which excludes most likely all alternative scenarios except the interaction with a MMBH. Such objects have been predicted to exist in young stellar clusters in the spiral arms of the Milky Way, but none has been detected yet.
"Now, PG1610+062 may provide evidence that MMBHs could indeed exist in our galaxy. The race is on to actually find them," says lead author Andreas Irrgang of the Friedrich-Alexander University of Erlangen-Nuremberg in Germany.
There is plenty more to learn about this star and its place of origin. As the Gaia mission proceeds, precision will improve and the place of origin will be narrowed down further, possibly allowing astronomers to search for the parent star cluster and ultimately for the black hole.
The team, which includes Felix Fürst of the European Space Astronomy Centre in Spain, Stephan Geier of the Institute of Physics and Astronomy at the University of Potsdam in Germany, and Ulrich Heber of the Friedrich-Alexander University of Erlangen-Nuremberg, is currently searching for additional candidates similar to PG1610+062 using Gaia and other large survey telescopes. The brighter, closer ones might be suitable for tracing back to cores of star clusters, which might provide evidence of intermediate mass black holes in their centers.




Explore further
Researchers confirm massive hyper-runaway star ejected from the Milky Way Disk



[b]More information:[/b] A. Irrgang et al. PG 1610+062: a runaway B star challenging classical ejection mechanisms, Astronomy & Astrophysics (2019). DOI: 10.1051/0004-6361/201935429
[b]Journal information:[/b] Astronomy & Astrophysics 

Provided by W. M. Keck Observatory

https://phys.org/news/2019-09-mid-mass-b...-star.html

GEODEs Sheep  Singularity

SEPTEMBER 12, 2019
Unexpected periodic flares may shed light on black hole accretion
[Image: unexpectedpe.gif]Black hole at the center of a distant galaxy periodically flares up. Credit: European Space Agency
ESA's X-ray space telescope XMM-Newton has detected never-before-seen periodic flares of X-ray radiation coming from a distant galaxy that could help explain some enigmatic behaviours of active black holes.

XMM-Newton, the most powerful X-ray observatory, discovered some mysterious flashes from the active black hole at the core of the galaxy GSN 069, about 250 million light years away. On 24 December 2018, the source was seen to suddenly increase its brightness by up to a factor 100, then dimmed back to its normal levels within one hour and lit up again nine hours later.
"It was completely unexpected," says Giovanni Miniutti, of the Centro de Astrobiología in Madrid, Spain, lead author of a new paper published in the journal Nature today.
"Giant black holes regularly flicker like a candle but the rapid, repeating changes seen in GSN 069 from December onwards are something completely new."
Further observations, performed with XMM-Newton as well as NASA's Chandra X-ray observatory in the following couple of months, confirmed that the distant black hole was still keeping the tempo, emitting nearly periodic bursts of X-rays every nine hours. The researchers are calling the new phenomenon 'quasi-periodic eruptions," or QPEs.
"The X-ray emission comes from material that is being accreted into the black hole and heats up in the process," explains Giovanni.
"There are various mechanisms in the accretion disc that could give rise to this type of quasi-periodic signal, potentially linked to instabilities in the accretion flow close to the central black hole.
"Alternatively, the eruptions could be due to the interaction of the disc material with a second body—another black hole or perhaps the remnant of a star previously disrupted by the black hole."

[Image: 1-unexpectedpe.gif]
Optical and X-ray view. Credit: European Space Agency
Although never before observed, Giovanni and colleagues think periodic flares like these might actually be quite common in the Universe.
It is possible that the phenomenon had not been identified before because most black holes at the cores of distant galaxies, with masses millions to billions of times the mass of our Sun, are much larger than the one in GSN 069, which is only about 400 000 times more massive than our Sun.
The bigger and more massive the black hole, the slower the fluctuations in brightness it can display, so a typical supermassive black hole would erupt not every nine hours, but every few months or years. This would make detection unlikely as observations rarely span such long periods of time.

And there is more. Quasi-periodic eruptions like those found in GSN 069 could provide a natural framework to interpret some puzzling patterns observed in a significant fraction of active black holes, whose brightness seems to vary too fast to be easily explained by current theoretical models.
"We know of many massive black holes whose brightness rises or decays by very large factors within days or months, while we would expect them to vary at a much slower pace," says Giovanni.
"But if some of this variability corresponds to the rise or decay phases of eruptions similar to those discovered in GSN 069, then the fast variability of these systems, which appears currently unfeasible, could naturally be accounted for. New data and further studies will tell if this analogy really holds."
The quasi-periodic eruptions spotted in GSN 069 could also explain another intriguing property observed in the X-ray emission from nearly all bright, accreting supermassive black holes: the so-called 'soft excess."
It consists in enhanced emission at low X-ray energies, and there is still no consensus on what causes it, with one leading theory invoking a cloud of electrons heated up near the accretion disc.

[Image: unexpectedpe.jpg]
Quasi-periodic eruptions in GSN 069. Credit: European Space Agency
Like similar black holes, GSN 069 exhibits such a soft X-ray excess during bursts, but not between eruptions.
"We may be witnessing the formation of the soft excess in real time, which could shed light on its physical origin," says co-author Richard Saxton from the XMM-Newton operation team at ESA's astronomy centre in Spain.
"How the cloud of electrons is created is currently unclear, but we are trying to identify the mechanism by studying the changes in the X-ray spectrum of GSN 069 during the eruptions."
The team is already trying to pinpoint the defining properties of GSN 069 at the time when the periodic eruptions were first detected to look for more cases to study.
"One of our immediate goals is to search for X-ray quasi-periodic eruptions in other galaxies, to further understand the physical origin of this new phenomenon," adds co-author Margherita Giustini of Madrid's Centro de Astrobiología.
"GSN 069 is an extremely fascinating source, with the potential to become a reference in the field of black hole accretion," says Norbert Schartel, ESA's XMM-Newton project scientist.
The discovery would not have been possible without XMM-Newton's capabilities.
"These bursts happen in the low energy part of the X-ray band, where XMM-Newton is unbeatable. We will certainly need to use the observatory again if we want to find more of these kinds of events in the future," concludes Norbert.
"Nine-hour X-ray quasi-periodic eruptions from a low-mass black hole galactic nucleus," by G. Miniutti et al., is published in Nature.




Explore further
How black holes shape galaxies



[b]More information:[/b] G. Miniutti et al. Nine-hour X-ray quasi-periodic eruptions from a low-mass black hole galactic nucleus, Nature (2019). DOI: 10.1038/s41586-019-1556-x
[b]Journal information:[/b] Nature 

Provided by [url=https://phys.org/partners/european-space-agency/]European Space Agency

https://phys.org/news/2019-09-unexpected...-hole.html
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With a forked tongue the snake singsss...
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#2
Our Galaxy's Black Hole Recently Flared Crazily Bright, And We Still Don't Know Why
[Image: sgr-a-bright_1024.gif]
MICHELLE STARR
14 SEP 2019

The supermassive black hole at the heart of the Milky Way, Sagittarius A*, is usually relatively quiet. It's not an active nucleus, spewing light and heat into the space around it; most of the time, the black hole's activity is low key, with minimal fluctuations in its brightness.
Most of the time. Recently, astronomers caught it going absolutely bananas, suddenly growing 75 times brighter before subsiding back to normal levels. That's the brightest we've ever seen Sgr A* in near-infrared wavelengths.
"I was pretty surprised at first and then very excited," astronomer Tuan Do of the University of California Los Angeles (UCLA) told ScienceAlert.
"The black hole was so bright I at first mistook it for the star S0-2, because I had never seen Sgr A* that bright. Over the next few frames, though, it was clear the source was variable and had to be the black hole. I knew almost right away there was probably something interesting going on with the black hole."
But what? That's what astronomers are on a mission to find out. We first reported on this story in mid August, and the results have now been published in[i] The Astrophysical Journal Letters. [/i]As of now, we still don't know what caused the super bright flare.
"We have never seen anything like this in the 24 years we have studied the supermassive black hole," said Andrea Ghez, UCLA professor of physics and astronomy and a co-senior author of the research.
"It's usually a pretty quiet, wimpy black hole on a diet. We don't know what is driving this big feast."
Do and his team took observations of the galactic centre using the WM Keck Observatory in Hawaii over four nights earlier this year. The strange brightening was observed on May 13, and the team managed to capture it in a timelapse, two hours condensed down to a few seconds.

Quote:
Here's a timelapse of images over 2.5 hr from May from @keckobservatory of the supermassive black hole Sgr A*. The black hole is always variable, but this was the brightest we've seen in the infrared so far. It was probably even brighter before we started observing that night! pic.twitter.com/MwXioZ7twV
— Tuan Do (@quantumpenguin) August 11, 2019

That brightly glowing dot right at the beginning of the video is the dust and gas swirling around Sgr A*. Black holes themselves don't emit any radiation that can be detected by our current instruments, but the stuff nearby does when the black hole's gravitational forces generate immense friction, in turn producing radiation.
When we view that radiation with a telescope using the infrared range, it translates as brightness. Normally, the brightness of Sgr A* flickers a bit like a candle, varying from minutes to hours. But when the surroundings of a black hole flare that brightly, it's a sign something may have gotten close enough to be grabbed by its gravity.
The first frame - taken right at the beginning of the observation - is the brightest, which means Sgr A* could have been even brighter before they started observing, Do said. But no one was aware that anything was drawing close enough to be swallowed by the black hole.
The team is busily gathering data to try and narrow it down, but there are two immediate possibilities. One is G2, an object thought to be a gas cloud that approached within 36 light-hours of Sgr A* in 2014. If it was a gas cloud, this proximity should have torn it to shreds, and parts of it devoured by the black hole - yet nothing happened.
The flyby was later called a "cosmic fizzle", but the researchers believe the black hole's May fireworks show may have been a delayed reaction.
[Image: sgr-a-s02.jpg][img=700x0]https://www.sciencealert.com/images/2019-08/sgr-a-s02.jpg[/img]

(Do et al., arXiv, 2019)

But - have a look at the timelapse again. See that bright dot at around 11 o'clock from the black hole? That's S0-2, a star on a long, looping, 16-year elliptical orbit around Sgr A*. Last year, it made its closest approach, coming within 17 light-hours of the black hole.
"One of the possibilities," Do told ScienceAlert, "is that the star S0-2, when it passed close to the black hole last year, changed the way gas flows into the black hole, and so more gas is falling on it, leading it to become more variable."
The only way to find out is having more data. They are currently being collected, across a larger range of wavelengths. More observations will take place over the coming weeks with the ground-based Keck Observatory before the galactic centre is no longer visible at night from Earth.
But many other telescopes - including Spitzer, Chandra, Swift and ALMA - were observing the galactic centre over the last few months, too. Their data could reveal different aspects of the physics of the change in brightness, and help us understand what Sgr A* is up to.
"I'm eagerly awaiting their results," Do said.
The paper has been published in [i]The Astrophysical Journal Letters.[/i]


[i]https://www.sciencealert.com/our-galaxy-...t-know-why[/i]


Arrow https://www.infowars.com/heart-of-darkne...-universe/
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#3
SEPTEMBER 23, 2019 FEATURE
Theory proposes that LIGO/Virgo black holes originate from a first order phase transition
by Ingrid Fadelli , Phys.org
[Image: theorypropos.jpg]Graphic showing the observed population of black holes of mass a few tens of solar masses. Credit: LIGO-Virgo/Frank Elavsky/Northwestern.
A few years ago, the LIGO/Virgo collaboration detected gravitational waves arising from a binary black hole merger using the two detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO). This eventually led to the observation of black holes with masses that are roughly 30 times the mass of the sun. Since then, researchers worldwide have been investigating these black holes, specifically examining whether they could be of primordial origin, meaning that they were produced in the early universe before stars and galaxies were formed.

Hooman Davoudiasl, a theoretical physicist at the Brookhaven National Laboratory in New York, has recently introduced a new theory suggesting that the black holes observed by the LIGO/Virgo collaboration originate from a first order quark confinement phase transition. In his paper, published in Physical Review Letters, Davoudiasl implemented this idea using a light scalar that could turn out to be a good dark matter candidate.
Recent detections by the LIGO/Virgo collaboration suggest that there are several black holes that have similar masses (approximately 30 solar masses). This suggests that there might be a population of black holes that are characterized by a typical mass value.
"This population may be associated with stellar evolution and certain astrophysical conditions, but a primordial origin could also be a potential explanation," Hooman Davoudiasl, the researcher who carried out the study, told Phys.org. "This latter possibility is quite intriguing, but how such objects might form in the early universe is an open question."
A mechanism that could potentially lead to the production of primordial black holes (PBH) is an abrupt cosmological phase transition, which is somewhat similar to the transition from vapor to liquid that occurs when water condenses on a cold surface. An example of this phase transition in the early universe could be the cooling of hot plasma made up of quarks and gluons, which might have occurred as the universe expanded, and they began binding into protons and neutrons.
According to current physics theories, however, there are two key issues with this scenario. Firstly, the transition would not be abrupt, and secondly, it would most likely lead to the production of PBHs with a mass similar to that of the sun, rather than masses 10 or more times larger.
"In my paper, I set out to examine under what additional assumptions, from as yet unknown phenomena, the above picture can change in a way that is conducive to a 'primordial' explanation of the black hole population observed by LIGO/Virgo," Davoudiasl said.

The explanation he proposed is based on a longstanding theoretical construct suggesting that if there are three or more light quarks, the transition from the hot quark-gluon plasma to nuclear particles could, in fact, be abrupt. The current standard physics theory that has been extensively tested, however, states that in this scenario, only two quarks are sufficiently light; thus, the transition would not be abrupt (i.e., it would not be a first-order phase transition).
"My idea was to see how one can arrange for this situation to change in the early universe, so that the transition is abrupt, but then recover the standard picture later on, corresponding to well-established present-day experimental data," Davoudiasl explained.
Davoudiasl essentially wanted to show that under certain conditions corresponding to new physical ingredients, three or more light quarks could, in fact, have been present in the early universe while the transition to nuclear matter was taking place. This would ultimately entail a first-order phase transition, enabling the production of PBH with masses similar to those observed by the LIGO/Virgo collaboration.
"My proposal arranges for the quarks to attain the masses that we observe today afterwards," Davoudiasl said. "However, interestingly, by making the number of light quarks larger, one also pushes the masses of the PBHs that could be produced to larger values, closer to that of the population observed by LIGO/Virgo."
The idea introduced by Davoudiasl in his recent paper could explain the production of the PBHs observed by the LIGO/Virgo team. In addition, it could shed light on why their masses are larger than what might be expected based on current physics theories.
"Rendering the transition abrupt in the way I proposed not only facilitates the production of PBHs, but also makes their expected masses heavier, approaching those observed by LIGO/Virgo through gravitational waves," Davoudiasl added. "Also, my proposal employs a very light hypothetical particle whose dynamics control the variation of quark masses from very small to their observed values today."
Interestingly, the hypothetical "light field" considered in Davoudiasl's theory might have the right properties to be the dark matter of the universe that countless researchers have been investigating and seeking. In fact, the black holes observed by the LIGO/Virgo collaboration may only account for a small fraction of dark matter, due to various constraints.
"The general subject of non-standard cosmologies is worth thinking about further," Davoudiasl said. "Modifying some of our usual assumptions regarding the early universe could potentially lead to new insights about open questions in physics and cosmology."




Explore further
Where in the universe can you find a black hole nursery?



[b]More information:[/b] Hooman Davoudiasl. LIGO/Virgo Black Holes from a First Order Quark Confinement Phase Transition, Physical Review Letters (2019). DOI: 10.1103/PhysRevLett.123.101102

B. P. Abbott et al. Observation of Gravitational Waves from a Binary Black Hole Merger, Physical Review Letters (2016). DOI: 10.1103/PhysRevLett.116.061102
GWTC-1: A gravitational-wave transient catalog of compact binary mergers observed by LIGO and Virgo during the first and second observing runs. arXiv:1811.12907 [astro-ph.HE]. arxiv.org/abs/1811.12907
www.ligo.caltech.edu/
www.virgo-gw.eu/
[b]Journal information:[/b] Physical Review Letters

https://phys.org/news/2019-09-theory-lig...phase.html
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#4
in-duck-ted.
[Image: fig_00387_kelvinwake_2.png]
Quack.

[Image: luminet.jpg]
Quote:You can also see that one side of the accretion disc is brighter than the other. This effect is called relativistic beaming, and it's caused by the rotation of the disc. The part of the disc that is moving towards us is brighter because it is moving close to light-speed. This motion produces a change in frequency in the wavelength of the light. It's called the Doppler effect.

