Astronomers have discovered 26 new likely black holes in the neighboring Andromeda galaxy — the largest haul of black hole candidates ever found in a galaxy apart from our own.
Black holes, which emit almost no light themselves, can be seen only by the light given off by material falling into them. The supermassive black holes that populate the centers of most galaxies are easy to spot because their surroundings are so bright, but much smaller stellar mass black holes are considerably harder to find.
The 26 new candidates, in combination with nine previously discovered black holes in Andromeda, bring the known tally in that galaxy to 35.
“While we are excited to find so many black holes in Andromeda, we think it’s just the tip of the iceberg,” Robin Barnard, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., said in a statement. “Most black holes won’t have close companions and will be invisible to us.”
Most of the newfound black holes have about five to 10 times the mass of our sun, and resulted from the deaths of giant stars. Seven of the new candidates were found within 1,000 light-years of the center of the Andromeda galaxy — more than the number of black holes near the core of our own Milky Way.
“We are particularly excited to see so many black hole candidates this close to the center, because we expected to see them and have been searching for years,” Barnard said.
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