Researchers discover black holes that violate the uniqueness theorem and have "gravitational hair."
- Scientists discover that some extreme black holes may violate the "no hair" theorem.
- These black holes feature properties outside of the three classical black hole traits of mass, spin, and charge.
- The researchers ran sophisticated simulations to discover these space oddities.
Black holes are wonderfully weird, sparking the imagination with the many mysteries surrounding their formation and functions in our universe. Now scientists found a new kind of extreme black hole, one that breaks the so-called "ho hair" theorem. In other words, this black hole has "hair."
The idea of the "no hair" or "black hole uniqueness" theorem was encapsulated by the American theoretical physicist John Wheeler who claimed: "Black holes have no hair." What he meant is that black hole solutions to Einstein's field equations of general relativity can be completely characterized by only three physical quantities: mass, spin, and charge. There aren't supposed to be any other "hairy" traits that can make one black hole different from another. Black holes with the same mass, spin, and charge should be identical, explains the press release from Theiss Research, which was behind the new discovery.
The team involved Dr. Lior Burko of Theiss Research, Professor Gaurav Khanna of the University of Massachusetts Dartmouth and the University of Rhode Island, as well as his former student Dr. Subir Sabharwal.
They found there's an extremal black hole that may violate the "no hair" theorem. This type of black hole is "saturated" with the maximum charge or spin it can potentially carry. The researchers discovered that there exists a conserved quantity or property that can be constructed from the spacetime curvature at such a black hole's horizon. It may be measurable from Earth by gravitational wave observatories like LIGO and LISA. Since this property is dependent on how the black hole was formed, it breaks the black hole uniqueness theorem and is considered "gravitational hair."
"This new result is surprising because the black hole uniqueness theorems are well established, and in particular their extension to extreme black holes," shared Dr. Burko. "There has to be an assumption of the theorems that is not satisfied, to explain how the theorems do not apply in this case."
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For their findings, the researchers employed elaborate numerical simulations running on dozens of the top Nvidia graphics-processing-units (GPUs) that had over 5,000 cores each, working in parallel. "Each of these GPUs can perform as many as 7 trillion calculations per second; however, even with such computational capacity the simulations look [sic] many weeks to complete," shared Khanna.
Another type of black hole "hair" was proposed by Stephen Hawking who predicted that quantum particles would leak out of black holes, in a phenomenon dubbed "Hawking radiation." This claim was possibly proven correct by a 2020 study that found evidence of "quantum fuzz" and gravitational wave "echoes" beyond black hole event horizons.
Check out the new study published in Physical Review D.
Baby universes led to black holes and dark matter, proposes a new study.
- Researchers recently used a huge telescope in Hawaii to study primordial black holes.
- These black holes might have formed in the early days from baby universes and may be responsible for dark matter.
- The study also raises the possibility that our own universe may look like a black hole to outside observers.
A new paper takes a deep dive into primordial black holes that were formed as a part of the early universe when there were still no stars or galaxies. Such black holes could account for strange cosmic possibilities, including baby universes and major features of the current state of the cosmos like dark matter.
To study the exotic primordial black holes (PBHs), physicists employed the Hyper Suprime-Cam (HSC) of the huge 8.2m Subaru Telescope operating near the 4,200 meter summit of Mt. Mauna Kea in Hawaii. This enormous digital camera can produce images of the entire Andromeda galaxy every few minutes, helping scientists observe one hundred million stars in one go.
In their study, the scientists considered a number of scenarios, especially linked to the period of inflation. That is the time of quick expansion following the Big Bang, when the universe we know today came into existence with all its structures.
The researchers calculated that in the process of inflation, the climate was ripe for creating primordial black holes of various masses. And some of them reflect the characteristics predicted for dark matter.
Another way PBHs could have been created during inflation is from "baby universes" – small universes that branched off from the main one.
Hyper Suprime-Cam (HSC) is a gigantic digital camera on the Subaru Telescope
Credit: HSC project / NAOJ
A baby or "daughter" universe would ultimately collapse but the tremendous release of energy would lead to the formation of a black hole, explains the press release from the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) in Japan, one of the institutions participating in this study.
What's also fascinating, some of the bigger baby universes might not have gone so quietly. Above a certain critical size, the theory of gravity developed by Albert Einstein permits that such a universe may be perceived differently by observers. If you were inside it, you'd see an expanding universe, while if you were outside, this baby universe would look like a black hole. A conjecture that leads to wondering – are we potentially on the inside or outside of such a universe ourselves?