The side that's moving away from us, therefore, is dimmer, because that motion has the opposite effect.
"It is precisely this strong asymmetry of apparent luminosity," Luminet wrote in a paper last year, "that is the main signature of a black hole, the only celestial object able to give the internal regions of an accretion disk a speed of rotation close to the speed of light and to induce a very strong Doppler effect."
[Image: 26459820962_9db0403650_c.jpg]
SPACE
New NASA Visualisation of a Black Hole Is So Beautiful We Could Cry
[Image: black-hole-sim_1024.gif]
MICHELLE STARR
26 SEP 2019

The first-ever direct image of a black hole's event horizon was a truly impressive feat of scientific ingenuity. But it was extremely difficult to achieve, and the resulting image was relatively low-resolution.
Techniques and technology will be refined, and it's expected that future direct images of black holes will improve with time. And a new NASA visualisation - made for the agency's Black Hole Week - shows what we might expect to see in high-resolution images of an actively accreting supermassive black hole.
Supermassive black holes sit at the centres of most large galaxies, and how they got there is a mystery; which came first, the black hole or the galaxy, is one of the big questions in cosmology.
What we do know is that they are really huge, as in millions or billions of times the mass of the Sun; that they can control star formation; that when they wake up and start feeding, they can become the brightest objects in the Universe. Over the decades, we have also figured out some of their strange dynamics.[img=700x0]https://www.sciencealert.com/images/2019-09/m87_black_hole.jpg[/img][Image: m87_black_hole.jpg]

First-ever direct image of a black hole, M87*. (EHT Collaboration)

In fact, the very first simulated image of a black hole, calculated using a 1960s punch card IBM 7040 computer and plotted by hand by French astrophysicist Jean-Pierre Luminet in 1978, still looks a lot like NASA's simulation.
In both simulations (the new one above, and Luminet's work below), you see a black circle in the centre. That's the event horizon, the point at which electromagnetic radiation - light, radio waves, X-rays and so forth - are no longer fast enough to achieve escape velocity from the black hole's gravitational pull.
[Image: luminet.jpg]

(Jean-Pierre Luminet)

Across the middle of the black hole is the front of the disc of material that is swirling around the black hole, like water into a drain. It generates such intense radiation through friction that we can detect this part with our telescopes - that's what you are seeing in the picture of M87*.
You can see the photon ring, a perfect ring of light around the event horizon. And you can see a broad sweep of light around the black hole. That light is actually coming from the part of the accretion disc behind the black hole; but the gravity is so intense, even outside the event horizon, that it warps spacetime and bends the path of light around the black hole.
You can also see that one side of the accretion disc is brighter than the other. This effect is called relativistic beaming, and it's caused by the rotation of the disc. The part of the disc that is moving towards us is brighter because it is moving close to light-speed. This motion produces a change in frequency in the wavelength of the light. It's called the Doppler effect.
The side that's moving away from us, therefore, is dimmer, because that motion has the opposite effect.
"It is precisely this strong asymmetry of apparent luminosity," Luminet wrote in a paper last year, "that is the main signature of a black hole, the only celestial object able to give the internal regions of an accretion disk a speed of rotation close to the speed of light and to induce a very strong Doppler effect."
Simulations such as these can help us understand the extreme physics around supermassive black holes - and that helps us understand what we are seeing when we look at the picture of M87*.


https://www.sciencealert.com/this-new-na...-could-cry

[Image: nasavisualiz.gif]
NASA visualization shows a black hole's warped world
This new visualization of a black hole illustrates how its gravity distorts our view, warping its surroundings as if seen in a carnival mirror. The visualization simulates the appearance of a black hole where infalling matter ...

ASTRONOMY

14 HOURS AGO

68

1442

[Image: foundthreebl.jpg]
Found: three black holes on collision course
Astronomers have spotted three giant black holes within a titanic collision of three galaxies. Several observatories, including the Chandra X-ray Observatory and other NASA space telescopes, captured the unusual system.


[Image: blackholesee.jpg]
Black hole seeds missing in cosmic garden
In the vast garden of the universe, the heaviest black holes grew from seeds. Nourished by the gas and dust they consumed, or by merging with other dense objects, these seeds grew in size and heft to form the centers of galaxies, ...


ASTRONOMY
Reply
#5
...


Quote:Astronomers have spotted three giant black holes within a titanic collision of three galaxies.



Made me wonder Hmm2

 what would happen  Holycowsmile

if Whip

two black holes were placed too close to each other  Ninja Ninja

Would the larger black hole out suck the smaller black hole right out of existence?
Has that ever happened?
Sssssswallow it up?
or would they both rip each other apart ... into ... what? 

Shredding black holes apart, what manner of mass rips out from the abyss, what is ejected?

New labels.
BHMI  --- Black Hole Mass Injections  --- 
BHME --- Black Hole Mass Ejections   --- 

What kind of energy discharge would occur upon the consumption of a smaller black hole, 
into a larger black hole?

A giant hand reaches across and through the galactic expanse,
and then penetrates deep into the black hole at the center of the Milky Way,
to make a withdrawal  Hi  
30 million suns of mass glowing in the palm of my hand.

...
Reply
#6
Gargantuan Black Hole Shreds Star in Rare Cosmic 'Crime Scene'
By Tariq Malik - Space.com Managing Editor 14 hours ago Space 
R.I.P. ASASSN-19bt. We hardly knew you.

Videos:  Arrow  https://www.livescience.com/giant-black-...-star.html

 [Image: QacKEhCum8VXnz2sWcWWE-650-80.jpg]
Scientists used NASA's TESS space telescope to spot a star being shredded by a supermassive black hole. This artist’s conception depicts the star being torn apart into a thin stream of gas that is pulled around the black hole before crashing back into the star, kicking off more material. 
(Image credit: Robin Dienel, courtesy of Carnegie Institution for Science)
A NASA space telescope hunting for alien planets just stumbled into a rare cosmic crime scene: a star being devoured by a monster black hole
The discovery, made by NASA's Transiting Exoplanet Survey Satellite (TESS), provides a rare glimpse into the death throes of a star as it is torn apart by the cataclysmic gravitational forces of a supermassive black hole. The action's happening about 375 million light-years away from Earth in the direction of the constellation Volans (the fish). 
The star and black hole, known together as ASASSN-19bt, is what scientists call a tidal disruption event, or TDE, in which a black hole's gravity rips gas from a star, flinging some into space. The rest forms a bright disk that gradually falls into the black hole, researchers said.
Video: Watch a Black Hold Shred the ASASSN-19bt Star!
Related:
 Where Do Black Holes Lead?
"Only a handful of TDEs have been discovered before they reached peak brightness, and this one was found just a few days after it started to brighten," said astronomer Thomas Holoien, of the Carnegie Institution for Science in Washington, D.C., in a statement.

https://www.livescience.com/giant-black-...-star.html
 

Holoien said NASA's TESS, which looks for dips in the brightness of stars to identify potential planets, observed ASASSN-19bt every half-hour for months, providing a blow-by-blow account of the star's destruction.
"This makes ASASSN-19bt the new poster child for TDE research," said Holoien, a founding member of The Ohio State University's All-Sky Automated Survey for Supernovae (ASAS-SN), which made the find using TESS observations.
Holoien and colleagues used TESS data along with observations from other space telescopes and ground-based observatories to piece together the story of ASASSN-19bt's star demise for months in early 2019. They tracked it for 42 days before it reached peak brightness in March and then followed it for another 37 days as it faded, with additional observations made over the following months.
The research is detailed in the Sept. 26 edition of The Astrophysical Journal and also appears in the preprint website arXiv.org here.
Related: No Escape: Dive into a Black Hole (Infographic)
"Having so much data about ASASSN-19bt will allow us to improve our understanding of the physics at work when a star is unlucky enough to meet a black hole," said Decker French, a Carnegie astronomer and a member of the study team, in the statement.
videoes: Arrow https://www.livescience.com/giant-black-...-star.html
[img=602x0]https://vanilla.futurecdn.net/livescience/media/img/missing-image.svg[/img]
[Image: dtPwgfnabdo4mmKjNxrPG5-650-80.jpg]
This NASA artist's illustration shows the tail of gas from a star stripped away by a supermassive black hole until it forms a bright ring of infalling matter as seen in ASASSN-19bt by the TESS space telescope.
https://www.livescience.com/giant-black-...-star.html
(Image credit: NASA's Goddard Space Flight Center)
Researchers found that ASASSN-19bt's host galaxy appears younger and dustier than those containing other TDEs found in previous studies. The team also spotted a "short blip" of cooling and fading before the TDE's temperature leveled off and began to brighten to its peak brilliance, the team reported.
The scientists were also able to measure the light from ASASSN-19bt's star to learn more about the object's composition, even as the star was ripped apart.
"It was once thought that all TDEs would look the same. But it turns out that astronomers just needed the ability to make more detailed observations of them," Ohio State astronomer Patrick Vallely, the second author on the study, said in the statement. "We have so much more to learn about how they work, which is why capturing one at such an early time and having the exquisite TESS observations was crucial."
NASA's TESS space telescope launched in April 2018 to search for alien planets around distant stars. To date, the space telescope has spotted 24 confirmed exoplanets and 993 other candidate worlds.
ASASSN-19bt is not the only nonplanet discovery from TESS. The space telescope has also observed a comet in our solar system, found more evidence for exocomets around the star Beta Pictoris 63 light-years from Earth and spotted at least six exploding stars (called supernovas) during its first few months of operation.


https://www.livescience.com/giant-black-...-star.html
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SEPTEMBER 30, 2019 REPORT
Planet Nine could be a primodial black hole, new research suggests
by Tomasz Nowakowski , Phys.org
[Image: planetnineco.jpg]Artist's concept of the hypothetical Planet Nine. Credit: Caltech/R. Hurt (IPAC)
The hypothetical Planet Nine, assumed to be lurking somewhere in the outskirts of our solar system, may not be a planet at all. A new study, published September 24 on the arXiv pre-print server, suggests that the mysterious and still undiscovered object might be a primodial black hole.

Primodial black holes (PBHs) are old and relatively small black holes that emerged soon after the Big Bang. They are thought to have been formed as a result of density fluctuations in the very early universe. It is believed that PBHs with the lowest mass have likely evaporated. However, those with larger masses may still exist, evaporating at the present epoch—even though they have been never directly observed.
Astronomers Jakub Scholtz of Durham University and James Unwin of University of Illinois at Chicago, assume that PBHs could reside even closer to us than we think. In a recently published paper, they ponder the possibility that the elusive Planet Nine, theorized to be orbiting the sun at a distance between 300 and 1,000 AU, could be such an old and compact black hole.
Explaining their intriguing hypothesis, the researchers focus on two unsolved gravitational anomalies of similar mass: anomalous orbits of trans-Neptunian objects (TNOs) and an excess in microlensing events. What is interesting is that both events are due to objects with masses estimated to be between 0.5 and 20 Earth masses.
The anomalies of TNO orbits are assumed to be triggered by a new gravitational source in the outer solar system. While it is widely accepted that this source could be a free-floating planet, Scholtz and Unwin argue that the PBH scenario is not unreasonable and should be taken into account.
"Capture of a free-floating planet is a leading explanation for the origin of Planet Nine, and we show that the probability of capturing a PBH instead is comparable," the astronomers wrote in the paper.
However, it could be difficult to confirm this theory, as such a hypothetical PBH, with a mass of around five Earth masses and a radius of about five centimeters, would have a Hawking temperature of approximately 0.004 K, making it colder than the cosmic microwave background (CMB). Therefore, the power radiated by a typical PBH alone is minuscule, which makes it hard to detect.
In order to overcome this obstacle, the authors of the paper propose to search for annihilation signals from the dark matter microhalo around a PHB. Such a dark matter halo, if annihilating, is thought to be able to provide a powerful signal that could be identified by observations. Hence, the astronomers suggest dedicated searches for moving sources in X-rays, gamma-rays and also other high-energy cosmic rays, which could provide more evidence supporting the PHB hypothesis.




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Theory proposes that LIGO/Virgo black holes originate from a first order phase transition



[b]More information:[/b] Jakub Scholtz, James Unwin. What if Planet 9 is a Primordial Black Hole? arXiv:1909.11090v1 [hep-ph]: arxiv.org/abs/1909.11090



https://phys.org/news/2019-09-planet-pri...-hole.html
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NOVEMBER 1, 2019 FEATURE
Numerical evidence for the merger of MOTSs inside a binary black hole
by Ingrid Fadelli , Phys.org
[Image: numericalevi.jpg]
I jest itza Sheepvesica
 pi eye sees  Reefer  picis     The initial sketch outlining the idea behind the study, made by Erik Schnetter.
[Image: 26459820962_9db0403650_c.jpg]
Researchers at the Max Planck Institute for Gravitational Physics, Rochester Institute of Technology and the Perimeter Institute for Theoretical Physics have recently gathered strong numerical evidence for a new phenomenon that takes place in the interior of binary black holes. In their study, published in Physical Review Letters, they collected observations that could offer exciting new insight into the merger of marginally outer trapped surfaces (MOTSs) in a binary black hole (BBH), a system consisting of two black holes in close orbit around each other.

"It is an underappreciated fact that event horizons are not really very useful for studying astrophysical properties of black hole mergers," the researchers told Phys.org via email. "What is much more useful are surfaces which go under the boring name of marginally outer trapped surfaces (marginal surfaces or MOTS in short). This uninteresting name hides their importance in understanding black holes."
Over the past 15 to 20 years, two of the authors of the recent paper, Badri Krishnan and Erik Schnetter, have developed ways of using marginal surfaces to calculate, among other things, black hole mass and angular momentum. Despite their achievements in this area, they were unable to answer a key question: do MOTSs merge in a BBH coalescence, and if so, how, exactly?
The researchers were keen to find out more about this merger, as well as to unveil any interesting topological features that may be hidden within it. Daniel Pook-Kolb, another author of the paper and a Ph.D. student at the Max Planck Institute, thus decided to investigate this topic further in his thesis.
"To understand the merger, we need to locate very highly distorted marginal surfaces, a numerically challenging task that defeated all previous studies," the researchers said. "We developed a new numerical technique for this task and got ever closer to the merger point. Still, even our methods do not work extremely close to the merger, where surfaces with cusps appear."
As the researchers were unable to gain the insight they were looking for in their previous studies, they continued looking for different routes to investigate the merger of MOTSs in a BBH system. Eventually, Schnetter came up with a new idea for approaching this topic, which entailed looking for surfaces with intersecting loops.
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Credit: Pook-Kolb et al.
When he proposed this to the rest of the team, Krishnan was somewhat skeptical, as no previous literature had explored this idea before, but Pook-Kolb decided to investigate it regardless and look for such surfaces. Eventually it turned out that such topological features do exist, and that they could, in fact, be generic features of black hole mergers.

Essentially, the researchers simulated the head-on collision of two non-spinning black holes with unequal masses. In these simulations, they observed that the MOTS associated with the final black hole resulting from a BBH merger unites with the two initially disjoint surfaces that correspond to the two initial black holes in the system.
This results in a connected sequence of MOTSs interpolating between the initial and final state of the BBH, up until the merger between the two black holes eventually takes place. Ultimately, their findings highlight a topology change in the merge of marginal surfaces.
The observations gathered in their simulations also hint to the existence of a MOTS with self-intersections that is formed immediately after the merger. The researchers, however, expect that another one of their findings will have far greater implications for future gravitational wave observations.
"Since we now have a sequence of marginal surfaces taking us from the two initially disjoint black holes to the final one, we can calculate in detail how physical quantities of black holes behave during the merger," the researchers said. "It would be especially interesting to find similar features in the observed gravitational wave signals: We can then rightfully claim to observationally understand what happens inside a black hole event horizon."
The numerical evidence gathered by Pook-Kolb, Schnetter, Krishnan and their colleague Ofek Birnholtz offers fascinating new insights about BBH mergers. In the future, their observations could pave the way for new studies, including attempts to prove mathematically the Penrose inequality for generic astrophysical BBH configurations.
The researchers are now planning to try generalizing their idea to other black hole mergers, such as those observed by the LIGO collaboration. This could make the theory they came up with usable by a much larger research community.
"Work on generalizing our idea to generic mergers is underway, and the first results building on the same theory are now coming up," the researchers said. "We are extremely excited to see what awaits us in simulations of fully general realistic mergers!"




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Where in the universe can you find a black hole nursery?



[b]More information:[/b] Daniel Pook-Kolb et al. Interior of a Binary Black Hole Merger, Physical Review Letters (2019). DOI: 10.1103/PhysRevLett.123.171102
[b]Journal information:[/b] Physical Review Letters



https://phys.org/news/2019-11-numerical-...inary.html





The Universe Might Be a Giant Loop
By Rafi Letzter - Staff Writer 8 hours ago Space 
What shape is space?
[*][Image: kZmWHxmiGaUZm9at4L3SNo-320-80.png]Early data from the Planck collaboration maps the cosmic microwave background across the sky.
(Image: © ESA and the Planck Collaboration)


Everything we think we know about the shape of the universe could be wrong. Instead of being flat like a bedsheet, our universe may be curved, like a massive, inflated balloon, according to a new study.
That's the upshot of a new paper published today (Nov. 4) in the journal [url=https://www.nature.com/articles/s41550-019-0906-9]Nature Astronomy
, which looks at data from the cosmic microwave background (CMB), the faint echo of the Big Bang. But not everyone is convinced; the new findings, based on data released in 2018, contradict both years of conventional wisdom and another recent study based on that same CMB data set.
Related: From Big Bang to Present: Snapshots of Our Universe Through Time
If the universe is curved, according to the new paper, it curves gently. That slow bending isn't important for moving around our lives, or solar system, or even our galaxy. But travel beyond all of that, outside our galactic neighborhood, far into the deep blackness, and eventually — moving in a straight line — you'll loop around and end up right back where you started. Cosmologists call this idea the "closed universe." It's been around for a while, but it doesn't fit with existing theories of how the universe works. So it's been largely rejected in favor of a "flat universe" that extends without boundary in every direction and doesn't loop around on itself. Now, an anomaly in data from the best-ever measurement of the CMB offers solid (but not absolutely conclusive) evidence that the universe is closed after all, according to the authors: University of Manchester cosmologist Eleonora Di Valentino, Sapienza University of Rome cosmologist Alessandro Melchiorri and Johns Hopkins University cosmologist Joseph Silk.

