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Binary black hole fusion shaken space-time fabric

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Numerical simulation of two black holes emitting, inducing and merging gravitational waves. Black holes have large and approximately equal masses, one 3% larger than the other. Gravitational wave signal as observed by LGO and Virgo Gravity Wave Detectors on May 21, 2019 (GW190521). Attribution: Attribution: n. Fisher, H. Pfeiffer, a. Buenos Aires (Max Planck Institute for Gravitational Physics) in collaboration with Simulating Extreme SpaceTimes (SXS)

A binary Black hole Merger is likely to occur Gravitational waves Is equal to the energy of eight suns.

For its vast emptiness, the universe sounds through activity in the form of gravitational waves. These echoes, produced by extreme astrophysical phenomena, chase space-time like the cosmos of a cosmic bell.

The signal found what would be the largest black hole fusion ever observed in gravitational waves. The product of the merger was the first clear discovery of an “intermediate-mass” black hole, 100 to 1,000 times the mass of the Sun.

The National Science Foundation’s Laser Interferometer Gravitational-Wave Observatory (May 21, 2019) detected a signal labeled GW190521.LIGO), Similar, 4 km long interferometers in the United States; Kanni, a 3 km long detector in Italy.

The signal is about the same length as about four short wiggles, which is less than one tenth of a second. From what researchers can tell, GW190521 created a source about 5 gigaparse away, about half the age of the universe, one of the farthest gravitational-wave sources ever discovered.

Based on a powerful suite of state – of – the – art computers and modeling equipment, scientists believe that the GW190521 is almost certainly created by a binary black hole fusion with extraordinary properties.

Almost all gravitational-wave signals confirmed to date are from a binary fusion, between two black holes or two neutron stars. This new fusion, which includes two black holes with masses 85 and 66 times the mass of the Sun, appears to be the largest ever.

GW190521 Massive black hole fusion

: This artist’s idea of ​​a hierarchical scheme for merging black holes. LIGO and Virgo recently observed a black hole merging to be 142 times the mass of the Sun, the largest ever observed in gravitational waves. Attribution: LIGO / Caltech / MIT / R.Painting (IPAC)

The LIGO-Virgo team measured the spin of each black hole and found that as the black holes rotated closer to each other, they rotated on their own axis at angles that were not aligned with the axis of their orbit. Improperly designed spins of black holes can cause their orbits to become unstable as two goliaths orbit each other.

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The new signal represents the instantaneous fusion of the two black holes. The fusion created a large black hole with 142 solar masses and a large amount of energy equivalent to eight solar masses scattered throughout the universe in the form of gravitational waves.

Nelson Christensen, a first-time researcher at the French National Center for Scientific Research (CNRS), says: “It’s not like a chiropractor, it’s comparing the signal to the first detection of LGO’s gravitational waves. 2015. “It’s like a ‘bang’, it’s the biggest signal LIGO and Virgo have ever seen.”

An international team of scientists, including the LIGO Scientific Combination (LSC) and the maiden collaboration, reported their findings in two papers published today. One, appears Physical Review Letters, Explains the discovery, another Letters from the Journal of Astronomy, Discusses the physical characteristics of the signal and the astrophysical effects.

“This is done not only by finding black holes of a size that is difficult to explain, but also by using techniques not specifically designed for star fusion,” says Pedro Maronetti, director of the Gravitational Physics Program at National Science. Foundation. This is especially important because it shows the device’s ability to detect signals from completely unexpected astrophysical events. LIGO shows that it can also monitor unexpectedly. ”

In the mass gap

The uniquely large masses of the two exciting black holes and the unique black hole raise a lot of questions about their formation.

All black holes observed to date fall into two categories: star-mass black holes, which measure from a few solar masses to tens of thousands of solar masses and form when large stars die; Or strong black holes in the center of it The Milky Way Galaxy, it’s millions to billions of times the size of our Sun.

However, the last 142-solar-mass black hole produced by the GW190521 fusion is in the intermediate mass range between stellar-mass and supermassive black holes – the first to be discovered.

