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Published: Thu, April 05, 2018
Research | By Jennifer Evans

The centre of the Milky Way is teeming with black holes

The centre of the Milky Way is teeming with black holes

The researchers also found that these early galaxies are incredibly compact.

Scientists are already aware of the supermassive black hole at the center of the Milky Way, and now they have discovered thousands more black holes surrounding it. Scientists have speculated that black holes tend to sink to the center of the galaxy and now they may have found proof. "The galactic center is a odd place".

Another theory is that massive stars, born in gas and dust that surrounds a supermassive black hole, implode to form black holes.

Black holes are generally "pretty impossible" to see, according to the physicist.

Astronomers have previously looked for black holes that are gravitationally bound to a companion star, which can provide fuel for very bright X-ray outbursts - but such eruptions are rare. These types of black holes are referred to as black hole binaries.

A search for the X-ray signatures of low-mass black hole binaries in the Chandra data turned up 12 within three light-years of Sgr A*.

Either way, our galaxy's supermassive black hole should be surrounded by hundreds of stellar-mass black holes - at least.

This week, a team of scientists led by Charles Hailey, from the University of Columbia (USA), announced in Nature magazine the discovery of several binary systems in which a part of the couple is a black hole.

In order to prove the theory, the researchers began to look for black holes.

The astronomers were also careful not to be fooled by the many other intriguing X-ray-emitting objects at the galactic centre.

Combing through archival data from NASA's Chandra X-ray Observatory, Charles Hailey at Columbia University in NY and his colleagues were able to finally tease out a signal that appears to be coming from 12 stellar-mass black holes that have sun-sized stars orbiting them.

The discovery can also help refine our ideas of the freakish, rare binary systems that produce gravitational waves. So there's still a lot of empty space and gas amid all those black holes. The collapsed giant stars have a gravitational pull so strong that even light can't get out.

The newly confirmed black holes are about 10 times the mass of our sun, as opposed to the central supermassive black hole, which has the mass of 4 million suns.

Despite telescopes being trained on the galactic centre for more than a decade, astrophysicists have had no joy.

We really think we basically understand how things are happening at the centre of the galaxy. As they suck up all the surrounding gas, the material spirals around it like a whirlpool, creating an accretion disk.

An artist's impression of a black hole binary.

"Our galaxy is quite normal, so if you see tons of black holes here, they must exist in the centres of most galaxies", said Hailey.

"These early galaxies seem to have gone through many more "bursts" when they formed stars, instead of forming them at a relatively steady rate like our own galaxy", Sobral said in a statement.

"Isolated, unmated black holes are just black-they don't do anything".

Morris calls the work "exciting" but notes that due to the very low total numbers of photons used in the analysis, of the dozen putative black holes some might actually merely be statistical flukes produced by coincidentally timed emissions from other sources. Since the ripples are emitted whenever black holes collide, or fall into the center of the galaxy, estimating the population of these black holes might help refine the estimates of the number of gravitational wave events. And, Hailey said, perhaps they will find one at the centre of a distant galaxy. And he hopes that other astronomers will use publicly available data to further seek out these somewhat elusive mysteries of the universe.

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