[*]
The difference between a closed and open universe is a bit like the difference between a stretched flat sheet and an inflated balloon, Melchiorri told Live Science. In either case, the whole thing is expanding. When the sheet expands, every point moves away from every other point in a straight line. When the balloon is inflated, every point on its surface gets farther away from every other point, but the balloon's curvature makes the geometry of that movement more complicated.
"This means, for example, that if you have two photons and they travel in parallel in a closed universe, they will [eventually] meet," Melchiorri said.
In an open, flat universe, the photons, left undisturbed, would travel along their parallel courses without ever interacting.
The conventional model of the universe's inflation, Melchiorri said, suggests that the universe should be flat. Rewind the expansion of space all the way to the beginning, to the first 0.0000000000000000000000001 seconds after the Big Bang, according to that model, and you'll see a moment of incredible, exponential expansion as space grew out of that infinitesimal point in which it began. And the physics of that superfast expansion point to a flat universe. That's the first reason most experts believe the universe is flat, he said. If the universe isn't flat, you have to "fine-tune" the physics of that primordial mechanism to make it all fit together — and redo countless other calculations in the process, Melchiorri said.
But that might end up being necessary, the authors wrote in the new study.
That's because there's an anomaly in the CMB. The CMB is the oldest thing we see in the universe, made of ambient microwave light that suffuses all of space when you block out the stars and galaxies and other interference. It's one of the most important sources of data on the universe's history and behavior, because it's so old and so spread throughout space. And it turns out, according to the latest data, that there's significantly more "gravitational lensing" of the CMB than expected — meaning that gravity seems to be bending the microwaves of the CMB more than existing physics can explain.
The data the team is drawing upon comes from a 2018 release from the Planck experiment — a European Space Agency (ESA) experiment to map the CMB in more detail than ever before. (The new data will be published in a forthcoming issue of the journal Astronomy & Astrophysics and is available now on the ESA website. Both Di Valentino and Melchiorri were part of that effort as well.)
To explain that extra lensing, the Planck Collaboration has just tacked on an extra variable, which the scientists are calling "A_lens," to the group's model of the universe's formation, "This is something that you put there by hand, trying to explain what you see. There's no connection with physics," Melchiorri said, meaning there's no A_lens parameter in Einstein's theory of relativity. "What we found is that you can explain A_lens with a positively curved universe, which is a much more physical interpretation that you can explain with general relativity."
Melchiorri pointed out that his team's interpretation isn't conclusive. According to the group's calculations, the Planck data point to a closed universe with a standard deviation of 3.5 sigma (a statistical measurement that means about 99.8% confidence that the result isn't due to random chance). That's well short of the 5 sigma standard physicists usually look for before calling an idea confirmed.
But some cosmologists said there were even more reasons to be skeptical.
Andrei Linde, a cosmologist at Stanford University, told Live Science that the Nature Astronomy paper failed to take into account another important paper, published to the arXiv database on Oct. 1. (That paper has not yet been published in a peer reviewed journal.)
In that paper, University of Cambridge cosmologists George Efstathiou and Steven Gratton, who both also worked on the Planck Collaboration, looked at a narrower subset of data than the Nature Astronomy paper. Their analysis also supported a curving universe, but with much less statistical confidence than Di Valentino, Melchiorri and Silk found looking at a larger segment of the Planck data. However, when Efstathiou and Graton looked at the data together with two other existing data sets from the early universe, they found that overall, the evidence pointed toward a flat universe.
Asked about the Efstathiou and Gratton paper, Melchiorri praised the careful treatment of the work. But he said the duo's analysis relies on too small a segment of the Planck data. And he pointed out that their research is based on a modified (and, in theory, improved) version the Planck data — not the public data set that more than 600 physicists had vetted.
Linde pointed to that reanalysis as a sign that Efstathiou and Gratton's paper was based on better methods.
Efstathiou asked not to be directly quoted, but pointed out in an email to Live Science that if the universe were curved, it would raise a number of problems — contradicting those other data sets from the early universe and making discrepancies in the  universe's observed rate of expansion much worse. Gratton said he agreed.
Melchiorri also agreed that the closed-universe model would raise a number of problems for physics. 
"I don't want to say that I believe in a closed universe," he said. "I'm a little bit more neutral. I'd say, let's wait on the data and what the new data will say. What I believe is that there's a discrepancy now, that we have to be careful and try to find what is producing this discrepancy."

https://www.livescience.com/universe-may-be-curved.html
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Quote:In this new effort, the researchers built on prior research that suggests that because of the nature of black holes, it is likely that those that exist near the center of a galaxy would migrate towards a ring that exists around the supermassive black hole that exists at the center. Such black holes would become trapped in the ring and would congregate in what is known as an active galactic nucleus. In such a scenario, it is likely that one of the black holes would move close enough to another for the two to become attracted to one another, eventually winding up with a merger. Under such a scenario, it would be possible for multiple mergers to occur with the same black hole, resulting in it becoming bigger and bigger. To test the theory, the researchers input data describing such action into a computer and via simulations used it to estimate the probability of larger than normal black holes coming into existence. They report that the simulations showed it should be possible for larger than normal black holes to form under such conditions, in the range 60 to 80 solar masses. The team also found that such black holes would spin in the direction opposite of their orbiting motion.




NOVEMBER 6, 2019 REPORT
Simulations show how massive black holes could be formed by mergers
by Bob Yirka , Phys.org
[Image: blackhole.jpg]This computer-simulated image shows a supermassive black hole at the core of a galaxy. The black region in the center represents the black hole's event horizon, where no light can escape the massive object's gravitational grip. The black hole's powerful gravity distorts space around it like a funhouse mirror. Light from background stars is stretched and smeared as the stars skim by the black hole. Credit: NASA, ESA, and D. Coe, J. Anderson, and R. van der Marel (STScI)
A team of researchers affiliated with several institutions in the U.S. along with one in India and one in Hungary has created simulations that could explain how larger than expected black holes could form near supermassive black holes at the center of galaxies. In their paper published in the journal Physical Review Letters, the group describes how they made their simulations and what they showed.

Prior research has shown that it is likely that black holes that form due to the death of a star cannot exceed 40 solar masses—more massive stars would have more nuclei which suggests they would wind up as pairs of unstable supernovae. But researchers working at the LIGO and VIRGO projects have found evidence of black holes that are bigger than the 40 solar mass threshold. Some in the field have proposed that such black holes could come about due to random collisions and mergers with other black holes—but the idea has not been fully developed until now.
In this new effort, the researchers built on prior research that suggests that because of the nature of black holes, it is likely that those that exist near the center of a galaxy would migrate towards a ring that exists around the supermassive black hole that exists at the center. Such black holes would become trapped in the ring and would congregate in what is known as an active galactic nucleus. In such a scenario, it is likely that one of the black holes would move close enough to another for the two to become attracted to one another, eventually winding up with a merger. 

[Image: numericalevi.jpg]
Under such a scenario, it would be possible for multiple mergers to occur with the same black hole, resulting in it becoming bigger and bigger. 


Quote:I jest itza [Image: sheep.gif]vesica

 pi eye sees  [Image: reefer.gif]  picis 

I jest itza [Image: sheep.gif]vesica

 pi eye sees  [Image: reefer.gif]  a thrice-is 


To test the theory, the researchers input data describing such action into a computer and via simulations used it to estimate the probability of larger than normal black holes coming into existence. They report that the simulations showed it should be possible for larger than normal black holes to form under such conditions, in the range 60 to 80 solar masses. The team also found that such black holes would spin in the direction opposite of their orbiting motion.




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Another way for stellar-mass black holes to grow larger



[b]More information:[/b] Y. Yang et al. Hierarchical Black Hole Mergers in Active Galactic Nuclei, Physical Review Letters (2019). DOI: 10.1103/PhysRevLett.123.181101
[b]Journal information:[/b] Physical Review Letters 




https://phys.org/news/2019-11-simulation...rgers.html
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Quote:The discovery came as a big surprise. "Black holes of such mass should not even exist in our galaxy, according to most of the current models of stellar evolution," said Prof. LIU. "We thought that very massive stars with the chemical composition typical of our galaxy must shed most of their gas in powerful stellar winds, as they approach the end of their life. Therefore, they should not leave behind such a massive remnant. LB-1 is twice as massive as what we thought possible. Now theorists will have to take up the challenge of explaining its formation."


NOVEMBER 27, 2019
Scientists discover unpredicted stellar black hole
[Image: chineseacade.jpg]Accretion of gas onto a stellar black hole from its blue companion star, through a truncated accretion disk (Artist impression). Credit: YU Jingchuan, Beijing Planetarium, 2019.
An international team headed by Professor LIU Jifeng of the National Astronomical Observatory of China of the Chinese Academy of Sciences (NAOC) spotted a stellar black hole with a mass 70 times greater than the sun. The monster black hole is located 15,000 light-years from Earth and has been named LB-1 by the researchers.

The Milky Way galaxy is estimated to contain 100 million stellar black holes—cosmic bodies formed by the collapse of massive stars and so dense even light can't escape. Until now, scientists had estimated the mass of an individual stellar black hole in our galaxy at no more than 20 times that of the sun. But the discovery of a huge black hole by a Chinese-led team of international scientists has toppled that assumption.
The team, headed by Prof. LIU Jifeng of the National Astronomical Observatory of China of the Chinese Academy of Sciences (NAOC), spotted a stellar black hole with a mass 70 times greater than the sun. The monster black hole is located 15 thousand light-years from Earth and has been named LB-1 by the researchers. The discovery is reported in the latest issue of Nature.
The discovery came as a big surprise. "Black holes of such mass should not even exist in our galaxy, according to most of the current models of stellar evolution," said Prof. LIU. "We thought that very massive stars with the chemical composition typical of our galaxy must shed most of their gas in powerful stellar winds, as they approach the end of their life. Therefore, they should not leave behind such a massive remnant. LB-1 is twice as massive as what we thought possible. Now theorists will have to take up the challenge of explaining its formation."
Until just a few years ago, stellar black holes could only be discovered when they gobbled up gas from a companion star. This process creates powerful X-ray emissions, detectable from Earth, that reveal the presence of the collapsed object.
The vast majority of stellar black holes in our galaxy are not engaged in a cosmic banquet, though, and thus don't emit revealing X-rays. As a result, only about two dozen galactic stellar black holes have been well identified and measured.
To counter this limitation, Prof. LIU and collaborators surveyed the sky with China's Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), looking for stars that orbit an invisible object, pulled by its gravity.
This observational technique was first proposed by the visionary English scientist John Michell in 1783, but it has only become feasible with recent technological improvements in telescopes and detectors. Still, such a search is like looking for the proverbial needle in a haystack: only one star in a thousand may be circling a black hole.
After the initial discovery, the world's largest optical telescopes—Spain's 10.4-m Gran Telescopio Canarias and the 10-m Keck I telescope in the United States—were used to determine the system's physical parameters. The results were nothing short of fantastic: A star eight times heavier than the sun was orbiting a 70-solar-mass black hole every 79 days.
The discovery of LB-1 fits nicely with another breakthrough in astrophysics. Recently, the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo gravitational wave detectors have begun to catch ripples in spacetime caused by collisions of black holes in distant galaxies. Intriguingly, the black holes involved in such collisions are also much bigger than what was previously considered typical.
The direct sighting of LB-1 proves that this population of over-massive stellar black holes exists even in our own backyard. "This discovery forces us to re-examine our models of how stellar-mass black holes form," said LIGO Director Prof. David Reitze from the University of Florida in the U.S.
"This remarkable result along with the LIGO-Virgo detections of binary black hole collisions during the past four years really points towards a renaissance in our understanding of black hole astrophysics," said Reitze.




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Image: Black hole bounty captured in the center of the Milky Way



[b]More information:[/b] A wide star–black-hole binary system from radial-velocity measurements , Nature (2019). DOI: 10.1038/s41586-019-1766-2 , https://nature.com/articles/s41586-019-1766-2
[b]Journal information:[/b] Nature [/url]

Provided by 
Chinese Academy of Sciences 



https://phys.org/news/2019-11-scientists...-hole.html





NOVEMBER 27, 2019
A new theory for how black holes and neutron stars shine bright
[Image: anewtheoryfo.jpg]Here, a massive super-computer simulation shows the strong particle density fluctuations that occur in the extreme turbulent environments that host black holes and neutron stars. Dark blue regions are low particle density regions, while yellow regions are strongly over-dense regions. Particles are accelerated to extremely high speeds due to the interactions with strongly turbulence fluctuations in this environment. Credit: Image from published study
For decades, scientists have speculated about the origin of the electromagnetic radiation emitted from celestial regions that host black holes and neutron stars—the most mysterious objects in the universe.

Astrophysicists believe that this high-energy radiation—which makes neutron stars and black holes shine bright—is generated by electrons that move at nearly the speed of light, but the process that accelerates these particles has remained a mystery.
Now, researchers at Columbia University have presented a new explanation for the physics underlying the acceleration of these energetic particles.
In a study published in the December issue of The Astrophysical Journal, astrophysicists Luca Comisso and Lorenzo Sironi employed massive super-computer simulations to calculate the mechanisms that accelerate these particles. They concluded that their energization is a result of the interaction between chaotic motion and reconnection of super-strong magnetic fields.
"Turbulence and magnetic reconnection—a process in which magnetic field lines tear and rapidly reconnect—conspire together to accelerate particles, boosting them to velocities that approach the speed of light," said Luca Comisso, a postdoctoral research scientist at Columbia and first author on the study.
"The region that hosts black holes and neutron stars is permeated by an extremely hot gas of charged particles, and the magnetic field lines dragged by the chaotic motions of the gas, drive vigorous magnetic reconnection," he added. "It is thanks to the electric field induced by reconnection and turbulence that particles are accelerated to the most extreme energies, much higher than in the most powerful accelerators on Earth, like the Large Hadron Collider at CERN."
When studying turbulent gas, scientists cannot predict chaotic motion precisely. Dealing with the mathematics of turbulence is difficult, and it constitutes one of the seven "Millennium Prize" mathematical problems. To tackle this challenge from an astrophysical point of view, Comisso and Sironi designed extensive super-computer simulations —among the world's largest ever done in this research area—to solve the equations that describe the turbulence in a gas of charged particles.

[Image: 1-anewtheoryfo.jpg]
The rapidly spinning neutron star embedded in the center of the Crab nebula is the dynamo powering the nebula's eerie interior bluish glow. The blue light comes from electrons whirling at nearly the speed of light around magnetic field lines from the neutron star. The neutron star, the crushed ultra-dense core of the exploded star, like a lighthouse, ejects twin beams of radiation that appear to pulse 30 times a second. Credit: NASA, ESA, J. Hester (Arizona State University)
"We used the most precise technique—the particle-in-cell method—for calculating the trajectories of hundreds of billions of charged particles that self-consistently dictate the electromagnetic fields. And it is this electromagnetic field that tells them how to move," said Sironi, assistant professor of astronomy at Columbia and the study's principal investigator.

Sironi said that the crucial point of the study was to identify role magnetic reconnection plays within the turbulent environment. The simulations showed that reconnection is the key mechanism that selects the particles that will be subsequently accelerated by the turbulent magnetic fields up to the highest energies.
The simulations also revealed that particles gained most of their energy by bouncing randomly at an extremely high speed off the turbulence fluctuations. When the magnetic field is strong, this acceleration mechanism is very rapid. But the strong fields also force the particles to travel in a curved path, and by doing so, they emit electromagnetic radiation.
"This is indeed the radiation emitted around black holes and neutron stars that make them shine, a phenomenon we can observe on Earth," Sironi said.
The ultimate goal, the researchers said, is to get to know what is really going on in the extreme environment surrounding black holes and neutron stars, which could shed additional light on fundamental physics and improve our understanding of how our Universe works.
They plan to connect their work even more firmly with observations, by comparing their predictions with the electromagnetic spectrum emitted from the Crab Nebula, the most intensely studied bright remnant of a supernova (a star that violently exploded in the year 1054). This will be a stringent test for their theoretical explanation.
"We figured out an important connection between turbulence and magnetic reconnection for accelerating particles, but there is still so much work to be done," Comisso said. "Advances in this field of research are rarely the contribution of a handful of scientists, but they are the result of a large collaborative effort."
Other researchers, such as the Plasma Astrophysics group at the University of Colorado Boulder, are making important contributions in this direction, Comisso said.




Explore further
Mix master: Modeling magnetic reconnection in partially ionized plasma



[b]More information:[/b] Luca Comisso et al, The Interplay of Magnetically Dominated Turbulence and Magnetic Reconnection in Producing Nonthermal Particles, The Astrophysical Journal (2019). DOI: 10.3847/1538-4357/ab4c33
[b]Journal information:[/b] Astrophysical Journal 

Provided by Columbia University







NOVEMBER 27, 2019
Evidence for anisotropy of cosmic acceleration
[Image: evidencefora.jpg]The cosmic ‘deceleration parameter’ inferred from the JLA catalogue of Type Ia supernovae is negative (i.e. the expansion rate is accelerating), but it is mainly a dipole (qd), i.e., in a specific direction, while its monopole (qm) component is close to zero. The current standard cosmological model (indicated by a blue star) which has qm = -0.55, qd = 0, is excluded at over 4σ. Credit: Astronomy & Astrophysics
The observed acceleration of the Hubble expansion rate has been attributed to a mysterious "dark energy" which supposedly makes up about 70% of the universe. Professor Subir Sarkar from the Rudolf Peierls Centre for Theoretical Physics, Oxford along with collaborators at the Institut d'Astrophysique, Paris and the Niels Bohr Institute, Copenhagen have used observations of 740 Type Ia supernovae to show that this acceleration is a relatively local effect—it is directed along the direction we seem to be moving with respect to the cosmic microwave background (which exhibits a similar dipole anisotropy). While the physical reason for this acceleration is unknown, it cannot be ascribed to dark energy which would have caused equal acceleration in all directions.

Professor Sarkar explains: "The cosmological standard model rests on the assumption that the Universe is isotropic around all observers. This cosmological principle is an extension of the Copernican principle—namely that we are not privileged observers. It affords a vast simplification in the mathematical construction of the cosmological model using Einstein's theory of general relativity. However when observational data are interpreted within this framework we are led to the astonishing conclusion that about 70% of the universe is constituted of Einstein's Cosmological Constant or more generally "dark energy." This has been interpreted as due to quantum zero-point fluctuations of the vacuum but the associated energy scale is set by H0, the present rate of expansion of the universe. This is however a factor of 1044 below the energy scale of the standard model of particle physics—the well-established quantum field theory that precisely describes all subatomic phenomena. Its zero-point fluctuations have therefore a huge energy density which would have prevented the universe from reaching its present age and size if they indeed influence the expansion rate via gravity. To this cosmological constant problem must be added the "why now?" problem, namely why has dark energy come to dominate the universe only recently? It was negligible at earlier times, in particular at an age of ~400,000 years when the primordial plasma cooled sufficiently to form atoms and the cosmic microwave background (CMB) radiation was released (hence the CMB is not directly sensitive to dark energy)."
It is against this background that he, along with Jacques Colin and Roya Mohayaee (Institut d'Astrophysique, Paris) and Mohamed Rameez (Niels Bohr Institute, Copenhagen), set out to examine whether dark energy really exists. The primary evidence—rewarded with the 2011 Nobel prize in physics—concerns the "discovery of the accelerated expansion of the universe through observations of distant supernovae" in 1998 by two teams of astronomers. This was based on observations of about 60 Type Ia supernovae, but meanwhile, the sample had grown, and in 2014, the data was made available for 740 objects scattered over the sky (Joint Lightcurve Analysis catalog).

