Astronomers have discovered the two closest black holes to Earth, according to The European Space Agency.
The black holes, Gaia BH1 and Gaia BH2 are located just a few 1560 light-years away. “In galactic terms, these black holes reside in our cosmic backyard,” the agency’s statement said.
The black holes were discovered accidentally when a team of astronomers was studying the movements of their surrounding stars using Gaia data. Gaia data measures with minute accuracy the positions and movements of billions of stars.
While studying the stars, astronomers noticed an odd wobble, as if the stars were orbiting a very massive object. Since no light seemed to be coming from the object, astronomers knew they were dealing with a black hole.
“The accuracy of Gaia’s data was essential for this discovery, Timo Prusti, ESA’s Gaia project scientist, said. “The black holes were found by spotting the tiny wobble of its companion star while orbiting around it. No other instrument is capable of such measurements.”
However, astronomers quickly realized they were dealing with no ordinary black hole. This was a type of black hole they had never seen before.
Before the discovery of Gaia BH1 and Gaia BH2, astronomers discovered black holes by the transmission of light, generally, X-ray and radio wavelength, produced from material falling into the black hole.
However, everything astronomers knew of black holes was turned on its head when they discovered that Gaia BH1 and Gaia BH2 were found, not by light, but by their gravitational effects.
What this means is that these new types of black holes are practically invisible. This discovery of invisible black holes raises questions about more invisible black holes waiting to be discovered. Some astronomers even estimate there could be up to 100 million stellar-mass black holes in the Milky Way alone, not even taking into account the rest of the galaxy.
“Even though we detected nothing, this information is incredibly valuable because it tells us a lot about the environment around a black hole,” said Yvette Cendes, astronomer at Harvard-Smithsonian Center for Astrophysics in the US, and co-discoverer of the black hole. “There are a lot of particles coming off the companion star in the form of stellar wind. But because we didn’t see any radio light, that tells us the black hole isn’t a great eater and not many particles are crossing its event horizon. We don’t know why that is, but we want to find out!”
Interestingly enough, a similar discovery was made in November of 2021 with the finding of NGC 1850; however, there wasn’t sufficient evidence that NGC 1850 was truly a black hole. By doubling down on their research and learning from their mistakes with NGC 1850, this recent discovery of Gaia BH1 and Gaia BH2 leaves no room for doubt.
“For the first time, our team got together to report on a black hole discovery, instead of rejecting one,” said Tomer Shenar, astronomer at Amsterdam University in the Netherlands. “We identified a needle in a haystack.”
Edited by Sean Mulryan
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