Astronomers find the closest supermassive black holes to Earth
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Space is filled with black holes, with NASA estimating that there are as many as 10 million to one billion stellar-mass black holes in space. However, scientists often struggle to count them as they are difficult to detect unless they manage to snare some passing material in their gravitational field. Now, an international team of scientists has detected a lone, dormant black hole just under 5,200 light-years away, being well within the borders of the Milky Way galaxy.
The scientists’ discovery, yet to be peer-reviewed, has been uploaded to preprint server arXiv.
Since scientists don’t have the tools to observe a black hole directly, they studied this one by observing the effects on the space around it.
Since this black hole was a quiescent, or inactive black hole, it had a strong gravitational effect around it, warping twisting any light that might travel through it.
This phenomenon, called gravitational microlensing was used to identify small, dim objects that might have otherwise been too difficult for current telescopes to spot.
However, this study is important as it is the first time we’ve ever seen a lone black hole.
The astronomers, led by Kailash Sahu of the Space Telescope Science Institute said: “We report the first unambiguous detection and mass measurement of an isolated stellar-mass black hole.”
“We show that the lens emits no detectable light, which, along with having a mass higher than is possible for a white dwarf or neutron star, confirms its black hole nature.”
According to physicist David Kahana, “Black holes are not like vacuum cleaners.
“They don’t actually suck on the matter near to them and pull it in: they exert gravity and tides on the matter near to them and their rotation also has an effect”
However, the gas and stars can be in a stable orbit around the black hole for a very long time if these are at a safe distance away.
According to Mr Kahana: “If that’s the case for all the gas and stars nearby, then an active black hole will become quiescent – there would be a long period when nothing happens.
“It just sits there and the matter orbits around again and again. It’s called quiescent or dormant during this phase.
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Gravitational microlensing is an observational phenomenon that was first predicted in 1936 by Einstein using his General Theory of Relativity.
This effect occurs when an object with a gravitational field, like a star, passes almost exactly in front of a distant star.
This causes the light rays of the background source star to become bent due to the gravitational “attraction” of the foreground star.
This magnifies the light and also very slightly shifts the apparent position of the distant star.
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