The researchers looked to see if the inferred acceleration of the Hubble expansion rate was uniform over the sky.
"First, we worked out the supernova redshifts and apparent magnitudes as measured (in the heliocentric system), undoing the corrections that had been made in the JLA catalog for local 'peculiar' (non-Hubble) velocities. This had been done to determine their values in the CMB frame in which the universe should look isotropic—however, previous work by our team had shown that such corrections are suspect because peculiar velocities do not fall off with increasing distance, hence there is no convergence to the CMB frame even as far out as a billion light years," says Professor Sarkar.

[Image: 1-evidencefora.jpg]
Within uncertainties the acceleration vector is aligned with the dipole in the cosmic microwave background radiation (indicated as a black star). Credit: Astronomy & Astrophysics
[b]Dark energy[/b]
"When we then employed the standard maximum likelihood estimator statistic to extract parameter values, we made an astonishing finding. The supernova data indicate, with a statistical significance of 3.9σ, a dipole anisotropy in the inferred acceleration (see figure) in the same direction as we are moving locally, which is indicated by a similar, well-known, dipole in the CMB. By contrast, any isotropic (monopole) acceleration that can be ascribed to dark energy is 50 times smaller and consistent with being zero at 1.4σ. By the Bayesian information criterion, the best fit to the data has, in fact, no isotropic component. We showed that allowing for evolution with redshift of the parameters used to fit the supernova light curves does not change the conclusion—thus refuting previous criticism of our method.
"Our analysis is data-driven but supports the theoretical proposal due to Christos Tsagas (University of Thessaloniki) that acceleration may be inferred when we are not Copernican observers, as is usually assumed, but are embedded in a local bulk flow shared by nearby galaxies, as is, indeed, observed. This is unexpected in the standard cosmological model, and the reason for such a flow remains unexplained. But independently of that, it appears that the acceleration is an artifact of our local flow, so dark energy cannot be invoked as its cause.
"There are, indeed, other probes of our expansion history, e.g. the imprint of baryon acoustic oscillations (BAO) in the distribution of galaxies, the ages of the oldest stars, the rate of growth of structure, etc., but such data is still too sparse, and presently equally well consistent with a non-accelerating universe. The precisely measured temperature fluctuations in the CMB are not directly sensitive to dark energy, although its presence is usually inferred from the sum rule that while the CMB measures the spatial curvature of the universe to be close to zero, its matter content does not add up to the critical density to make it so. This is, however, true only under the assumptions of exact homogeneity and isotropy—which are now in question."
Professor Sarkar concludes: "But progress will soon be made. The Large Synoptic Survey Telescope will measure many more supernovae and confirm or rule out a dipole in the deceleration parameter. The Dark Energy Spectroscopic Instrument and Euclid satellite will measure BAO and lensing precisely. The European Extremely Large Telescope will measure the 'redshift drift' of distant sources over a period of time, and thus make a direct measurement of the expansion history of the universe."




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Dark energy: new experiment may solve one of the universe's greatest mysteries



[b]More information:[/b] Jacques Colin et al. Evidence for anisotropy of cosmic acceleration, Astronomy & Astrophysics (2019). DOI: 10.1051/0004-6361/201936373
[b]Journal information:[/b] Astronomy & Astrophysics 

Provided by [url=https://phys.org/partners/oxford-university/]University of Oxford

https://phys.org/news/2019-11-evidence-a...osmic.html






NOVEMBER 26, 2019 FEATURE
A new framework could aid the search for heavy thermal dark matter
by Ingrid Fadelli , Phys.org
[Image: 3-anewframewor.jpg]Figure outlining the mechanism proposed by the researchers. Credit: Kim & Kuflik.
Astrophysicists have been searching for dark matter for several decades, but these searches have so far yielded disappointing results. In a recent study, two researchers at Weizmann Institute of Science and the Hebrew University of Jerusalem in Israel have introduced a new theoretical framework outlining a mechanism of elementary thermal dark matter with a mass up to 1014 GeV.

The dark matter considered in their work consists of several almost degenerate particles that scatter in the nearest-neighbor chain in a way that is aligned with the standard model used in dark matter studies. The new framework presented by these researchers, outlined in a paper published in Physical Review Letters, could ultimately inform future searches for heavy dark matter.
"The nature of dark matter is a longstanding problem in modern day physics," Hyungjin Kim, one of the researchers who carried out the study, told Phys.org. "A particle that is as heavy as Higgs boson, and is involved in interactions whose strength is that of electroweak interaction, is thought to be a particularly well-motivated dark matter candidate, as it often naturally arises when addressing another key problem: the hierarchy between the electroweak scale and the Planck scale."
The particle that is thought to be a good dark matter candidate, known as a weakly interacting massive particle (WIMP), could be produced naturally from interactions between standard model particles in the early universe while they are in thermal equilibrium. This particular process goes by the name of the 'thermal freeze-out mechanism."
Based on current astrophysics theory, the final abundance of WIMPs in our universe today would thus be insensitive to details of initial conditions or model parameters. However, a common lore originating from a 1990 paper by Kim Griest and Marc Kamionkowski suggests that this thermal freeze-out mechanism does not work when dark matter is heavier than 100 TeV (i.e., a thousand times heavier than the Higgs boson).
"In our recent paper, we prove this common lore wrong and show that thermal freeze-out is possible even when dark matter is several orders of magnitude heavier than the Higgs mass, if there are a set of dark particles that scatter off the standard model particles with nearest-neighbor interactions," Eric Kuflik, the other researcher behind the study, said. "The relic abundance of the dark matter is then determined by stochastic interactions between the dark particles and the Standard Model particles."

The mechanism proposed by Kim and Kuflik describes a set of dark matter particles scattering with ordinary matter through nearest-neighbor interactions, which change between species. In other words, it suggests that the dark matter takes a 'random walk' among dark matter species, continuously changing its identity. Based on the framework introduced by the researchers, therefore, the abundance of dark matter is thermally determined in the early universe, enabling extremely heavy dark matter masses.
"We have shown that dark matter can be produced from the early universe thermal bath while being in thermal equilibrium, even for dark matter masses substantially heavier than conventional wisdom would allow," Kim explained. "Interestingly, the abundance of dark matter particles in our scenario depends only on the interaction strength of the dark particles with the Standard model particles."
The new framework developed by Kim and Kuflik could have important implications for studies investigating the cosmic microwave background, structure formation and cosmic rays. In addition, it could serve as a benchmark for heavy dark matter experimental searches, as it suggests that decays to ordinary matter particles in the late universe could leave interesting astrophysical and cosmological signatures, which researchers could look for when searching for dark matter.
"There are two promising directions we hope to pursue in our future work," Kim said. "First, our mechanism inevitably predicts dark matter particles decaying to Standard Model particles throughout the history of the universe. This could leave interesting astrophysical signatures, such as ultra-high energy cosmic rays and so on. The implications for cosmology are also interesting."
So far, Kim and Kuflik have described the basic idea of superheavy dark matter and provided a 'simple toy model' of it by parameterizing the interaction strength between dark particles and standard model particles. In their next studies, however, Kim and Kuflik plan to conduct a detailed study of particle physics theories that could realize their mechanism of superheavy thermal dark matter.
"Explicit realizations in particle physics will help to identify the full suite of experimental signals predicted by the mechanism, which will teach us the best means to either exclude or detect such dark matter," Kuflik added.




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Dark matter may be older than the big bang, study suggests



[b]More information:[/b] Hyungjin Kim et al. Superheavy Thermal Dark Matter, Physical Review Letters (2019). DOI: 10.1103/PhysRevLett.123.191801

Kim Griest et al. Unitarity limits on the mass and radius of dark-matter particles, Physical Review Letters (2002). DOI: 10.1103/PhysRevLett.64.615
[b]Journal information:[/b] Physical Review Letters



https://phys.org/news/2019-11-framework-...-dark.html



NOVEMBER 26, 2019 REPORT
More dark-matter-deficient dwarf galaxies found
by Bob Yirka , Phys.org
[Image: darkmatter.jpg]Credit: CC0 Public Domain
A team of researchers with members affiliated with multiple institutions in China has found evidence for more dark-matter-deficient dwarf galaxies. In their paper published in the journal Nature Astronomy, the group describes their study of dwarf galaxies and how they found some they expected to be dominated by dark matter were not.

As the researchers note, standard cosmological theory suggests that dark matter drives formation of galaxies and the gravity wells in which they form. They note also that dwarf galaxies in the Local Group (those in our part of the universe) are dominated by dark matter. But just two years ago, two dwarf galaxies were observed that appeared to have less dark matter than was expected. Soon thereafter, two more were observed by another team. Now, in this new effort, the researchers have identified 19 dwarf galaxies with amounts of dark matter that do not conform to theory.
The work involved analyzing data from the Arecibo radio telescope to calculate galactic weights—this, the researchers note, can be done by measuring how fast hydrogen moves around them. The higher the speed, the more mass a galaxy has. They next added the mass of the hydrogen and all the of stars (using starlight data) to come up with a total non-dark matter mass for the galaxy. The difference between this number and the total mass was attributable to dark matter. In "normal" cases, just 2 percent of the mass of a dwarf galaxy is made up of non-dark matter. But in their study, they found what they describe as oddballs—one galaxy, for example, weighed in at approximately 14 billion suns, and its total non-dark matter mass made up approximately 27 percent of its total mass.
The researchers report that they analyzed 324 dwarf galaxies and found 19 that had less dark matter than theory has suggested they should. They suggest the "missing" dark matter might be attributed to neighbors pulling it off and keeping it to themselves—but some of the exceptions they found had no neighbors that were near enough to be considered suspects. They further suggest their findings could challenge formation theory as it applies to dwarf galaxies.




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The Milky Way kidnapped several tiny galaxies from its neighbor



[b]More information:[/b] Qi Guo et al. Further evidence for a population of dark-matter-deficient dwarf galaxies, Nature Astronomy (2019). DOI: 10.1038/s41550-019-0930-9
[b]Journal information:[/b] Nature Astronomy

https://phys.org/news/2019-11-dark-matte...axies.html
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RE: The Dark(S)Eye'd: GEODEs or a Singularity of The Darkside.  Arrow

JANUARY 6, 2020
New evidence shows that the key assumption made in the discovery of dark energy is in error
by Yonsei University
[Image: newevidences.jpg]Figure 1. Luminosity evolution mimicking dark energy in supernova (SN) cosmology. The Hubble residual is the difference in SN luminosity with respect to the cosmological model without dark energy (the black dotted line). The cyan circles are the binned SN data from Betoule et al. (2014). The red line is the evolution curve based on our age dating of early-type host galaxies. The comparison of our evolution curve with SN data shows that the luminosity evolution can mimic Hubble residuals used in the discovery and inference of the dark energy (the black solid line). Credit: Yonsei University
The most direct and strongest evidence for the accelerating universe with dark energy is provided by the distance measurements using type Ia supernovae (SN Ia) for the galaxies at high redshift. This result is based on the assumption that the corrected luminosity of SN Ia through the empirical standardization would not evolve with redshift.

New observations and analysis made by a team of astronomers at Yonsei University (Seoul, South Korea), together with their collaborators at Lyon University and KASI, show, however, that this key assumption is most likely in error. The team has performed very high-quality (signal-to-noise ratio ~175) spectroscopic observations to cover most of the reported nearby early-type host galaxies of SN Ia, from which they obtained the most direct and reliable measurements of population ages for these host galaxies. They find a significant correlation between SN luminosity and stellar population age at a 99.5 percent confidence level. As such, this is the most direct and stringent test ever made for the luminosity evolution of SN Ia. Since SN progenitors in host galaxies are getting younger with redshift (look-back time), this result inevitably indicates a serious systematic bias with redshift in SN cosmology. Taken at face values, the luminosity evolution of SN is significant enough to question the very existence of dark energy. When the luminosity evolution of SN is properly taken into account, the team found that the evidence for the existence of dark energy simply goes away (see Figure 1).
Commenting on the result, Prof. Young-Wook Lee (Yonsei Univ., Seoul), who led the project said, "Quoting Carl Sagan, extraordinary claims require extraordinary evidence, but I am not sure we have such extraordinary evidence for dark energy. Our result illustrates that dark energy from SN cosmology, which led to the 2011 Nobel Prize in Physics, might be an artifact of a fragile and false assumption."
Other cosmological probes, such as the cosmic microwave background (CMB) and baryonic acoustic oscillations (BAO), are also known to provide some indirect and "circumstantial" evidence for dark energy, but it was recently suggested that CMB from Planck mission no longer supports the concordance cosmological model which may require new physics (Di Valentino, Melchiorri, & Silk 2019). Some investigators have also shown that BAO and other low-redshift cosmological probes can be consistent with a non-accelerating universe without dark energy (see, for example, Tutusaus et al. 2017). In this respect, the present result showing the luminosity evolution mimicking dark energy in SN cosmology is crucial and very timely.
This result is reminiscent of the famous Tinsley-Sandage debate in the 1970s on luminosity evolution in observational cosmology, which led to the termination of the Sandage project originally designed to determine the fate of the universe.
This work based on the team's 9-year effort at Las Campanas Observatory 2.5-m telescope and at MMT 6.5-m telescope was presented at the 235th meeting of the American Astronomical Society held in Honolulu on January 5th (2:50 PM in cosmology session, presentation No. 153.05). Their paper is also accepted for publication in the Astrophysical Journal and will be published in January 2020 issue.




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Evidence for anisotropy of cosmic acceleration



[b]More information:[/b] Early-Type Host Galaxies of Type Ia Supernovae. II. Evidence for Luminosity Evolution in Supernova Cosmology, Astrophysical Journal arxiv.org/abs/1912.04903
[b]Journal information:[/b] Astrophysical Journal [/url]

Provided by Yonsei University


[url=https://phys.org/news/2020-01-evidence-key-assumption-discovery-dark.html]https://phys.org/news/2020-01-evidence-key-assumption-discovery-dark.html





Astrophysics > Astrophysics of Galaxies

Early-type Host Galaxies of Type Ia Supernovae. II. Evidence for Luminosity Evolution in Supernova Cosmology
Yijung KangYoung-Wook LeeYoung-Lo KimChul ChungChang Hee Ree
(Submitted on 10 Dec 2019)


Quote:The most direct and strongest evidence for the presence of dark energy is provided by the measurement of galaxy distances using type Ia supernovae (SNe Ia). This result is based on the assumption that the corrected brightness of SN Ia through the empirical standardization would not evolve with look-back time. Recent studies have shown, however, that the standardized brightness of SN Ia is correlated with host morphology, host mass, and local star formation rate, suggesting a possible correlation with stellar population property. In order to understand the origin of these correlations, we have continued our spectroscopic observations to cover most of the reported nearby early-type host galaxies. From high-quality (signal-to-noise ratio ~175) spectra, we obtained the most direct and reliable estimates of population age and metallicity for these host galaxies. We find a significant correlation between SN luminosity (after the standardization) and stellar population age at a 99.5% confidence level. As such, this is the most direct and stringent test ever made for the luminosity evolution of SN Ia. Based on this result, we further show that the previously reported correlations with host morphology, host mass, and local star formation rate are most likely originated from the difference in population age. This indicates that the light-curve fitters used by the SNe Ia community are not quite capable of correcting for the population age effect, which would inevitably cause a serious systematic bias with look-back time. Notably, taken at face values, a significant fraction of the Hubble residual used in the discovery of the dark energy appears to be affected by the luminosity evolution. We argue, therefore, that this systematic bias must be considered in detail in SN cosmology before proceeding to the details of the dark energy.
Comments:
Accepted for publication in ApJ; see Figure 16 for the luminosity evolution mimicking dark energy
Subjects:
Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
Cite as:
arXiv:1912.04903 [astro-ph.GA]
 
(or arXiv:1912.04903v1 [astro-ph.GA] for this version)


https://arxiv.org/abs/1912.04903







JANUARY 6, 2020

Astronomers detect first stars 'bubbling out' from the cosmic Dark Ages

by Peter Michaud, National Science Foundation
[Image: astronomersd.jpg]This rendition shows ionized bubbles formed by three galaxies in galaxy cluster EGS77. Credit: V. Tilvi et al./National Science Foundation’s Optical-Infrared Astronomy Research Laboratory/KPNO/AURA
Astronomers using the Mayall telescope at Kitt Peak National Observatory, a program of NSF's National Optical-Infrared Astronomy Research Laboratory, have identified several overlapping bubbles of hydrogen gas ionized by the stars in early galaxies, a mere 680 million years after the Big Bang. This is the earliest direct evidence from the period when the first generation of stars formed and began reionizing the hydrogen gas that permeated the universe.

There was a period in the very early universe—known as the "cosmic dark ages"—when elementary particles, formed in the Big Bang, had combined to form neutral hydrogen but no stars or galaxies existed yet to light up the universe. This period began less than half a million years after the Big Bang and ended with the formation of the first stars. While this stage in the evolution of our universe is indicated by computer simulations, direct evidence is sparse.
Now, astronomers using the infrared imager NEWFIRM on the 4-meter Mayall Telescope at the Kitt Peak National Observatory of NSF's National Optical-Infrared Astronomy Research Laboratory (OIR Lab), have reported imaging a group of galaxies, known as EGS77, that contains these first stars. EGS, or the Extended Groth Strip, is a region imaged by HST in 2005; it corresponds to a narrow strip of the sky about the width of a finger held at arms length. There are at least 50,000 galaxies known within the strip. Their results were announced at a press conference held today at the 235th meeting of the American Astronomical Society (AAS) in Honolulu, Hawai'i.
"The young universe was filled with hydrogen atoms, which so attenuate ultraviolet light that they block our view of early galaxies," said James Rhoads at NASA's Goddard Space Flight Center in Greenbelt, Maryland, who presented the findings at the AAS press conference. "EGS77 is the first galaxy group caught in the act of clearing out this cosmic fog."
The team began with an imaging survey designed to detect high redshift galaxies and combined these data with corresponding images taken by the Hubble Space Telescope. This enabled the team to compute what is known as a photometric redshift, a proxy for estimating distance. At these redshifts, a galaxy's light is shifted completely out of the range of wavelengths to which the human eye is sensitive (the visible spectrum) to longer (infrared) wavelengths. The criteria for selecting distant galaxy candidates included a clear detection of them in the special infrared narrowband filters used with NEWFIRM on the Mayall 4-meter telescope and a complete non-detection in the shorter wavelength optical filter bands used by Hubble. "The discovery of the two fainter galaxies in the group was only possible because of the special narrowband filter used with NEWFIRM," said team leader Vithal Tilvi, a researcher at Arizona State University in Tempe.