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The two progenitor black holes that produced the final black hole seem to be unique in their size. They are so large that scientists suspect that they may not have formed from one or two collapsing stars, as most galaxies do.

According to the physics of stellar evolution, external pressure from photons and gas in the core of a star supports the push of gravity inward, so the star is as stable as the sun. Because the nuclei of a giant star are so heavy as iron, they can no longer create the pressure needed to support the outer layers. If this external pressure is less than gravity, the star collapses under its own weight in a core-collapsing supernova explosion that can leave behind a black hole.

This process can explain how stars with 130 solar masses can create black holes with 65 solar masses. But for heavier stars, a phenomenon known as “pair instability” is expected to begin. When the photons in the core get extremely energetic, they can be transformed into an electron and antielectron pair. These pairs produce less pressure than photons, the star becomes unstable against gravitational collapse, and the resulting explosion is strong enough to leave no residue. Stars larger than 200 solar masses will gradually fall directly into a black hole with 120 solar masses. A collapsing star cannot create a black hole between about 65 and 120 solar masses – this range is called the “pair instability mass gap”.

The weight of the two black holes that generated the GW190521 signal at 85 solar masses is the first ever found within the pair instability mass gap.

“The fact that we’ve seen a black hole in this mass gap makes a hole in the heads of many astronomers, and it’s trying to figure out how these black holes were formed,” says Christensen, director of the Artemis Laboratory. Good observatory in France.

One possibility that the researchers will consider in their second paper is a hierarchical fusion in which two small black holes may have formed themselves by merging, before migrating together and finally merging.

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“This event opens up more questions than answers,” says Alan Weinstein, a LIGO member and professor of physics at Caltech. “From the point of view of discovery and physics, this is very exciting.”

“Something Unexpected”

There are still many questions about GW190521.

When LIGO and Virgo detectors hear gravitational waves passing through the earth, they combine automatic searches with incoming data for interesting signals. These searches can use two different methods: algorithms that select specific wave patterns in the data produced by compact binary systems; The more common “explosive” searches, the more likely it is to search for anything out of the ordinary.

LIGO Member Salvatore Vitale, Assistant Professor of Physics With, Comparable to compact binary searches “passing a comb through data, which takes things at a certain distance”, as opposed to exploding more searches in the “catch-all” approach.

In the case of GW190521, a burst search took the signal a little more clearly, opening up the slightest chance of gravitational waves other than a binary fusion.

“The bar to make sure we find something new is very high,” Weinstein says. “So we usually use Ocam’s razor: the simpler the solution, the better. In this case, it’s a binary black hole.”

But what if something new created these gravitational waves? This is a surprising prospect, as in their paper the scientists briefly consider other sources in the universe that may have generated the signal they discovered. For example, a collapsing star in our galaxy may have emitted gravitational waves. It could be a signal from a cosmic string that is generated shortly after the universe has increased in its first moments – although none of these foreign possibilities match data and binary mergers.

“Since we first turned on LIGO, all we have confidently observed is a collision of black holes or neutron stars,” says Weinstein. Although this event is from an unusually large binary black hole merger and alternative explanations are rejected, it pushes the boundaries of our confidence. That would be extremely exciting. Because we all expect something new and unexpected that will challenge what we have already learned. This event has the potential to do just that. ”

Read more about the largest gravitational-wave source of rapid ‘bang’ signals found in this research.


“GW190521: A binary black hole fusion with a total mass of 150 M⊙” r. Abbott et al. (LIGO Scientific Combination and maiden collaboration), 2 September 2020, Physical Review Letters.
DOI: 10.1103 / PhysRevLett.125.101102

R. Abbott, TD Abbott, s. Abraham, f. Arsenal, K. M. Agathos And LIGO Scientific collaboration and maiden collaboration, 2 September 2020, Letters from the Journal of Astronomy.
DOI: 10.3847 / 2041-8213 / aba493

The research was funded by the US National Science Foundation.

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