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Closest Black Hole

August 21, 2020

Millions of black holes may populate the Milky Way Galaxy. So far, though, only one of them has been found in a star system that’s visible to the unaided eye. HR 6819 is in the constellation Telescopium. Unfortunately, though, it’s visible mainly from the southern hemisphere.

The black hole is the closest to Earth yet seen. It’s about a thousand light-years away — a third of the distance to the previous record holder. It contains two stars that are much bigger, heavier, and brighter than the Sun. Years ago, astronomers took a close look at it with a telescope in Chile. But they filed the observations away without a careful analysis.

But they recently noticed that a similar system might have a black hole. So they took a better look at their data. And they found a hidden presence. One of the bright stars is orbiting an invisible object that’s at least four times the mass of the Sun. If the object was a star it would be easy to see. Since it’s not visible, it must be a black hole.

Unlike most black holes, this one is quiet. Most of the other known black holes — a few dozen in all — are stealing gas from companion stars. The gas forms a hot disk around the black hole that shines brightly. In this case, though, the black hole is too far from its companions to pull away any gas.

Despite its proximity, the black hole is nothing to worry about. It’s so far away that it’s no threat to Earth or the rest of our solar system.

Script by Damond Benningfield

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