New study suggests tens of thousands of black holes exist in Milky Way's center

A Columbia University-led team of astrophysicists has discovered a dozen black holes gathered around Sagittarius A* (Sgr A*), the supermassive black hole in the center of the Milky Way Galaxy. The finding is the first to support a decades-old prediction, opening up myriad opportunities to better understand the universe.

"Everything you'd ever want to learn about the way big black holes interact with little black holes, you can learn by studying this distribution," said Columbia Astrophysicist Chuck Hailey, co-director of the Columbia Astrophysics Lab and lead author on the study. "The Milky Way is really the only galaxy we have where we can study how supermassive black holes interact with little ones because we simply can't see their interactions in other galaxies. In a sense, this is the only laboratory we have to study this phenomenon."

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At the center of our Milky Way galaxy, sits a supermassive black hole called Sagittarius A*, which has a mass that is 4 million times that of our sun.

Scientists have long thought it unlikely that this black hole is there alone. But they didn’t yet have evidence that these other bodies existed, until now.

As Nell Greenfieldboyce reports for NPR, researchers detected evidence of about a dozen black holes swirling around the galactic center, estimating there could be up to 10,000 isolated black holes in the region.

Black holes emit no visible light or radiation, making them extremely difficult to directly observe using our current technology.

But scientists can study how they interact with bodies nearby. For the latest find, researchers picked up the signal from a star orbiting the black hole, which causes the system to emit X-ray radiation.

Scientists picked through 12 years of data collected by NASA’s Chandra X-Ray Observatory on a search for the telltale radiation within 13 light-years of the galactic center. They found about 100 X-ray sources in that search area, including 26 signals within three light-years of Sagitarrius A*.

Another common object, called a millisecond pulsar, also emits a similar radiation signal as the binary systems. The researchers estimate that about half the signals they detected were from pulsars, leaving 13 X-ray signals coming from black holes with companion stars.

 

In three years, NASA's Fermi has detected more than 100 gamma-ray pulsars, but something new has appeared. Among a type of pulsar with ages typically numbering a billion years or more, Fermi has found one that appears to have been born only millions of years ago.