Closest Black Hole Ever Found 1,000 Light-Years From Earth

A team of astronomers has discovered signs of a black hole closer to Earth than any other yet discovered — in a binary star system visible to the naked eye.
Brad Bergan

A newly found black hole could be the closest black hole to Earth, and its home is visible in the night sky to the naked eye, according to a science release on the European Southern Observatory website.


Nearby black hole's home visible to naked eye

The black hole is lurking 1,000 light-years from Earth in the constellation Telescopium — within the southern hemisphere of the sky. The black hole is a resident of a system with two companion stars bright enough to see with the naked eye.

Of course, no one can see the black hole itself, because black holes are so massive that their gravitational pull traps everything — even light — inside the event horizon.

Astronomers first saw this black hole while investigating what appeared to be a binary star system — two stars locked in orbit around a common center of mass. Using the MPG/ESO 2.2-meter telescope based in the La Silla Observatory in Chile, they studied the binary star called HR 6819 as part of a wider study of double-star systems. But when the team put their observations through analysis, they found shocking signs of the universe's most unforgiving phenomenon: a black hole.

HR 6819 ESO
A wide-field view of HR 6819 in the Telescopium constellation. Source: ESO / Digitized Sky Survey 2 / Davide De Martin

How ESO found Earth's the closest black hole

While the astronomers were unable to directly see the black hole, they were able to deduce its presence on the basis of gravitational interactions with the two other stars in the system. Over the course of several months, the astronomers mapped the stars' orbits, and uncovered evidence of a massive and unseen presence enacting gravitational force on the system, reports

The astronomers' observations also revealed that one of the two stars' orbits circles round the invisible behemoth every 40 days, while the other star chills on its own at a much greater distance from the heavy singularity.

After running calculations, the astronomers uncovered the truth: they were dealing with a black hole formed from the collapse of a star roughly four times the mass of our sun.

"An invisible object with a mass at least four times that of the sun can only be a black hole," said Thomas Rivinius, a scientist working with the European Southern Observatory and leader of the new study, in a statement. "This system contains the nearest black hole to Earth that we know of," added Rivinius.

The next-nearest black hole after HR 6819's is roughly 3,000 light-years away from the Earth — in the constellation Monoceros. But the suddenness of this latest nearest big hole in the sky means we're likely to find one even closer. After all, astronomers estimate upward of millions of black holes in the Milky Way.

As for finding the HR 6819 black hole itself, the binary star system looks like a singular, fifth-magnitude star to the naked eye within the constellation of Telescopium, near the edge of another constellation called Pavo (the peacock). On the magnitude scale, the lower the value, the brighter the star. The dimmest objects visible to the naked eye have a magnitude of 6.5. With a magnitude of 5.4 — a little brighter than the planet Uranus, the dimmest of all visible planets — HR 6819 is just within the threshold of human vision.

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