"Intense light from galaxies can ionize the surrounding hydrogen gas, forming bubbles that allow starlight to travel freely," said Tilvi. "EGS77 has formed a large bubble that allows its light to travel to Earth without much attenuation. Eventually, bubbles like these grew around all galaxies and filled intergalactic space, clearing the way for light to travel across the universe."
EGS77 was discovered as part of the Cosmic Deep And Wide Narrowband (Cosmic DAWN) survey, for which Rhoads serves as principal investigator. The team imaged a small area in the constellation of Boötes using a custom-built filter on the National Optical Astronomy Observatory's Extremely Wide-Field InfraRed imager (NEWFIRM). Ron Probst, a DAWN team member who also helped to develop NEWFIRM, adds, "These results show the value of maintaining instruments at our national observatories that are powerful and can flexibly adapt to pursue new scientific questions, questions that may not have been in mind when an instrument was originally built."
Once identified, the distances and hence the ages of these galaxies were confirmed with spectra taken with the MOSFIRE spectrograph at the Keck I telescope at the W. M. Keck Observatory on Maunakea in Hawai'i. All three galaxies show strong emission lines of hydrogen Lyman alpha at a redshift (z = 7.7), which means we are seeing them at about 680 million years after the Big Bang. The size of the ionized bubble around each was derived from computer modeling. These bubbles overlap spatially, but are large enough (about 2.2 million light-years) that Lyman alpha photons are redshifted before they reach the boundary of the bubble and can thus escape unscathed, allowing astronomers to detect them.
"We expected that reionization bubbles from this era in cosmic history would be rare and hard to find," said Sangeeta Malhotra, a collaborator at NASA GSFC, "so confirmation of this transition is important." This "cosmic dawn," the intermediate state between a neutral and an ionized universe, is something that has been predicted. Such discoveries are made possible by the availability of powerful astronomical instruments that can probe the universe in a way unimagined by past generations of astronomers.
This research will be presented in a forthcoming paper and is currently close to acceptance.




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'Green peas' provide clues to the early days of the universe



Provided by National Science Foundation

https://phys.org/news/2020-01-astronomer...-ages.html




JANUARY 6, 2020

Astronomers spot distant galaxy group driving ancient cosmic makeover

by Francis Reddy, NASA
[Image: astronomerss.gif]This composite of archival Hubble Space Telescope visible and near-infrared images shows a part of the Extended Groth Strip, a well-studied area located between the constellations Ursa Major and Boötes. The three galaxies of the EGS77 galaxy group, shown in the green circles, lie at a redshift of 7.7, which means we’re seeing the galaxies as they were when the universe was just 680 million years old. The image is 3.2 arcminutes across. Credit: NASA, ESA and V. Tilvi (ASU)
An international team of astronomers funded in part by NASA has found the farthest galaxy group identified to date. Called EGS77, the trio of galaxies dates to a time when the universe was only 680 million years old, or less than 5% of its current age of 13.8 billion years.

More significantly, observations show the galaxies are participants in a sweeping cosmic makeover called reionization. The era began when light from the first stars changed the nature of hydrogen throughout the universe in a manner akin to a frozen lake melting in the spring. This transformed the dark, light-quenching early cosmos into the one we see around us today.
"The young universe was filled with hydrogen atoms, which so attenuate ultraviolet light that they block our view of early galaxies," said James Rhoads at NASA's Goddard Space Flight Center in Greenbelt, Maryland, who presented the findings on Jan. 5 at the 235th meeting of the American Astronomical Society in Honolulu. "EGS77 is the first galaxy group caught in the act of clearing out this cosmic fog."
While more distant individual galaxies have been observed, EGS77 is the farthest galaxy group to date showing the specific wavelengths of far-ultraviolet light revealed by reionization. This emission, called Lyman alpha light, is prominent in all members of EGS77.

This animation shows EGS77’s place in cosmic history, flies to the galaxies, and illustrates how ultraviolet light from their stars create bubbles of ionized hydrogen around them. Credit: NASA’s Goddard Space Flight Center
In its earliest phase, the universe was a glowing plasma of particles, including electrons, protons, atomic nuclei, and light. Atoms could not yet exist. The universe was in an ionized state, similar to the gas inside a lighted neon sign or fluorescent tube.
After the universe expanded and cooled for about 380,000 years, electrons and protons combined into the first atoms—more than 90% of them hydrogen. Hundreds of millions of years later, this gas formed the first stars and galaxies. But the very presence of this abundant gas poses challenges for spotting galaxies in the early universe.
Hydrogen atoms readily absorb and quickly re-emit far-ultraviolet light known as Lyman alpha emission, which has a wavelength of 121.6 nanometers. When the first stars formed, some of the light they produced matched this wavelength. Because Lyman alpha light easily interacted with hydrogen atoms, it couldn't travel far before the gas scattered it in random directions.

"Intense light from galaxies can ionize the surrounding hydrogen gas, forming bubbles that allow starlight to travel freely," said team member Vithal Tilvi, a researcher at Arizona State University in Tempe. "EGS77 has formed a large bubble that allows its light to travel to Earth without much attenuation. Eventually, bubbles like these grew around all galaxies and filled intergalactic space, reionizing the universe and clearing the way for light to travel across the cosmos."

This visualization shows how ultraviolet light from the first stars and galaxies gradually transformed the universe. Hydrogen atoms, also called neutral hydrogen, readily scatters UV light, preventing it from traveling very far from its sources. Gradually, intense UV light from stars and galaxies split apart the hydrogen atoms, creating expanding bubbles of ionized gas. As these bubbles grew and overlapped, the cosmic fog lifted. Astronomers call this process reionization. Here, regions already ionized are blue and translucent, areas undergoing ionization are red and white, and regions of neutral gas are dark and opaque. Credit: M. Alvarez, R. Kaehler and T. Abel (2009)
EGS77 was discovered as part of the Cosmic Deep And Wide Narrowband (Cosmic DAWN) survey, for which Rhoads serves as principal investigator. The team imaged a small area in the constellation Boötes using a custom-built filter on the National Optical Astronomy Observatory's Extremely Wide-Field InfraRed Imager (NEWFIRM), which was attached to the 4-meter Mayall telescope at Kitt Peak National Observatory near Tucson, Arizona.
Because the universe is expanding, Lyman alpha light from EGS77 has been stretched out during its travels, so astronomers actually detect it at near-infrared wavelengths. We can't see these galaxies in visible light now because that light started out at shorter wavelengths than Lyman alpha and was scattered by the fog of hydrogen atoms.
To help select distant candidates, the researchers compared their images with publicly available data of the same region taken by NASA's Hubble and Spitzer space telescopes. Galaxies appearing brightly in near-infrared images were tagged as possibilities, while those appearing in visible light were rejected as being too close.
The team confirmed the distances to EGS77's galaxies by using the Multi-Object Spectrometer for Infra-Red Exploration (MOSFIRE) on the Keck I telescope at the W. M. Keck Observatory on Maunakea, Hawaii. The three galaxies all show Lyman alpha emission lines at slightly different wavelengths, reflecting slightly different distances. The separation between adjacent galaxies is about 2.3 million light-years, or slightly closer than the distance between the Andromeda galaxy and our own Milky Way.

[Image: astronomerss.jpg]
Inset: This illustration of the EGS77 galaxy group shows the galaxies surrounded by overlapping bubbles of ionized hydrogen. By transforming light-quenching hydrogen atoms to ionized gas, ultraviolet starlight is thought to have formed such bubbles throughout the early universe, gradually transitioning it from opaque to completely transparent. Background: This composite of archival Hubble Space Telescope visible and near-infrared images includes the three galaxies of EGS77 (green circles). Credit: NASA, ESA and V. Tilvi (ASU)
A paper describing the findings, led by Tilvi, has been submitted to The Astrophysical Journal.
"While this is the first galaxy group identified as being responsible for cosmic reionization, future NASA missions will tell us much more," said co-author Sangeeta Malhotra at Goddard. "The upcoming James Webb Space Telescope is sensitive to Lyman alpha emission from even fainter galaxies at these distances and may find more galaxies within EGS77."
Astronomers expect that similar reionization bubbles from this era will be rare and hard to find. NASA's planned Wide Field Infrared Survey Telescope (WFIRST) may be able to uncover additional examples, further illuminating this important transition in cosmic history.




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Astronomers detect first stars 'bubbling out' from the cosmic Dark Ages



https://phys.org/news/2020-01-astronomer...cient.html
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MARCH 31, 2020
Hubble finds best evidence for elusive mid-sized black hole
[Image: hubblefindsb.jpg]This illustration depicts a cosmic homicide in action. A wayward star is being shredded by the intense gravitational pull of a black hole that contains tens of thousands of solar masses. The stellar remains are forming an accretion disk around the black hole. Flares of X-ray light from the super-heated gas disk alerted astronomers to the black hole's location; otherwise it lurked unknown in the dark. The elusive object is classified as an intermediate mass black hole (IMBH), as it is much less massive than the monster black holes that dwell in the centers of galaxies. Therefore, IMBHs are mostly quiescent because they do not pull in as much material, and are hard to find. Hubble observations provide evidence that the IMBH dwells inside a dense star cluster. The cluster itself may be the stripped-down core of a dwarf galaxy. Credit: NASA, ESA and D. Player (STScI)
Astronomers have found the best evidence for the perpetrator of a cosmic homicide: a black hole of an elusive class known as "intermediate-mass," which betrayed its existence by tearing apart a wayward star that passed too close.

Weighing in at about 50,000 times the mass of our Sun, the black hole is smaller than the supermassive black holes (at millions or billions of solar masses) that lie at the cores of large galaxies, but larger than stellar-mass black holes formed by the collapse of a massive star.
These so-called intermediate-mass black holes (IMBHs) are a long-sought "missing link" in black hole evolution. Though there have been a few other IMBH candidates, researchers consider these new observations the strongest evidence yet for mid-sized black holes in the universe.
It took the combined power of two X-ray observatories and the keen vision of NASA's Hubble Space Telescope to nail down the cosmic beast.
"Intermediate-mass black holes are very elusive objects, and so it is critical to carefully consider and rule out alternative explanations for each candidate. That is what Hubble has allowed us to do for our candidate," said Dacheng Lin of the University of New Hampshire, principal investigator of the study. The results are published on March 31, 2020, in The Astrophysical Journal Letters.

Astronomers have found the best evidence for a black hole of an elusive class known as "intermediate-mass," which betrayed its existence by tearing apart a wayward star that passed too close. This exciting discovery opens the door to the possibility of many more lurking undetected in the dark, waiting to be given away by a star passing too close. Credit: NASA's Goddard Space Flight Center
The story of the discovery reads like a Sherlock Holmes story, involving the meticulous step-by-step case-building necessary to catch the culprit.
Lin and his team used Hubble to follow up on leads from NASA's Chandra X-ray Observatory and ESA's (the European Space Agency) X-ray Multi-Mirror Mission (XMM-Newton). In 2006 these satellites detected a powerful flare of X-rays, but they could not determine whether it originated from inside or outside of our galaxy. Researchers attributed it to a star being torn apart after coming too close to a gravitationally powerful compact object, like a black hole.
Surprisingly, the X-ray source, named 3XMM J215022.4?055108, was not located in a galaxy's center, where massive black holes normally would reside. This raised hopes that an IMBH was the culprit, but first another possible source of the X-ray flare had to be ruled out: a neutron star in our own Milky Way galaxy, cooling off after being heated to a very high temperature. Neutron stars are the crushed remnants of an exploded star.

Hubble was pointed at the X-ray source to resolve its precise location. Deep, high-resolution imaging provides strong evidence that the X-rays emanated not from an isolated source in our galaxy, but instead in a distant, dense star cluster on the outskirts of another galaxy—just the type of place astronomers expected to find an IMBH. Previous Hubble research has shown that the mass of a black hole in the center of a galaxy is proportional to that host galaxy's central bulge. In other words, the more massive the galaxy, the more massive its black hole. Therefore, the star cluster that is home to 3XMM J215022.4?055108 may be the stripped-down core of a lower-mass dwarf galaxy that has been gravitationally and tidally disrupted by its close interactions with its current larger galaxy host.

[Image: 1-hubblefindsb.jpg]
This Hubble Space Telescope image identified the location of an intermediate-mass black hole, weighing 50,000 times the mass of our Sun (making it much smaller than supermassive black holes found in the centers of galaxies). The black hole, named 3XMM J215022.4?055108, is indicated by the white circle. The elusive type of black hole was first identified in a burst of telltale X-rays emitted by hot gas from a star as it was captured and destroyed by the black hole. Hubble was needed to pinpoint the black hole's location in visible light. Hubble's deep, high-resolution imaging shows that the black hole resides inside a dense cluster of stars that is far beyond our Milky Way galaxy. The star cluster is in the vicinity of the galaxy at the center of the image. Much smaller-looking background galaxies appear sprinkled around the image, including a face-on spiral just above the central foreground galaxy. This photo was taken with Hubble's Advanced Camera for Surveys. Credit: NASA, ESA and D. Lin (University of New Hampshire)
IMBHs have been particularly difficult to find because they are smaller and less active than supermassive black holes; they do not have readily available sources of fuel, nor as strong a gravitational pull to draw stars and other cosmic material which would produce telltale X-ray glows. Astronomers essentially have to catch an IMBH red-handed in the act of gobbling up a star. Lin and his colleagues combed through the XMM-Newton data archive, searching hundreds of thousands of observations to find one IMBH candidate.
The X-ray glow from the shredded star allowed astronomers to estimate the black hole's mass of 50,000 solar masses. The mass of the IMBH was estimated based on both X-ray luminosity and the spectral shape. "This is much more reliable than using X-ray luminosity alone as typically done before for previous IMBH candidates," said Lin. "The reason why we can use the spectral fits to estimate the IMBH mass for our object is that its spectral evolution showed that it has been in the thermal spectral state, a state commonly seen and well understood in accreting stellar-mass black holes."

[Image: 2-hubblefindsb.jpg]
This artist's impression depicts a star being torn apart by an intermediate-mass black hole (IMBH), surrounded by an accretion disc. This thin, rotating disc of material consists of the leftovers of a star which was ripped apart by the tidal forces of the black hole. Credit: ESA/Hubble, M. Kornmesser
This object isn't the first to be considered a likely candidate for an intermediate-mass black hole. In 2009 Hubble teamed up with NASA's Swift observatory and ESA's XMM-Newton to identify what is interpreted as an IMBH, called HLX-1, located towards the edge of the galaxy ESO 243-49. It too is in the center of a young, massive cluster of blue stars that may be a stripped-down dwarf galaxy core. The X-rays come from a hot accretion disk around the black hole. "The main difference is that our object is tearing a star apart, providing strong evidence that it is a massive black hole, instead of a stellar-mass black hole as people often worry about for previous candidates including HLX-1," Lin said.
Finding this IMBH opens the door to the possibility of many more lurking undetected in the dark, waiting to be given away by a star passing too close. Lin plans to continue his meticulous detective work, using the methods his team has proved successful. Many questions remain to be answered. Does a supermassive black hole grow from an IMBH? How do IMBHs themselves form? Are dense star clusters their favored home?




Explore further
Galaxy NGC 3319 may host an active intermediate-mass black hole, study finds



[b]Journal information:[/b] Astrophysical Journal Letters [/url]

Provided by 
NASA's Goddard Space Flight Center

https://phys.org/news/2020-03-hubble-evi...black.html






MARCH 31, 2020
New method predicts which black holes escape their galaxies
by Linda B. Glaser, Cornell University
[Image: newmethodpre.jpg]Credit: NASA
Shoot a rifle, and the recoil might knock you backward. Merge two black holes in a binary system, and the loss of momentum gives a similar recoil—a "kick"—to the merged black hole.

"For some binaries, the kick can reach up to 5000 kilometers a second, which is larger than the escape velocity of most galaxies," said Vijay Varma, an astrophysicist at the California Institute of Technology and an incoming inaugural Klarman Fellow at Cornell University's College of Arts & Sciences.
Varma and his fellow researchers have developed a new method using gravitational wave measurements to predict when a final black hole will remain in its host galaxy and when it will be ejected. Such measurements could provide a crucial missing piece of the puzzle behind the origin of heavy black holes, said Varma, as well as offer insights into galaxy evolution and tests of general relativity. He is lead author of "Extracting the Gravitational Recoil from Black Hole Merger Signals," published March 13 in Physical Review Letters and co-authored with Maximiliano Isi and Sylvia Biscoveanu of the Massachusetts Institute of Technology.
As black holes orbit in a binary system, their gravitational waves carry away energy and angular momentum, which causes the binary system to shrink as it spirals inward. When a system has asymmetries, such as unequal masses, gravitational waves aren't emitted equally in all directions, which causes a net loss of linear momentum, resulting in a recoil. Most of that recoil happens right near the merger which can result in a kick great enough to extract the newly merged black hole from its host galaxy.

