Astronomers from the European Space Observatory have just found the closest black hole to Earth. It lives in a triple system.
Astronomers from the European Southern Observatory (ESO) and other institutes have just found the closest black hole to Earth. It lies about 1,000 light-years from Earth in the southern constellation of Telescopium.
The black hole is closer to our solar system than any other found to date. And you can see its home system with the naked eye.
The researchers found it by accident as they were tracking two stars. The new-found black hole is part of the HR 6819 triple system.
The team found evidence for the black hole by tracking its two companion stars using the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. They say this system could just be the tip of the iceberg, as many more similar black holes could be found in the future.
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“We were totally surprised when we realized that this is the first stellar system with a black hole that can be seen with the unaided eye,” says Petr Hadrava, Emeritus Scientist at the Academy of Sciences of the Czech Republic in Prague and co-author of the research.
“This system contains the nearest black hole to Earth that we know of,” says ESO scientist Thomas Rivinius, who led the study published today in Astronomy & Astrophysics.
By observing the system for several months, they managed to map out the stars’ orbits. Thus figuring out that another massive, invisible object must be acting in the system.
The researchers also found that one of the stars orbits the black hole every 40 days. Meanwhile, the other star hangs out by itself at a much greater distance from the black hole.
“One of the stars is moving periodically, with a period of 40 days,” said Dietrich Baade, an emeritus astronomer at European Southern Observatory (ESO) and a co-author of the study.
“And the only way to understand that period and the very large [velocity] of 60km per second with a mass five times that of the sun was to infer that there is another very massive body which, however, is not visible.”
The HR 6819 black hole probably formed from the gravitational collapse of a massive star.
It is one of the very first stellar-mass black holes discovered that does not interact violently with its environment. And, therefore, appears truly black. Nearly all of the other stellar-mass black holes found so far, strongly interact with their environment and make themselves visible by releasing powerful X-rays in this interaction.
After HR 6819, the nearest known black hole is about 3,000 light-years away from Earth in the constellation Monoceros. But there are likely others lurking even closer, that we haven’t detected yet.
Estimations show there are millions of black holes in our galaxy alone.
The researchers have published their findings on Wednesday in the scientific journal Astronomy & Astrophysics.