The largest collision of black holes ever discovered by the LIGO-Virgo scientific collaboration, which includes scientists from the Australian National University, has been observed, and the results of this monitoring have been published in the journal Physical Review. Letters, on September 2.

The short gravitational wave signal (GW190521) captured by the LIGO and Virgo gravitational wave observatories in the United States and Europe on May 21 last year came from two massive, very rotating black holes weighing 85 times and 66 times the mass of the sun, respectively.

Universe brooms

But that is not the only reason why this system is so special.

The largest of these two black holes is considered "impossible".

Astronomers expect that stars between 65 and 130 times the mass of the sun undergo a process called paired instability, which causes the star to explode, leaving nothing behind.

With a mass of 85 solar masses, the largest black hole falls directly into this forbidden range referred to as the black hole's upper mass gap, and it should be "impossible".

So if it wasn't caused by a collapsing star, how did it form?

"We believe that black holes are the vacuum cleaners of the universe. They absorb everything in their tracks, including clouds of gas and stars," said Professor Susan Scott of the School of Physics Research at Australian National University, who is a co-author of the publication.

It also absorbs other black holes and it is possible to produce larger and larger black holes through the continuous collisions of previous generations of black holes. Perhaps the “impossible” black holes heavier in our detected collision could have resulted in this way.

The two black holes merged when the universe was only about 7 billion years old, which is roughly half its current age.

They formed a larger black hole weighing 142 times the mass of the sun, and it is the largest black hole ever detected by observations of gravitational waves.

Medium mass black holes

Black holes with a mass of 100 to 100,000 solar masses are called medium-mass black holes (IMBHs).

They are heavier than stellar-mass black holes, but lighter than supermassive black holes often found in the centers of galaxies.

There were no conclusive electromagnetic observations of medium-mass black holes in the mass range of 100 to 1,000 solar masses.

Professor Scott, who is also a senior researcher at the ARC Center of Excellence for Gravitational Wave Discovery, or OzGrav, says, “We are very excited to have achieved the first direct observation of a black hole in this mass scale. We saw how it formed, confirming that a medium-mass black hole can be produced by merging two small black holes. "

Another recent study suggests that scientists using Caltech's Zwicky Transient Facility may have detected a glow from the collision.

This is surprising, because black holes and their mergers are usually dark to telescopes.

Fill in the gaps of blocks of black holes

"There are a number of different environments in which this two-hole black hole system can form, and the gas disk surrounding the supermassive black hole is certainly one of them," said postdoctoral researcher at Osgrave Dr. Vichali Adya of the National University of Australia.

"But it is also possible that this system consisted of two primitive black holes that were formed in the beginning of the universe."

"Every observation we make of the collision of two black holes gives us new and surprising information about the life of black holes throughout the universe."