This simulation shows the merger of a 35 solar-mass black hole with a 25 solar-mass black hole, followed by the recoil (kick) of the final black hole. The movie is sped-up after the merger to highlight the kick. The arrows indicate the spins (rotation) of the black holes—these interact with the orbital angular momentum (pink arrow), causing the orbital plane to wobble as the binary evolves. The blue and red orbs indicate patterns of gravitational waves generated in the collision. Credit: Vijay Varma
The researchers' models are based on supercomputer simulations that numerically solve Einstein's equations of general relativity. The simulations were performed as part of a larger research effort under the Simulating eXtreme Spacetimes (SXS) Collaboration that includes research groups from Caltech and Cornell. Saul Teukolsky, Cornell's Hans A. Bethe Professor of Physics, serves as the group leader.
"This research shows how gravitational wave signals can be used to learn about astrophysical phenomena in an unexpected way," said Teukolsky. "It had been believed that we would have to wait more than a decade for detectors sensitive enough to do this kind of work, but this research shows we can in fact do it now—very exciting!"
While the existing publicly available gravitational wave signals announced by LIGO and Virgo were not strong enough for a good recoil measurement, according to the authors as these detectors improve over the next few years this method will be able to reliably measure the kick.




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Researchers find gravitational wave candidates from binary black hole mergers in public LIGO/Virgo data



[b]More information:[/b] Vijay Varma et al. Extracting the Gravitational Recoil from Black Hole Merger Signals, Physical Review Letters (2020). DOI: 10.1103/PhysRevLett.124.101104

Simulation of black hole merger - vijayvarma392.github.io/binaryBHexp/
[b]Journal information:[/b] Physical Review Letters 

Provided by [url=https://phys.org/partners/cornell-university/]Cornell University

https://phys.org/news/2020-03-method-bla...axies.html
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#13
APRIL 8, 2020
Black hole bends light back on itself
by Whitney Clavin
[Image: blackholeben.jpg]This illustration shows how some of the light coming from a disk around a black hole is bent back onto the disk itself due to the gravity of the monstrous black hole. The light is then reflected back off the disk. Astronomers using data from NASA's now-defunct Rossi X-ray Timing Explorer (RXTE) mission were able to distinguish between light that came straight from the disk and light that was reflected. The bluish material coming off the black hole is an outflowing jet of energetic particles. Credit: NASA/JPL-Caltech/R. Hurt (IPAC)/R. Connors (Caltech)
You may have heard that nothing escapes the gravitational grasp of a black hole, not even light. This is true in the immediate vicinity of a black hole, but a bit farther out—in disks of material that swirl around some black holes—light can escape. In fact, this is the reason actively growing black holes shine with brilliant X-rays.

Now, a new study accepted for publication in The Astrophysical Journal offers evidence that, in fact, not all of the light streaming from a black hole's surrounding disk easily escapes. Some of it gives in to the monstrous pull of the black hole, turns back, and then ultimately bounces off the disk and escapes.
"We observed light coming from very close to the black hole that is trying to escape, but instead is pulled right back by the black hole like a boomerang," says Riley Connors, lead author of the new study and a postdoctoral scholar at Caltech. "This is something that was predicted in the 1970s, but hadn't been shown until now."
The new findings were made possible by combing through archival observations from NASA's now-defunct Rossi X-ray Timing Explorer (RXTE) mission, which came to an end in 2012. The researchers specifically looked at a black hole that is orbited by a sun-like star; together, the pair is called XTE J1550-564. The black hole "feeds" off this star, pulling material onto a flat structure around it called an accretion disk. By looking closely at the X-ray light coming from the disk as the light spirals toward the black hole, the team found imprints indicating that the light had been bent back toward the disk and reflected off.
"The disk is essentially illuminating itself," says co-author Javier Garcia, a research assistant professor of physics at Caltech. "Theorists had predicted what fraction of the light would bend back on the disk, and now, for the first time, we have confirmed those predictions."
The scientists say that the new results offer another indirect confirmation of Albert Einstein's general theory of relativity, and also will help in future measurements of the spin rates of black holes, something that is still poorly understood.
"Since black holes can potentially spin very fast, they not only bend the light but twist it," says Connors. "These recent observations are another piece in the puzzle of trying to figure out how fast black holes spin."
The new study is titled "Evidence for Returning Disk Radiation in the Black Hole X-ray Binary XTEJ1550-564."




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Shedding light on black holes



[b]More information:[/b] Riley M. T. Connors et al. Evidence for Returning Disk Radiation in the Black Hole X-Ray Binary XTE J1550–564, The Astrophysical Journal (2020). DOI: 10.3847/1538-4357/ab7afc
[b]Journal information:[/b] Astrophysical Journal
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#14
circular illogic.

Quote:"If an electron is at the center of the donut, it cannot escape from it: it is trapped in the light beam," 

black holes fulla whatzamatta -u trap light and light can trap matter at itz center 


APRIL 8, 2020 FEATURE
First successful laser trapping of circular Rydberg atoms
by Ingrid Fadelli , Phys.org
[Image: firstsuccess.jpg]An artistic picture of laser-trapped circular Rydberg atoms. Credit: Clément Sayrin, LKB.
Rydberg atoms, which are atoms in a highly excited state, have several unique and advantageous properties, including a particularly long lifetime and large sensitivities to external fields. These properties make them valuable for a variety of applications, for instance for the development of quantum technologies.

In order for Rydberg atoms to be effectively used in quantum technology, however, researchers first need to be able to trap them. While a number of studies have demonstrated the trapping of Rydberg atoms using magnetic, electric, or laser technology, the trapping times achieved so far have been relatively short, typically around 100μs.
Researchers at Laboratoire Kastler Brossel (LKB) have recently achieved a longer 2-D laser trapping time of circular Rydberg atoms of up to 10 ms. The method they employed, outlined in a paper published in Physical Review Letters, could open up exciting new possibilities for the development of quantum technology.
"Our research group at LKB is one of the few worldwide that can prepare and manipulate circular Rydberg levels of atoms," Clément Sayrin, one of the researchers who carried out the study, told Phys.org. "Our group has actually a long experience in working with circular Rydberg atoms, which roots back to the 1970s/1980s and the work of Serge Haroche. A significant part of our research activities is now devoted to the use of these atoms in quantum technologies."
Most quantum simulators employing Rydberg atoms developed to date use non-circular Rydberg atoms. These technologies were first pioneered by a research group at Institut d'Optique Graduate School (IOGS) in Palaiseau, led by Antoine Browaeys and Thierry Lahaye, as well as by a team at Harvard led by Mikhail Lukin.
While these simulators have achieved remarkable results, their capabilities have been limited by the fact that the Rydberg atoms inside them were not trapped and thus continued to move as the system operated. The new study conducted by Sayrin, Michel Brune (director of research), Rodrigo Cortiñas (Ph.D. student), Maxime Favier (post-doctoral student) and other researchers at LKB introduces a solution to this problem that entails the use of circular Rydberg atoms (i.e., atoms in Rydberg circular states) and a technique known as laser trapping.

"When an atom is excited to a circular Rydberg level, it can be fairly described as an electron that orbits far from the nucleus on a circular orbit, an orbit almost as large as a bacterium," Sayrin explained. "Hence, the electron is almost free and free electrons, as any charged particle, are repelled by intense light fields."
The researchers essentially leveraged the fact that circular Rydberg atoms are repelled by intense light to trap the atoms. To achieve this, they produced a donut-shaped light beam, more specifically a round laser beam with a dark spot at its center, where the atoms would ultimately be trapped.
"If an electron is at the center of the donut, it cannot escape from it: it is trapped in the light beam," Sayrin explained. "The heavy nucleus then just follows, attracted by the electron via the Coulomb interaction! Somehow, we trap the circular Rydberg atom by grabbing it by its electron."
Sayrin and his colleagues produced the donut-shaped beam using a tool known as a spatial light modulator (SLM). SLMs are objects that can imprint phase patterns on light beams, which in turn modifies the shape of these beams. These unique tools were once widely used in video projectors to reflect images or videos onto surfaces.
"Somehow, we have made our own video projector to produce the donut beam, but instead of a light bulb as source, we have a powerful infrared laser, and instead of a screen we shine the image on the Rydberg atoms," Sayrin said.
So far, researchers worldwide have only been able to demonstrate early signatures of the laser trapping of non-circular atoms, which lasted no more than a few microseconds. Circular Rydberg atoms, on the other hand, had never been laser trapped before.
The recent study by Sayrin and his colleagues shows that circular Rydberg atoms can, in fact, be laser trapped and for remarkably longer timescales. So far, the researchers were able to trap these atoms for approximately 10 milliseconds, yet this trapping time could be increased further in future studies.
"We have also showed that trapping the circular Rydberg atoms does not affect their properties (e.g., lifetime, purity, and quantum coherence)," Sayrin said. "In particular, it confirms the fact that circular Rydberg atoms are immune to photo-ionization, contrarily to other Rydberg levels."
The results could have numerous important implications for the development of quantum technologies, including tools for quantum simulation, sensing, and information processing. In fact, effectively keeping circular Rydberg atoms in place while quantum systems are operating, as demonstrated in their study, means that these atoms could be used for longer times. This may ultimately boost the performance of different quantum technologies, for instance enhancing the sensitivity of sensors, increasing the simulation time of simulators, and so on.
Sayrin and his colleagues are now planning to realize an array of laser-trapped circular Rydberg atoms. To achieve this, they will prepare an array of optical tweezers with a hole in its center, a structure known as 'bottle beam trap."
"By trapping one and only one circular Rydberg atom in every bottle, separated by a few microns, we will produce a regular array of interacting circular Rydberg atoms," Sayrin explained. "This will realize a quantum simulator of interacting spins that should allow us to run simulations over unprecedented time scales."




Explore further
3-D trapping of Rydberg atoms in holographic optical bottle beam traps



[b]More information:[/b] R. G. Cortiñas et al. Laser Trapping of Circular Rydberg Atoms, Physical Review Letters (2020). DOI: 10.1103/PhysRevLett.124.123201
[b]Journal information:[/b] Physical Review Letters 

   




If atoms can be trapped by tiny donut shaped lasers what can be trapped from jets and flares from neutron stars quasars or blazars?  Assimilated
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#15
...
That is really interesting reading, and amazing science technology in it's infancy.


Quote:Somehow, we trap the circular Rydberg atom by grabbing it by its electron. 



for 10 milliseconds ... but nonetheless ... unexpectedly bizarre

Makes one wonder about advanced alien technological societies. 
Ones that survive self annihilation or planetary eco apocalypse,
with those technologies intact, 
and social infrastructures that still maintain personal rights and freedoms.
I see amazing technology like this one develop on Earth,
and temporarily have hope of the good science out pacing the bad science.
On Earth, all innovative discovery goes to military applications for first applications.
Then you wonder how this quantum information technology,
using "circular Rydberg atoms"
will be applied to brain implants linked to AI and such somehow.
 
The benign warm-n-fuzzy approach:
This Is Your Brain on Quantum Computers - Singularity Hub
https://singularityhub.com/2016/10/02/th...computers/



The not so warm-n-fuzzy reality:
The Government Is Serious About Creating Mind-Controlled Weapons
 https://www.livescience.com/65546-darpa-...apons.html


Quote:The group's plan,
relies on specially designed nanoparticles with magnetic cores,
and piezoelectric outer shells, 
which means the shells can convert mechanical energy to electrical and vice versa. 

The particles will be injected Whip  {nanometh}
or nasally administered Rofl  {the new cocaine}

and magnetic fields Herethere will guide them to specific  Hi neurons.


Let's trap some neurons and make them work for DARPA !



Quote:To do this, 
Robinson's team plans to use viruses  Naughty
modified to deliver genetic material into cells — called viral vectors — 

to insert DNA into specific  Hi neurons, 
that will make them produce two kinds of proteins.


The Neuron Trap -- get your home version of the game from DARPA



Quote:Somehow, we trap the circular Rydberg atom by grabbing it by its electron.


Holycowsmile



Quote:If atoms can be trapped by tiny donut shaped lasers,
what can be trapped from jets and flares,
from neutron stars quasars or blazars?


perhaps 
a planet with an orbiting moon ...
not far from the source ... trapped for 10 milliseconds ... in a halo CME ... 
perhaps
TIME . . . . . Whip  

perhaps
is always possible 

It is an interesting concept actually.
A bit rough, but heck, think BIG, why not?
I like it.

...
Reply
#16
Now you know.

  1. 3.
    PHYSICS
    formed by the intersection of reflected or refracted parallel rays from a curved surface.


noun
noun: caustic; plural noun: caustics



Gnostic caustic.

[Image: blackholeben.jpg]
...


[Image: 26459820962_9db0403650_c.jpg]
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#17
APRIL 16, 2020
Very Large Telescope sees star dance around supermassive black hole, proves Einstein right
by ESO
[Image: 2-esotelescope.jpg]Observations made with ESO's Very Large Telescope (VLT) have revealed for the first time that a star orbiting the supermassive black hole at the centre of the Milky Way moves just as predicted by Einstein's theory of general relativity. Its orbit is shaped like a rosette and not like an ellipse as predicted by Newton's theory of gravity. This effect, known as Schwarzschild precession, had never before been measured for a star around a supermassive black hole. This artist's impression illustrates the precession of the star's orbit, with the effect exaggerated for easier visualisation. Credit: ESO/L. Calçada
Observations made with ESO's Very Large Telescope (VLT) have revealed for the first time that a star orbiting the supermassive black hole at the centre of the Milky Way moves just as predicted by Einstein's general theory of relativity. Its orbit is shaped like a rosette and not like an ellipse as predicted by Newton's theory of gravity. This long-sought-after result was made possible by increasingly precise measurements over nearly 30 years, which have enabled scientists to unlock the mysteries of the behemoth lurking at the heart of our galaxy.

"Einstein's General Relativity predicts that bound orbits of one object around another are not closed, as in Newtonian Gravity, but precess forwards in the plane of motion. This famous effect—first seen in the orbit of the planet Mercury around the Sun—was the first evidence in favour of General Relativity. One hundred years later we have now detected the same effect in the motion of a star orbiting the compact radio source Sagittarius A* at the centre of the Milky Way. This observational breakthrough strengthens the evidence that Sagittarius A* must be a supermassive black hole of 4 million times the mass of the Sun," says Reinhard Genzel, Director at the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany and the architect of the 30-year-long programme that led to this result.
Located 26 000 light-years from the Sun, Sagittarius A* and the dense cluster of stars around it provide a unique laboratory for testing physics in an otherwise unexplored and extreme regime of gravity. One of these stars, S2, sweeps in towards the supermassive black hole to a closest distance less than 20 billion kilometres (one hundred and twenty times the distance between the Sun and Earth), making it one of the closest stars ever found in orbit around the massive giant. At its closest approach to the black hole, S2 is hurtling through space at almost three percent of the speed of light, completing an orbit once every 16 years. "After following the star in its orbit for over two and a half decades, our exquisite measurements robustly detect S2's Schwarzschild precession in its path around Sagittarius A*," says Stefan Gillessen of the MPE, who led the analysis of the measurements published today in the journal Astronomy & Astrophysics.

Most stars and planets have a non-circular orbit and therefore move closer to and further away from the object they are rotating around. S2's orbit precesses, meaning that the location of its closest point to the supermassive black hole changes with each turn, such that the next orbit is rotated with regard to the previous one, creating a rosette shape. General Relativity provides a precise prediction of how much its orbit changes and the latest measurements from this research exactly match the theory. This effect, known as Schwarzschild precession, had never before been measured for a star around a supermassive black hole.

The study with ESO's VLT also helps scientists learn more about the vicinity of the supermassive black hole at the centre of our galaxy. "Because the S2 measurements follow General Relativity so well, we can set stringent limits on how much invisible material, such as distributed dark matter or possible smaller black holes, is present around Sagittarius A*. This is of great interest for understanding the formation and evolution of supermassive black holes," say Guy Perrin and Karine Perraut, the French lead scientists of the project.
This result is the culmination of 27 years of observations of the S2 star using, for the best part of this time, a fleet of instruments at ESO's VLT, located in the Atacama Desert in Chile. The number of data points marking the star's position and velocity attests to the thoroughness and accuracy of the new research: the team made over 330 measurements in total, using the GRAVITY, SINFONI and NACO instruments. Because S2 takes years to orbit the supermassive black hole, it was crucial to follow the star for close to three decades, to unravel the intricacies of its orbital movement.


The research was conducted by an international team led by Frank Eisenhauer of the MPE with collaborators from France, Portugal, Germany and ESO. The team make up the GRAVITY collaboration, named after the instrument they developed for the VLT Interferometer, which combines the light of all four 8-metre VLT telescopes into a super-telescope (with a resolution equivalent to that of a telescope 130 metres in diameter). The same team reported in 2018 another effect predicted by General Relativity: they saw the light received from S2 being stretched to longer wavelengths as the star passed close to Sagittarius A*. "Our previous result has shown that the light emitted from the star experiences General Relativity. Now we have shown that the star itself senses the effects of General Relativity," says Paulo Garcia, a researcher at Portugal's Centre for Astrophysics and Gravitation and one of the lead scientists of the GRAVITY project.

[Image: verylargetel.jpg]
Left: The data points for the orbit of S2 around Sgr A* (black cross at (0,0)) were collected by different instruments with the VLT over 27 years. Even though the star orbit appears almost closed in this image, the small Schwarzschild precession is significantly detected and corresponds to the theoretical predictions of general relativity. This effect is greatly exaggerated in the artistic representation above. The figure on the right shows that the positions of the star (turquoise dots) agree with the theoretical predictions of general relativity (red line) within the measurement inaccuracy. The Newtonian prediction (blue dashed line) is clearly excluded. Credit: © MPE
With ESO's upcoming Extremely Large Telescope, the team believes that they would be able to see much fainter stars orbiting even closer to the supermassive black hole. "If we are lucky, we might capture stars close enough that they actually feel the rotation, the spin, of the black hole," says Andreas Eckart from Cologne University, another of the lead scientists of the project. This would mean astronomers would be able to measure the two quantities, spin and mass, that characterise Sagittarius A* and define space and time around it. "That would be again a completely different level of testing relativity," says Eckart.

This research was presented in the paper "Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole" to appear in Astronomy & Astrophysics.