If you follow this multiverse logic, it also may be possible that while primordial black holes would appear to us as black holes, their true structural natures could be concealed by their "event horizons" – the boundaries surrounding black holes from which not even light can escape.
It should be noted, while strange or counter-intuitive, this is not the first go-around for these types of ideas. A study earlier in 2020 found that so-called "charged" black holes may include within them endlessly-repeating fractal universes of various sizes, including miniature, that can be stretched and deformed in all directions.
To solidify their theories and to find a primordial black hole, the researchers will continue using the Subaru Telescope, with some promising PBH candidates already emerging.
The international team of particle physicists working on the research came from the University of California, Los Angeles and the Kavli Institute. The group included cosmologists and astronomers Alexander Kusenko, Misao Sasaki, Sunao Sugiyama, Masahiro Takada and Volodymyr Takhistov.
Check out their new paper "Exploring Primordial Black Holes from the Multiverse with Optical Telescopes" in Physical Review Letters.
A new study shows our planet is much closer to the supermassive black hole at the galaxy's center than previously estimated.
If you think Earthly matters haven't been going well already, it also turns out that our planet is much closer to the supermassive black hole at the center of the galaxy than we imagined. New observation data allowed researchers to improve the modeling of the Milky Way Galaxy, showing Earth is moving 7 km/s (~16,000 mph) faster and is 2,000 light years closer to the supermassive black hole Sagittarius A*.
The more precise information came from 15 years worth of data collected by the Japanese radio astronomy project VERA, which is a collection of acronyms standing for VLBI Exploration of Radio Astrometry (with "VLBI" meaning Very Long Baseline Interferometry). The project started in 2000 and has the goal of mapping the Milky Way's three-dimensional velocity and spatial structures.
VERA employs interferometry to pull together and combine data from radio telescopes all over the Japanese archipelago. This technique allows the project to get astounding resolution, as good as a telescope with a 2300 km diameter. The measurement is so accurate at this precise resolution of 10 micro-arcseconds, that it would be sufficiently sharp to pick out a U.S. penny if it was somehow left on the Moon's surface.
The VERA Astrometry Catalog and observations made recently by other researchers allowed the astronomers to put together a position and velocity map with a new center for the Galaxy. It's a point around which everything in the Galaxy revolves.
Arrows on this map show position and velocity data for the 224 objects utilized to model the Milky Way Galaxy. The solid black lines point to the positions of the spiral arms of the Galaxy. Colors reflect groups of objects that are part of the same arm, while the background is a simulation image.
The new map claims this center, along with the supermassive black hole it contains, is about 25,800 light-years away from Earth. Notably, this is closer than the distance of 27,700 light years established as the official value in 1985 by the International Astronomical Union.
The new map's velocity component also differentiated the velocity of the planet, showing that it's traveling at 227 km/s in its orbit around the Galactic Center. That's 7 km/s faster than the previously "official" speed of 220 km/s.
VERA next turns its attention to other objects, especially those close to the supermassive black hole at the galaxy's center.
Sir Roger Penrose claims our universe has been through multiple Big Bangs, with more coming.
- Roger Penrose, the 2020 Nobel Prize winner in physics, claims the universe goes through cycles of death and rebirth.
- According to the scientist, there have been multiple Big Bangs, with more on the way.
- Penrose claims that black holes hold clues to the existence of previous universes.
Sir Roger Penrose, a mathematician and physicist from the University of Oxford who has just shared this year's Nobel Prize in physics, claims our universe has gone through multiple Big Bangs, with another one coming in our future.
Penrose received the Nobel for his working out mathematical methods that proved and expanded Albert Einstein's general theory of relativity, and for his discoveries on black holes, which showed how objects that become too dense undergo gravitational collapse into singularities – points of infinite mass.
As he accepted the Prize, Penrose reiterated his belief in what he called "a crazy theory of mine" that the universe will expand until all matter will ultimately decay. And then a new Big Bang will bring a new universe into existence.
"The Big Bang was not the beginning," Penrose said in an interview with The Telegraph. "There was something before the Big Bang and that something is what we will have in our future."
What proof does the physicist have for this theory he dubbed "conformal cyclic cosmology" (CCC) that goes against the current Big Bang dogma? He said he discovered six "warm" sky points (called "Hawking Points") which are all about eight times larger than the diameter of the Moon. The late Professor Stephen Hawking, whose name they bear, proposed that black holes "leak" radiation and would eventually evaporate. As this might take longer than the age of the universe we are currently inhabiting (13.77 billion years old), spotting such holes is very unlikely.
