Xavier Roger
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Astronomers have announced a new kind of black hole after discovering two that are closer to Earth than scientists previously knew of, according to the European Space Agency.
The two black holes, approximately ten times more massive than our planet’s Sun, were discovered by a group of scientists, led Kareem El-Badry, who noticed their companion stars orbiting massive objects, the ESA said in a statement on March 30.
The discovery of Gaia BH1 and Gaia BH2 so close to Earth (just 1,560 light-years away) suggests that “many more similar black holes in wide binaries are still waiting to be discovered.”
“In galactic terms, these black holes reside in our cosmic backyard,” the agency’s statement said.
The “truly black” masses also have the most widely separated orbits of all known black holes, which is probably what makes them completely invisible, only detectable by their gravitational effects.
Until recently, all known black holes were discovered by emission of light, which sets this new group of “practically invisible” black holes apart. Previously discovered black holes emitted light in radio and X-ray wavelengths – produced by material falling into them.
“The new discoveries suggest that black holes in wider binaries are more common.”
How do they know it’s a black hole?
Using data from ESA’s Gaia mission, astronomers measured the positions and motions of billions of stars to discover the black holes and rule out other theories on what the mass that these stars are orbiting could be.
Astronomers can gain essential insights about objects that gravitationally influence these stars, including other stars, exoplanets, and black holes, by observing their movements against the sky.
“The black holes were found by spotting the tiny wobble of its companion star while orbiting around it,” Timo Prusti, ESA’s Gaia project scientist, said. “No other instrument (Gaia) is capable of such measurements.”
Additional measurements from ground-based observatories provided the final evidence to solidify that astronomers had actually detected black holes.
In 2022, Gaia released the first results from its star survey of more than 813,000 binary star systems, providing accurate measurements which led to the discovery of these two black holes. Astronomers will continue to gather information on where these black holes in wide orbits come from.
Gaia’s next data release in 2025 — based on 66 months of observations — will contain more accurate information on the orbits of stars.
More coverage from USA TODAY
Camille Fine is a trending visual producer on USA TODAY’s NOW team.
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