Explore further
Supermassive black hole at the center of our galaxy may have a friend



[b]More information:[/b] Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole, Astronomy & Astrophysics (2020). DOI: 10.1051/0004-6361/202037813 , https://www.aanda.org/articles … 3-20/aa37813-20.html
[b]Journal information:[/b] Astronomy & Astrophysics
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#18
APRIL 20, 2020
LIGO and Virgo detectors catch first gravitational wave from binary black hole merger with unequal masses
[Image: ligoandvirgo.jpg]Binary black hole merger where the two black holes have distinctly different masses of about 8 and 30 times that of our Sun. Credit: N. Fischer, H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes project
The expectations of the gravitational-wave research community have been fulfilled: gravitational-wave discoveries are now part of their daily work as they have identified in the past observing run, O3, new gravitational-wave candidates about once a week. But now, the researchers have published a remarkable signal unlike any of those seen before: GW190412 is the first observation of a binary black hole merger where the two black holes have distinctly different masses of about 8 and 30 times that of our Sun. This not only has allowed more precise measurements of the system's astrophysical properties, but it has also enabled the LIGO/Virgo scientists to verify a so far untested prediction of Einstein's theory of general relativity.

"For the very first time we have 'heard' in GW190412 the unmistakable gravitational-wave hum of a higher harmonic, similar to overtones of musical instruments," explains Frank Ohme, leader of the Independent Max Planck Research Group "Binary Merger Observations and Numerical Relativity" at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Hannover. "In systems with unequal masses like GW190412—our first observation of this type—these overtones in the gravitational-wave signal are much louder than in our usual observations. This is why we couldn't hear them before, but in GW190412, we finally can." This observation once again confirms Einstein's theory of general relativity, which predicts the existence of these higher harmonics, i.e. gravitational waves at two or three times the fundamental frequency observed so far.
"The black holes at the heart of GW190412 have 8 and 30 times the mass of our Sun, respectively. This is the first binary black-hole system we have observed for which the difference between the masses of the two black holes is so large!" says Roberto Cotesta, a Ph.D. student in the "Astrophysical and Cosmological Relativity" division at the AEI in Potsdam. "This big mass difference means that we can more precisely measure several properties of the system: its distance to us, the angle we look at it, and how fast the heavy black hole spins around its axis."
[b]A signal like none before[/b]
GW190412 was observed by both LIGO detectors and the Virgo detector on 12th of April 2019, early during the detectors' third observation run O3. Analyses reveal that the merger happened at a distance of 1.9 to 2.9 billion light-years from Earth. The new unequal mass system is a unique discovery since all binaries observed previously by the LIGO and Virgo detectors consisted of two roughly similar masses.

Unequal masses imprint themselves on the observed gravitational-wave signal, which in turn allow scientists to more precisely measure certain astrophysical properties of the system. The presence of higher harmonics makes it possible to break an ambiguity between the distance to the system and the angle we look at its orbital plane; therefore these properties can be measured with higher precision than in equal-mass systems without higher harmonics.

"During O1 and O2, we have observed the tip of the iceberg of the binary population composed of stellar-mass black holes," says Alessandra Buonanno, director of the "Astrophysical and Cosmological Relativity" division at the AEI in Potsdam and College Park professor at the University of Maryland. "Thanks to the improved sensitivity, GW190412 has begun to reveal us a more diverse, submerged population, characterized by mass asymmetry as large as 4 and black holes spinning at about 40% the possible maximum value allowed by general relativity," she adds.
AEI researchers contributed to detecting and analyzing GW190412. They have provided accurate models of the gravitational waves from coalescing black holes that included, for the first time, both the precession of the black-holes' spins and multipole moments beyond the dominant quadrupole. Those features imprinted in the waveform were crucial to extract unique information about the source's properties and carry out tests of general relativity. The high-performance computer clusters "Minerva" and "Hypatia" at AEI Potsdam and "Holodeck" at AEI Hannover contributed significantly to the analysis of the signal.
[b]Testing Einstein's theory[/b]
LIGO/Virgo scientists also used GW190412 to look for deviations of the signals from what Einstein's general theory of relativity predicts. Even though the signal has properties unlike all others found so far, the researchers could find no significant departure from the general-relativistic predictions.
[b]An improved international network of detectors using squeezed light[/b]
This discovery is the second reported from the third observation run (O3) of the international gravitational-wave detector network. Scientists at the three large detectors have made several technological upgrades to the instruments.
"During O3, squeezed light was used to enhance the sensitivity of LIGO and Virgo. This technique of carefully tuning the quantum-mechanical properties of the laser light was pioneered at the German-British detector GEO600," explains Karsten Danzmann, director at the AEI Hannover and director of the Institute for Gravitational Physics at Leibniz University Hannover. "The AEI is leading the world-wide efforts to maximize the degree of squeezing, which has already improved the sensitivity of the GEO600 detector by a factor of two. Our advances in this technology will benefit all future gravitational-wave detectors."
[b]Two done, 54 on the to-do list[/b]
The detector network has issued alerts for 56 possible gravitational-wave events (candidates) in O3 (April 1, 2019 to March 27, 2020 with an interruption for upgrades and commissioning in October 2019). Out of these 56, one other confirmed signal, GW190425, has already been published. LIGO and Virgo scientists are examining all remaining 54 candidates and will publish all those for which detailed follow-up analyses confirm their astrophysical origin.
The observation of GW190412 means that similar systems are probably not as rare as predicted by some models. Therefore, with additional gravitational-wave observations and growing event catalogues in the future, more such signals are to be expected. Each of them could help astronomers better understand how black holes and their binary systems are formed, and shed new light on the fundamental physics of space-time.




Explore further
Researchers find gravitational wave candidates from binary black hole mergers in public LIGO/Virgo data



[b]More information:[/b] GW190412: Observation of a Binary-Black-Hole Coalescence with Asymmetric Masses, arXiv:2004.08342 [astro-ph.HE] https://arxiv.org/abs/2004.08342

https://phys.org/news/2020-04-ligo-virgo...inary.html
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#19
APRIL 29, 2020
Spitzer Telescope reveals the precise timing of a black hole dance
[Image: spitzerteles.jpg]This image shows two massive black holes in the OJ 287 galaxy. The smaller black hole orbits the larger one, which is also surrounded by a disk of gas. When the smaller black hole crashes through the disk, it produces a flare brighter than 1 trillion stars. Credit: NASA/JPL-Caltech
Black holes aren't stationary in space; in fact, they can be quite active in their movements. But because they are completely dark and can't be observed directly, they're not easy to study. Scientists have finally figured out the precise timing of a complicated dance between two enormous black holes, revealing hidden details about the physical characteristics of these mysterious cosmic objects.

The OJ 287 galaxy hosts one of the largest black holes ever found, with over 18 billion times the mass of our Sun. Orbiting this behemoth is another black hole with about 150 million times the Sun's mass. Twice every 12 years, the smaller black hole crashes through the enormous disk of gas surrounding its larger companion, creating a flash of light brighter than a trillion stars—brighter, even, than the entire Milky Way galaxy. The light takes 3.5 billion years to reach Earth.
But the smaller black hole's orbit is oblong, not circular, and it's irregular: It shifts position with each loop around the bigger black hole and is tilted relative to the disk of gas. When the smaller black hole crashes through the disk, it creates two expanding bubbles of hot gas that move away from the disk in opposite directions, and in less than 48 hours the system appears to quadruple in brightness.
Because of the irregular orbit, the black hole collides with the disk at different times during each 12-year orbit. Sometimes the flares appear as little as one year apart; other times, as much as 10 years apart. Attempts to model the orbit and predict when the flares would occur took decades, but in 2010, scientists created a model that could predict their occurrence to within about one to three weeks. They demonstrated that their model was correct by predicting the appearance of a flare in December 2015 to within three weeks.
Then, in 2018, a group of scientists led by Lankeswar Dey, a graduate student at the Tata Institute of Fundamental Research in Mumbai, India, published a paper with an even more detailed model they claimed would be able to predict the timing of future flares to within four hours. In a new study published in the Astrophysical Journal Letters, those scientists report that their accurate prediction of a flare that occurred on July 31, 2019, confirms the model is correct.
The observation of that flare almost didn't happen. Because OJ 287 was on the opposite side of the Sun from Earth, out of view of all telescopes on the ground and in Earth orbit, the black hole wouldn't come back into view of those telescopes until early September, long after the flare had faded. But the system was within view of NASA's Spitzer Space Telescope, which the agency retired in January 2020.

After 16 years of operations, the spacecraft's orbit had placed it 158 million miles (254 million kilometers) from Earth, or more than 600 times the distance between Earth and the Moon. From this vantage point, Spitzer could observe the system from July 31 (the same day the flare was expected to appear) to early September, when OJ 287 would become observable to telescopes on Earth.
"When I first checked the visibility of OJ 287, I was shocked to find that it became visible to Spitzer right on the day when the next flare was predicted to occur," said Seppo Laine, an associate staff scientist at Caltech/IPAC in Pasadena, California, who oversaw Spitzer's observations of the system. "It was extremely fortunate that we would be able to capture the peak of this flare with Spitzer, because no other human-made instruments were capable of achieving this feat at that specific point in time."
[b]Ripples in Space[/b]
Scientists regularly model the orbits of small objects in our solar system, like a comet looping around the Sun, taking into account the factors that will most significantly influence their motion. For that comet, the Sun's gravity is usually the dominant force, but the gravitational pull of nearby planets can change its path, too.

The OJ 287 galaxy hosts one of the largest black holes ever found, with over 18 billion times the mass of our Sun. Orbiting this behemoth is another massive black hole. Twice every 12 years, the smaller black hole crashes through the enormous disk of gas surrounding its larger companion, creating a flash of light brighter than a trillion stars. Credit: Jet Propulsion Laboratory
Determining the motion of two enormous black holes is much more complex. Scientists must account for factors that might not noticeably impact smaller objects; chief among them are something called gravitational waves. Einstein's theory of general relativity describes gravity as the warping of space by an object's mass. When an object moves through space, the distortions turn into waves. Einstein predicted the existence of gravitational waves in 1916, but they weren't observed directly until 2015 by the Laser Interferometer Gravitational Wave Observatory (LIGO).
The larger an object's mass, the larger and more energetic the gravitational waves it creates. In the OJ 287 system, scientists expect the gravitational waves to be so large that they can carry enough energy away from the system to measurably alter the smaller black hole's orbit—and therefore timing of the flares.
While previous studies of OJ 287 have accounted for gravitational waves, the 2018 model is the most detailed yet. By incorporating information gathered from LIGO's detections of gravitational waves, it refines the window in which a flare is expected to occur to just 1 1/2 days.
To further refine the prediction of the flares to just four hours, the scientists folded in details about the larger black hole's physical characteristics. Specifically, the new model incorporates something called the "no-hair" theorem of black holes.
Published in the 1960s by a group of physicists that included Stephen Hawking, the theorem makes a prediction about the nature of black hole "surfaces." While black holes don't have true surfaces, scientists know there is a boundary around them beyond which nothing—not even light—can escape. Some ideas posit that the outer edge, called the event horizon, could be bumpy or irregular, but the no-hair theorem posits that the "surface" has no such features, not even hair (the theorem's name was a joke).
In other words, if one were to cut the black hole down the middle along its rotational axis, the surface would be symmetric. (The Earth's rotational axis is almost perfectly aligned with its North and South Poles. If you cut the planet in half along that axis and compared the two halves, you would find that our planet is mostly symmetric, though features like oceans and mountains create some small variations between the halves.)
[b]Finding Symmetry[/b]
In the 1970s, Caltech professor emeritus Kip Thorne described how this scenario—a satellite orbiting a massive black hole—could potentially reveal whether the black hole's surface was smooth or bumpy. By correctly anticipating the smaller black hole's orbit with such precision, the new model supports the no-hair theorem, meaning our basic understanding of these incredibly strange cosmic objects is correct. The OJ 287 system, in other words, supports the idea that black hole surfaces are symmetric along their rotational axes.
So how does the smoothness of the massive black hole's surface impact the timing of the smaller black hole's orbit? That orbit is determined mostly by the mass of the larger black hole. If it grew more massive or shed some of its heft, that would change the size of smaller black hole's orbit. But the distribution of mass matters as well. A massive bulge on one side of the larger black hole would distort the space around it differently than if the black hole were symmetric. That would then alter the smaller black hole's path as it orbits its companion and measurably change the timing of the black hole's collision with the disk on that particular orbit.
"It is important to black hole scientists that we prove or disprove the no-hair theorem. Without it, we cannot trust that black holes as envisaged by Hawking and others exist at all," said Mauri Valtonen, an astrophysicist at University of Turku in Finland and a coauthor on the paper.




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Star survives close call with a black hole



[b]More information:[/b] Seppo Laine et al. Spitzer Observations of the Predicted Eddington Flare from Blazar OJ 287, The Astrophysical Journal (2020). DOI: 10.3847/2041-8213/ab79a4
[b]Journal information:[/b] Astrophysical Journal Letters  Astrophysical Journal [/url]

Provided by 
Jet Propulsion Laboratory

https://phys.org/news/2020-04-spitzer-te...black.html






APRIL 30, 2020
Clearing up a supermassive (black hole) confusion
[Image: 19-.jpg]The Mercator telescope on La Palma, Spain. Image credit: Péter I. Pápics
Black holes are among the most enigmatic objects in our universe. These mysterious celestial bodies do not emit any light of their own and are thus incredibly difficult to spot. In fact, one can only detect black holes based on the effects that they have on their surroundings. Black-holes come in various flavors and sizes, from 'small' stellar-mass black holes to supermassive black holes found in the center of galaxies. Stellar-mass black holes are the final remnants of massive stars, born more than 20 to 30 times the mass of our Sun and should only form in certain mass ranges according to current theory. In this context, the claimed discovery, published in the distinguished journal Nature in November 2019, of a black hole 70 times more massive than our Sun caught the attention of the astronomical community.

The system in question, LS V +22 25 or LB-1 in short, was claimed to be a double-star system consisting of an 8 solar mass star and a 70 solar mass black hole that orbit around one another in just 80 days, very much the same way as planets orbit around stars. The data used in the original study showed two spectral signatures that moved in different ways: one clear signature belonging to the star and another, more subtle, that was interpreted as belonging to material around the black hole, thus tracing its orbital motion. Based on the motion of these two signatures, the original authors reached their controversial conclusion.
"A stellar black hole this massive challenges everything we know about massive star evolution," says Michael Abdul-Masih, a Ph.D. student from the KU Leuven Institute of Astronomy in Belgium. "Theory tells us that in this mass range, when a star dies it should completely annihilate itself without leaving anything behind, and certainly not such a massive black hole."
The interpretation of the second signature has since come under scrutiny. Using higher-resolution data from the Flemish-funded Mercator Telescope on the island of La Palma (Spain), the KU Leuven team ran several simulations and concluded that the original interpretation of the system was in fact incorrect.
"As we examined the available data more carefully, we began to realize that something didn't seem quite right" explains Michael Abdul-Masih. "The second signature did not behave as we expected it to. This is when I realized that maybe this second signature is not moving at all, but only appears to do so because of the movement of the star." "It is a little like the fake impression of moving you get while sitting in a train and the train next to you starts moving while you are not.", explains Prof. Hugues Sana of KU Leuven further.
The team quickly tested this interpretation and found that it indeed was able to reproduce the observations without the need of such a massive black hole in the system.
"It was quite exciting when we first saw the results. The simulations matched the observations perfectly and we were able to prove that LB-1 does not contain a 70 solar mass black hole as originally thought," concludes Julia Bodensteiner, another Ph.D. student in the team of Prof. Sana.
The findings of Ph.D. student Abdul-Masih appear in the prestigious journal Nature this week and solve the riddle posed by the claimed presence of a massive black-hole in LB1. Even though astronomers can breathe a sigh of relief that LB-1 does not violate stellar evolution theory, this system is indeed remarkable and will surely be the subject of additional studies in the future.




Explore further
Star survives close call with a black hole



[b]More information:[/b] Jifeng Liu et al. A wide star–black-hole binary system from radial-velocity measurements, Nature (2019). DOI: 10.1038/s41586-019-1766-2

Michael Abdul-Masih et al. On the signature of a 70-solar-mass black hole in LB-1, Nature (2020). DOI: 10.1038/s41586-020-2216-x
[b]Journal information:[/b] Nature 

Provided by [url=https://phys.org/partners/ku-leuven/]KU Leuven 

https://phys.org/news/2020-04-supermassi...-hole.html






APRIL 30, 2020
Future detectors to detect millions of black holes and the evolution of the universe
[Image: futuredetect.jpg]An artist's impression of two black holes about to collide and merge. Credit: MARK GARLICK / SCIENCE PHOTO / GETTY IMAGES
Gravitational-wave astronomy provides a unique new way to study the expansion history of the Universe. On 17 August 2017, the LIGO and Virgo collaborations first detected gravitational waves from a pair of neutron stairs merging. The gravitational wave signal was accompanied by a range of counterparts identified with electromagnetic telescopes.

This multi-messenger discovery allowed astronomers to directly measure the Hubble constant—a unit of measurement that tells us how fast the Universe is expanding. A recent study by the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) led by researchers Zhiqiang You and Xingjiang Zhu (Monash University), studied an alternative way to do cosmology with gravitational-wave observations.
In comparison to neutron star mergers, black hole mergers are much more abundant sources of gravitational waves. Whereas there have been only two neutron star mergers detected so far, LIGO and Virgo collaborations have published 10 binary black hole merger events and dozens more candidates have been reported.
Unfortunately, no electromagnetic emission is expected from black hole mergers. Theoretical modeling of supernovae—powerful and luminous stellar explosions—suggests that there is a gap in the masses of black holes around 45-60 times the mass of our Sun. Some inconclusive evidence that supports this mass gap was found in observations made in the first two observing runs of LIGO and Virgo. The new OzGrav research shows that this unique feature in the black hole mass spectrum can help determine the expansion history of our Universe using gravitational-wave data alone.
OzGrav Ph.D. student and first author Zhiqiang You says: "Our work studied the prospect with third-generation gravitational-wave detectors, which will allow us to see every binary black hole merger in the Universe."
Apart from the Hubble constant, there are other factors that can affect how black hole masses are distributed. For example, scientists are still uncertain about the exact location of the black hole mass gap and how the number of black hole mergers evolves over the cosmic history.
The new study demonstrates that it is possible to simultaneously measure black hole masses along with the Hubble constant. It was found that a third-generation detector like the Einstein Telescope or the Cosmic Explorer should measure the Hubble constant to better than one percent within one-year's operation. Moreover, with merely one-week observation, the study revealed it is possible to distinguish the standard dark energy-dark matter cosmology with its simple alternatives.




