10000 black holes at Milky Way's core, researchers say

Oscar Cross
April 7, 2018

Star formation isn't showing signs of slowing down, and this includes births at the outer edges of the galaxy. Or so it was supposed until now because the accumulation of objects in the area confused astronomers trying to find out what happens in that key region of the galaxy.

USA astrophysicist Dr Chuck Hailey, from Columbia University in New York City, said: "This finding confirms a major theory and the implications are many".

By analyzing the properties and spatial distribution of these X-ray binaries, the researchers extrapolated that 300 to 500 X-ray binaries may lurk in the core of the Milky Way, and about 10,000 isolated black holes without companion stars may also lurk there.

With this in mind, the team realized that to detect black hole binaries, they would have to look for the fainter but steadier X-rays emitted when the celestial pairs are in an inactive state. And since most black holes can't even be spotted that way, they calculate that there are likely thousands of them there.

In short, in the dense net of X-rays emission in the center of Milky Way, black holes were able to remain hidden in plain sight.

But since black holes are black, with nothing - including light - able to escape their mighty grasp, how does one exactly go about finding them? As the normal star evolves, its matter can get sucked up by the black hole or fall onto the neutron star - reaching extremely high temperatures. "They would already have submerged their planets", Charles Hailey explained. Chuck Hailey said, The Independent reported.

They found a dozen of these black hole binaries, and because it's rare for a black hole to grab a star, the scientists can infer that many others are out there that didn't grab a star and are thus invisible.

The map is a literal look back in time to 16 different epochs between 11 and 13 billion years ago. Such confirmations could come from perhaps another decade of additional Chandra observations or from studies by Chandra's proposed successor, a space telescope called Lynx that NASA is presently studying for potential development and launch in the 2020s or 2030s.

"We had no evidence for bunches of black holes before, and our estimates, based on the dozen we see, are consistent with our expectations".

Both these black holes and others from outside the halo are pulled towards Sgr A and held captive around it, scientists believe.

As the galaxies are so far away, they weren't seen in visible light. However, the galactic center is about 26,000 light-years from Earth, and "black hole binaries only very rarely emit big enough bursts of X-rays to easily see at such a great distance as the galactic center - maybe once every 100 or even 1,000 years", Hailey told Space.com.

Another theory is that massive stars, born in gas and dust that surrounds a supermassive black hole, implode to form black holes. This makes the system emit X-rays, which we can detect.

Hailey noted that despite the theory that thousands of black holes should be close to each other, relatively few of the celestial bodies have actually been discovered in the Milky Way. The team searched for those signals in a region stretching about three light-years out from our galaxy's central supermassive black hole.

Hailey said the new findings could significantly advance research into one of the most exciting fields of astronomy right now: gravitational waves. "So you have to separate out the boring X-ray sources from the fun stuff-the black holes".

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