In a trio-star system visible with the naked eye
This nearby black hole has evaded detection so far since it's very small, and very quiet - detecting black holes is that much harder when they aren't actively slurping down matter from their surrounding space, since they neither emit nor reflect any detectable radiation whatsoever.
But the newly discovered object had a tell. It's in a triple star system, with two B-type main sequence stars, visible from Earth with the naked eye, and previously thought to be a binary system, called HR 6819.
When astronomers took observations of the system as part of a survey on binary stars, they found something awry. The orbits of those two main sequence stars seemed to be tugged askew.
Follow-up observations tracking the star using the MPG/ESO 2.2-metre telescope at European Southern Observatory's (ESO) La Silla Observatory in Chile clinched it. One of the stars, with an estimated mass between 5 and 7 times the mass of the Sun, orbits a gravitational centre of the system every 40 days - not the other star, which is much farther out.
When analysed, these orbits suggested there were not two, but three objects dancing around each other in orbit. Since the third object was invisible, there was one thing it was far more likely to be than anything else.
"An invisible object with a mass at least four times that of the Sun can only be a black hole," said astronomer Thomas Rivinius of the European Southern Observatory. Therefore, "this system contains the nearest black hole to Earth that we know of."
And it's just over 1,000 light-years away. Previously, the closest known black hole, A 0620-00, was measured at a distance of 3,300 light-years away.
https://www.sciencealert.com/astron...-black-hole-just-1-000-light-years-from-earth
This nearby black hole has evaded detection so far since it's very small, and very quiet - detecting black holes is that much harder when they aren't actively slurping down matter from their surrounding space, since they neither emit nor reflect any detectable radiation whatsoever.
But the newly discovered object had a tell. It's in a triple star system, with two B-type main sequence stars, visible from Earth with the naked eye, and previously thought to be a binary system, called HR 6819.
When astronomers took observations of the system as part of a survey on binary stars, they found something awry. The orbits of those two main sequence stars seemed to be tugged askew.
Follow-up observations tracking the star using the MPG/ESO 2.2-metre telescope at European Southern Observatory's (ESO) La Silla Observatory in Chile clinched it. One of the stars, with an estimated mass between 5 and 7 times the mass of the Sun, orbits a gravitational centre of the system every 40 days - not the other star, which is much farther out.
When analysed, these orbits suggested there were not two, but three objects dancing around each other in orbit. Since the third object was invisible, there was one thing it was far more likely to be than anything else.
"An invisible object with a mass at least four times that of the Sun can only be a black hole," said astronomer Thomas Rivinius of the European Southern Observatory. Therefore, "this system contains the nearest black hole to Earth that we know of."
And it's just over 1,000 light-years away. Previously, the closest known black hole, A 0620-00, was measured at a distance of 3,300 light-years away.
https://www.sciencealert.com/astron...-black-hole-just-1-000-light-years-from-earth
