Milky Way center may host 13 black holes

"This finding confirms a major theory and the implications are many," astrophysicist Chuck Hailey said.
By Brooks Hays  |  April 4, 2018 at 2:49 PM
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April 4 (UPI) -- Models predict the supermassive black holes found at the center of most galaxies will be surrounded by a sizable population of smaller black holes. But, until now, astronomers haven't been able to find extra black holes at the center of the Milky Way.

A new study, however, published this week in the journal Nature, suggests at least 13 black holes are positioned near Sagittarius A, the Milky Way's supermassive black hole.

In fact, the research suggests thousands of black holes could be sprinkled throughout the inner regions of the galaxy.

"There are only about five dozen known black holes in the entire galaxy -- 100,000 light years wide -- and there are supposed to be 10,000 to 20,000 of these things in a region just six light years wide that no one has been able to find," Chuck Hailey, an astrophysicist at Columbia University, said in a news release.

Thick clouds of gas and dust block the view deep into the center of the Milky Way, but detectors capable of observing infrared light, radio waves and X-rays offer penetrating views. The most recent investigation of the Milky Way's galactic center used the Chandra telescope to survey X-ray sources near Sagittarius A.

The survey revealed 100 distinct X-ray sources within 13 light-years of the supermassive black hole, 26 of which are located within three light-years.

There are several types of cosmic entities that emit X-rays. Both binary systems -- either with neutron stars or black holes -- and pulsars, highly magnetized rotating neutron stars, give off X-rays. Binary systems with neutron stars produce regular outbursts of high-engery particles. Chandra found no evidence of such outbursts.

While pulsars could account for roughly half of the X-ray sources, astronomers believe the other half are binary systems featuring black holes.

As newer, more powerful observatories and telescopes come online, astronomers will be able to learn more about the unique X-ray sources surrounding Sagittarius A, offering new insights into the ways supermassive black holes evolve and influence the stars and black holes around them. Future analysis of the black hole population surrounding Sagittarius A could also help astronomers understand the propagation of gravitational waves.

"This finding confirms a major theory and the implications are many," Hailey said. "It is going to significantly advance gravitational wave research because knowing the number of black holes in the center of a typical galaxy can help in better predicting how many gravitational wave events may be associated with them. All the information astrophysicists need is at the center of the galaxy."

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