We’ve got a new galactic neighbour — a small black hole left over from the death of a fleeting young star.
Astronomers at the European Southern Observatory have found the closest black hole to Earth yet, so near that the two stars dancing with it can be seen by the naked eye.
Of course, close is relative on the galactic scale. This black hole is about 1,000 light-years away, which equates to roughly 9,500 trillion kilometres.
But in terms of the cosmos and even the galaxy, it is in our neighbourhood, according to a study lead by astronomer Thomas Rivinius, who led the study.
The previous closest black hole is probably about three times further, about 3,200 light-years, he said.
The black hole is tiny, only 40 kilometres in diameter, and lives in the Telescopium constellation (the telescope), which neighbours the Sagittarius and Corona Australis constellations in the southern celestial hemisphere.
The discovery of this closer black hole hints that there are more of these out there. Astronomers theorise there are between 100 million to 1 billion of these small but dense objects in the Milky Way.
The trouble is we can’t see them. Nothing, not even light, escapes a black hole’s gravity. Usually, scientists can only spot them when they’re gobbling up sections of a partner star or something else falling into them.
Astronomers think most black holes, including this newly discovered one, don’t have anything close enough to swallow. So they go undetected.
Astronomers found this one because of the unusual orbit of a star. The new black hole is part of what used to be a three-star dance in a system called HR6819.
They’re maybe 140 million years old, but at 15,000 degrees Celsius they are three times hotter than the sun.
“About 15 million years ago, one of those stars got too big and too hot and went supernova, turning into the black hole in a violent process.”
The two remaining stars aren’t close enough to be sucked in, but one star is close enough for its orbit to be warped.
Using a telescope in Chile, astronomers confirmed that there was something about four or five times the mass of our sun pulling on the inner star. It could only be a black hole, they concluded.
Like most of these type of black holes, this one is comparatively small, maybe 40 kilometres in diameter.
“It is most likely that there are black holes much closer than this one,” said Avi Loeb, director of Harvard’s Black Hole Initiative, who wasn’t part of the study.
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