Penrose (89), who collaborated with Hawking, thinks that we are, in fact, able to observe "dead" black holes left by previous universes or "aeons". If proven correct, this would also validate Hawking's theories.
The physicist's 2020 paper, published in the Monthly Notices of the Royal Astronomical Society, offers evidence of "anomalous circular spots" in the cosmic microwave background (CMB) that have raised temperatures. The data revealing the spots came from Planck 70 GHz satellite and was confirmed by up to 10,000 simulations.
Hot spots in Planck CMB data.
Credit: ESA and the Planck Collaboration
Penrose's 2018 paper pinpointed radiation hot spots in the CMB as possibly being produced by evaporating black holes. A 2010 paper by Penrose and Vahe Gurzadyan from the Yerevan Physics Institute in Armenia found support for cyclic cosmology in the uniform temperature rings within the CMB. The scientists proposed then that the rings were caused by signatures of gravitational waves from colliding black holes in a universe that preceded ours.
These ideas are controversial within the cosmologist community, with some pointing to the difficulty of conforming an infinitely big universe in one aeon to a super-small one in the next. This would necessitate making all particles lose mass as the universe gets old.
For another fascinating Penrose theory, check out his views on the quantum-level origins of our consciousness.
Roger Penrose - Did the Universe Begin?
Researchers create a device to test a 50-year-old physics theory from the famed Roger Penrose.
- Scientists prove a 50-year-old physics theory by Roger Penrose.
- The theory explains how energy could be harvested from black holes by advanced aliens.
- Researchers from the University of Glasgow twisted sound waves to show that the effect Penrose described is real.
A theory proposed 50 years ago to explain how energy might be harvested from a black hole was verified by an experiment. Scientists from the University of Glasgow were able to provide first proof for an idea from 1969 by the famed British physicist Roger Penrose, who predicted that only an advanced alien civilization would be able to get energy in the black hole's ergosphere – the outer layer of its event horizon.
Why would it take aliens to do this? Penrose thought that if you lower an object into the ergosphere, you could produce negative energy. But for this to work, the object would have to be moving faster than the speed of light. Penrose envisioned a mechanism that would split an object dropped into the black hole in two, with one part going into the hole while the other would be recovered. As explains the press release from the University of Glasgow, the recoil generated by this process would result in the saved half gaining energy from the black hole's rotation.
Of course if this sounds complicated, it really is and only a very high-tech futuristic civilization would be up for the challenge, concluded Penrose.
What the scientists were able to do now was to test this idea by an experiment based on the proposal from another physicist, Yakov Zel'dovich. He suggested in 1971 that Penrose's theory could be proven by using "twisted" light waves, which would create energy by hitting a rotating metal cylinder and utilizing the rotational Doppler effect.
While Zel'dovich's approach also proved impractical, the scientists from the Glasgow University's School of Physics and Astronomy devised a setup of a small ring of speakers that twisted sound waves in a way similar to how he wanted to twist light. The advantage is that sound waves need a significantly slower rotating surface compared to light.
Check out how the researchers explain their work
The team sent twisted sound waves towards a rotating sound absorber from a foam disk. Microphones positioned in the back of the disk captured the sound that passed from the speakers through the disc, which spun faster and faster.
What the scientists found was that this process produced clear changes in the frequency and amplitude of the sound waves, courtesy of the unusual behavior of the Doppler effect, which normally describes how for example, the pitch of a siren from an emergency vehicle seems to rise as it heads towards you but drops when it moves away. This happens because sound waves come at you with more frequency when the ambulance closes in, but less so after it goes past.
The paper's lead author, Marion Cromb, a Ph.D. student in the University's School of Physics and Astronomy, explained that rotation transforms this linear effect and pulls in energy. "The rotational doppler effect is similar, but the effect is confined to a circular space," he pointed out. "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."
The set-up of the experiment.
Credit: University of Glasgow
The researchers were able to show that as they increased the speed of the spinning disc, the pitch of the sound kept dropping until it disappeared, then it came back up to 30 percent louder than before.
Marion called what they heard during the experiment "extraordinary," adding that the "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."
Whether aliens are using this approach to get energy from black holes is certainly hard to ascertain, but the researchers are planning to investigate whether this effect extends to other sources like electromagnetic waves.
Check out their new paper "Amplification of waves from a rotating body" in Nature Physics.