Explore further
Researchers find gravitational wave candidates from binary black hole mergers in public LIGO/Virgo data



[b]More information:[/b] Zhi-Qiang You, et al. Standard-siren cosmology using gravitational waves from binary black holes, arxiv.org/abs/2004.00036. arXiv:2004.00036v1 [astro-ph.CO]
Provided by ARC Centre of Excellence for Gravitational Wave Discovery 

https://phys.org/news/2020-04-future-det...holes.html
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#20
RCH and angular momentum ???...


JUNE 23, 2020
Experiment confirms 50-year-old theory describing how an alien civilization could exploit a black hole
[Image: 5-blackhole.jpg]Credit: CC0 Public Domain
A 50-year-old theory that began as speculation about how an alien civilization could use a black hole to generate energy has been experimentally verified for the first time in a Glasgow research lab.

In 1969, British physicist Roger Penrose suggested that energy could be generated by lowering an object into the black hole's ergosphere—the outer layer of the black hole's event horizon, where an object would have to move faster than the speed of light in order to remain still.
Penrose predicted that the object would acquire a negative energy in this unusual area of space. By dropping the object and splitting it in two so that one half falls into the black hole while the other is recovered, the recoil action would measure a loss of negative energy—effectively, the recovered half would gain energy extracted from the black hole's rotation. The scale of the engineering challenge the process would require is so great, however, that Penrose suggested only a very advanced, perhaps alien, civilisation would be equal to the task.
Two years later, another physicist named Yakov Zel'dovich suggested the theory could be tested with a more practical, earthbound experiment. He proposed that "twisted" light waves, hitting the surface of a rotating metal cylinder turning at just the right speed, would end up being reflected with additional energy extracted from the cylinder's rotation thanks to a quirk of the rotational doppler effect.
But Zel'dovich's idea has remained solely in the realm of theory since 1971 because, for the experiment to work, his proposed metal cylinder would need to rotate at least a billion times a second—another insurmountable challenge for the current limits of human engineering.
Now, researchers from the University of Glasgow's School of Physics and Astronomy have finally found a way to experimentally demonstrate the effect that Penrose and Zel'dovich proposed by twisting sound instead of light—a much lower frequency source, and thus much more practical to demonstrate in the lab.
In a new paper published today in Nature Physics, the team describe how they built a system which uses small ring of speakers to create a twist in the sound waves analogous to the twist in the light waves proposed by Zel'dovich.

Credit: University of Glasgow
Those twisted sound waves were directed towards a rotating sound absorber made from a foam disc. A set of microphones behind the disc picked up the sound from the speakers as it passed through the disc, which steadily increased the speed of its spin.

What the team were looking to hear in order to know that Penrose and Zel'dovich's theories were correct was a distinctive change in the frequency and amplitude of the sound waves as they traveled through the disc, caused by that quirk of the doppler effect.
Marion Cromb, a Ph.D. student in the University's School of Physics and Astronomy, is the paper's lead author. Marion said: "The linear version of the doppler effect is familiar to most people as the phenomenon that occurs as the pitch of an ambulance siren appears to rise as it approaches the listener but drops as it heads away. It appears to rise because the sound waves are reaching the listener more frequently as the ambulance nears, then less frequently as it passes.
"The rotational doppler effect is similar, but the effect is confined to a circular space. The twisted sound waves change their pitch when measured from the point of view of the rotating surface. If the surface rotates fast enough then the sound frequency can do something very strange—it can go from a positive frequency to a negative one, and in doing so steal some energy from the rotation of the surface."
As the speed of the spinning disc increases during the researchers' experiment, the pitch of the sound from the speakers drops until it becomes too low to hear. Then, the pitch rises back up again until it reaches its previous pitch—but louder, with amplitude of up to 30% greater than the original sound coming from the speakers.
Marion added: "What we heard during our experiment was extraordinary. What's happening is that the frequency of the sound waves is being doppler-shifted to zero as the spin speed increases. When the sound starts back up again, it's because the waves have been shifted from a positive frequency to a negative frequency. Those negative-frequency waves are capable of taking some of the energy from the spinning foam disc, becoming louder in the process—just as Zel'dovich proposed in 1971."
Professor Daniele Faccio, also of the University of Glasgow's School of Physics and Astronomy, is a co-author on the paper. Prof Faccio added: "We're thrilled to have been able to experimentally verify some extremely odd physics a half-century after the theory was first proposed. It's strange to think that we've been able to confirm a half-century-old theory with cosmic origins here in our lab in the west of Scotland, but we think it will open up a lot of new avenues of scientific exploration. We're keen to see how we can investigate the effect on different sources such as electromagnetic waves in the near future."
The research team's paper, titled "Amplification of waves from a rotating body," is published in Nature Physics.


in-duck-ted.

[Image: fig_00387_kelvinwake_2.png]

Quack.



[Image: luminet.jpg]

Quote: Wrote:You can also see that one side of the accretion disc is brighter than the other. This effect is called relativistic beaming, and it's caused by the rotation of the disc. The part of the disc that is moving towards us is brighter because it is moving close to light-speed. This motion produces a change in frequency in the wavelength of the light. It's called the Doppler effect.

The side that's moving away from us, therefore, is dimmer, because that motion has the opposite effect.
"It is precisely this strong asymmetry of apparent luminosity," Luminet wrote in a paper last year, "that is the main signature of a black hole, the only celestial object able to give the internal regions of an accretion disk a speed of rotation close to the speed of light and to induce a very strong Doppler effect."
[Image: 26459820962_9db0403650_c.jpg]

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Reversal of orbital angular momentum arising from an extreme Doppler shift



[b]More information:[/b] Marion Cromb et al. Amplification of waves from a rotating body, Nature Physics (2020). DOI: 10.1038/s41567-020-0944-3
[b]Journal information:[/b] Nature Physics [/url]

Provided by [url=https://phys.org/partners/university-of-glasgow/]University of Glasgow



https://phys.org/news/2020-06-year-old-t...ploit.html
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With a forked tongue the snake singsss...
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#21
...

From the bottom of the last link posted


Quote:... twisting sound instead of light—a much lower frequency source,

The twisted sound waves change their pitch Whistle
when measured from the point of view of the rotating surface. 
If the surface rotates fast enough,
then the sound frequency can do something very strange --
it can go from a positive frequency to a negative one, 
and in doing so steal some energy from the rotation of the surface."


Prof Faccio added:
 "We're thrilled to have been able to experimentally verify some extremely odd physics,
a half-century  Sheep after the theory was first proposed. 

It's strange to think that we've been able to confirm a half-century-old theory,
with cosmic origins here in our lab in the west of Scotland, 
but we think it will open up a lot of new avenues of scientific exploration. 

We're keen to see how we can investigate the effect Whip
on different sources,
such as electromagnetic waves in the near future."

The research team's paper, titled "Amplification of waves from a rotating body,"


The gist of all that above,
reminded me of those spinning flying tic tacs in the pentagon UFO's.
My assumption is that they will try electromagnetic waves amplified on a rotating body next.
...
Reply
#22
JULY 15, 2020
Cases of black hole mistaken identity
[Image: casesofblack.jpg]Credit: X-ray: NASA/CXC/Penn State/B.Luo et al; Illustration: NASA/CXC/M. Weiss
Astronomers have discovered one type of growing supermassive black hole masquerading as another, thanks to a suite of telescopes including NASA's Chandra X-ray Observatory. The true identity of these black holes helps solve a long-running mystery in astrophysics.

The misidentified black holes are from a survey known as the Chandra Deep Field-South (CDF-S), the deepest X-ray image ever taken.
Supermassive black holes grow by pulling in surrounding material, which is heated and produces radiation at a wide range of wavelengths including X-rays. Many astronomers think this growth includes a phase, which happened billions of years ago, when a dense cocoon of dust and gas covers most black holes. These cocoons of material are the fuel source that enables the black hole to grow and generate radiation.
Based on the current picture held by astronomers many black holes immersed in such a cocoon (referred to as "heavily obscured" black holes) should exist. However, this type of growing black hole is notoriously difficult to find, and until now the observed number has fallen short of predictions—even in the deepest images like the CDF-S.
"With our new identifications we've found a bunch of heavily obscured black holes that had previously been missed," said Erini Lambrides of Johns Hopkins University (JHU) in Baltimore, Maryland, who led the study. "We like to say we found these giant black holes, but they were really there all along."
The latest study combined over 80 days of Chandra observing time in the CDF-S with large amounts of data at different wavelengths from other observatories, including NASA's Hubble Space Telescope and NASA's Spitzer Space Telescope. The team looked at black holes located 5 billion light years or more away from Earth. At these distances, scientists had already found 67 heavily obscured, growing black holes with both X-ray and infrared data in the CDF-S. In this latest study, the authors identified another 28.
These 28 supermassive black holes were previously categorized differently—either as slowly growing black holes with low density or nonexistent cocoons, or as distant galaxies.
"This could be considered a case of mistaken black hole identity," said co-author Marco Chiaberge of Space Telescope Science Institute in Baltimore, Maryland, "but these black holes are exceptionally good at hiding exactly what they are."

Lambrides and her colleagues compared their data with expectations for a typical growing black hole. Using data from all of the wavelengths except for X-rays, they predicted the amount of X-rays they should be detecting from each black hole. The researchers found a much lower level of X-rays than they expected from 28 sources, which implies that the cocoon around them is about ten times denser than scientists previously estimated for these objects.
Taking the higher density of the cocoon into consideration, the team showed that the misidentified black holes are producing more X-rays than previously thought, but the denser cocoon prevents most of these X-rays from escaping and reaching the Chandra telescope. This implies they are growing more quickly.
Previous groups did not apply the analysis technique adopted by Lambrides and her team, nor did they use the full set of data available for the CDF-S, giving them little information about the density of the cocoons.
These results are important for theoretical models estimating the number of black holes in the universe and their growth rates, including those with different amounts of obscuration (in other words, how dense their cocoons are). Scientists design these models to explain a uniform glow in X-rays across the sky called the "X-ray background," first discovered in the 1960s. Individual growing black holes observed in images like the CDF-S account for most of the X-ray background.
The X-ray background not currently resolved into individual sources is dominated by X-rays with energies above the threshold that Chandra can detect. Heavily obscured black holes are a natural explanation for this unresolved component because lower-energy X-rays are absorbed by the cocoon more than high-energy ones, and therefore are less detectable. The additional heavily obscured black holes reported here help reconcile past differences between the theoretical models and observations.
"It's like the X-ray background is a blurry picture that has been slowly coming into focus for decades," said co-author Roberto Gilli from the National Institute of Astrophysics (INAF) in Bologna, Italy. "Our work has involved understanding the nature of the objects that have been some of the last to be resolved."
In addition to helping explain the X-ray background, these results are important for understanding the evolution of supermassive black holes and their host galaxies. The masses of galaxies and their supermassive black holes are correlated with each other, meaning that the more massive the galaxy the more massive the black hole.
A paper reporting the results of this study is being published in The Astrophysical Journal. The other authors of the paper are Timothy Heckman of JHU; Fabio Vito from Pontificia Universidad Católica de Chile, in Santiago, Chile; and Colin Norman from JHU.
NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science and flight operations from Cambridge and Burlington, Massachusetts.




Explore further
Hungriest of black holes among the most massive in the universe



[b]More information:[/b] A Large Population of Obscured AGN in Disguise as Low Luminosity AGN in Chandra Deep Field South, arxiv.org/abs/2002.00955
[b]Journal information:[/b] Astrophysical Journal [/url]

Provided by 
Chandra X-ray Center



https://phys.org/news/2020-07-cases-blac...ntity.html





JULY 16, 2020
In a first, astronomers watch a black hole's corona disappear, then reappear
[Image: inafirstastr.jpg]This diagram shows how a shifting feature, called a corona, can create a flare of X-rays around a black hole. The corona (feature represented in purplish colors) gathers inward (left), becoming brighter, before shooting away from the black hole (middle and right). Astronomers don't know why the coronas shift, but they have learned that this process leads to a brightening of X-ray light that can be observed by telescopes. Credit: NASA/JPL-Caltech
It seems the universe has an odd sense of humor. While a crown-encrusted virus has run roughshod over the world, another entirely different corona about 100 million light years from Earth has mysteriously disappeared.

For the first time, astronomers at MIT and elsewhere have watched as a supermassive black hole's own corona, the ultrabright, billion-degree ring of high-energy particles that encircles a black hole's event horizon, was abruptly destroyed.
The cause of this dramatic transformation is unclear, though the researchers guess that the source of the calamity may have been a star caught in the black hole's gravitational pull. Like a pebble tossed into a gearbox, the star may have ricocheted through the black hole's disk of swirling material, causing everything in the vicinity, including the corona's high-energy particles, to suddenly plummet into the black hole.
The result, as the astronomers observed, was a precipitous and surprising drop in the black hole's brightness, by a factor of 10,000, in under just one year.
"We expect that luminosity changes this big should vary on timescales of many thousands to millions of years," says Erin Kara, assistant professor of physics at MIT. "But in this object, we saw it change by 10,000 over a year, and it even changed by a factor of 100 in eight hours, which is just totally unheard of and really mind-boggling."
Following the corona's disappearance, astronomers continued to watch as the black hole began to slowly pull together material from its outer edges to reform its swirling accretion disk, which in turn began to spin up high-energy X-rays close to the black hole's event horizon. In this way, in just a few months, the black hole was able to generate a new corona, almost back to its original luminosity.
"This seems to be the first time we've ever seen a corona first of all disappear, but then also rebuild itself, and we're watching this in real-time," Kara says. "This will be really important to understanding how a black hole's corona is heated and powered in the first place."
Kara and her co-authors, including lead author Claudio Ricci of Universidad Diego Portales in Santiago, Chile, have published their findings today in Astrophysical Journal Letters. Co-authors from MIT include Ron Remillard, and Dheeraj Pasham.
[b]A nimble washing machine[/b]
In March 2018, an unexpected burst lit up the view of ASSASN, the All-Sky Automated Survey for Super-Novae, that surveys the entire night sky for supernova activity. The survey recorded a flash from 1ES 1927+654, an active galactic nucleus, or AGN, that is a type of supermassive black hole with higher-than-normal brightness at the center of a galaxy. ASSASN observed that the object's brightness jumped to about 40 times its normal luminosity.

"This was an AGN that we sort of knew about, but it wasn't very special," Kara says. "Then they noticed that this run-of-the-mill AGN became suddenly bright, which got our attention, and we started pointing lots of other telescopes in lots of other wavelengths to look at it."
The team used multiple telescopes to observe the black hole in the X-ray, optical, and ultraviolet wave bands. Most of these telescopes were pointed at the the black hole periodically, for example recording observations for an entire day, every six months. The team also watched the black hole daily with NASA's NICER, a much smaller X-ray telescope, that is installed aboard the International Space Station, with detectors developed and built by researchers at MIT.
"NICER is great because it's so nimble," Kara says. "It's this little washing machine bouncing around the ISS, and it can collect a ton of X-ray photons. Every day, NICER could take a quick little look at this AGN, then go off and do something else."
With frequent observations, the researchers were able to catch the black hole as it precipitously dropped in brightness, in virtually all the wave bands they measured, and especially in the high-energy X-ray band—an observation that signaled that the black hole's corona had completely and suddenly vaporized.
"After ASSASN saw it go through this huge crazy outburst, we watched as the corona disappeared," Kara recalls. "It became undetectable, which we have never seen before."
[b]A jolting flash[/b]
Physicists are unsure exactly what causes a corona to form, but they believe it has something to do with the configuration of magnetic field lines that run through a black hole's accretion disk. At the outer regions of a black hole's swirling disk of material, magnetic field lines are more or less in a straightforward configuration. Closer in, and especially near the event horizon, material circles with more energy, in a way that may cause magnetic field lines to twist and break, then reconnect. This tangle of magnetic energy could spin up particles swirling close to the black hole, to the level of high-energy X-rays, forming the crown-like corona that encircles the black hole.
Kara and her colleagues believe that if a wayward star was indeed the culprit in the corona's disappearance, it would have first been shredded apart by the black hole's gravitational pull, scattering stellar debris across the accretion disk. This may have caused the temporary flash in brightness that ASSASN captured. This "tidal disruption," as astronomers call such a jolting event, would have triggered much of the material in the disk to suddenly fall into the black hole. It also might have thrown the disk's magnetic field lines out of whack in a way that it could no longer generate and support a high-energy corona.
This last point is a potentially important one for understanding how coronas first form. Depending on the mass of a black hole, there is a certain radius within which a star will most certainly be pulled in by a black hole's gravity.
"What that tells us is that, if all the action is happening within that tidal disruption radius, that means the magnetic field configuration that's supporting the corona must be within that radius," Kara says. "Which means that, for any normal corona, the magnetic fields within that radius are what's responsible for creating a corona."
The researchers calculated that if a star indeed was the cause of the black hole's missing corona, and if a corona were to form in a supermassive black hole of similar size, it would do so within a radius of about four light minutes—a distance that roughly translates to about 75 million kilometers from the black hole's center.
"With the caveat that this event happened from a stellar tidal disruption, this would be some of the strictest constraints we have on where the corona must exist," Kara says.
The corona has since reformed, lighting up in high-energy X-rays which the team was also able to observe. It's not as bright as it once was, but the researchers are continuing to monitor it, though less frequently, to see what more this system has in store.
"We want to keep an eye on it," Kara says. "It's still in this unusual high-flux state, and maybe it'll do something crazy again, so we don't want to miss that."




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Astronomers observe evolution of a black hole as it wolfs down stellar material



[b]Journal information:[/b] Astrophysical Journal Letters 

Provided by [url=https://phys.org/partners/massachusetts-institute-of-technology/]Massachusetts Institute of Technology



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