A newfound black hole may be the closest black hole to Earth, and you can spot its cosmic home in the night sky without a telescope.
The black hole, which is lurking 1,000 light-years from Earth in the southern constellation of Telescopium, belongs to a system with two companion stars that are bright enough to observe with the naked eye. But you won't be able to see the black hole itself; the massive object has such a strong gravitational pull that nothing — not even light — can escape it.
Astronomers discovered this black hole while studying what they thought was just a binary star system, or two stars that orbit a common center of mass. They were using the MPG/ESO 2.2-meter telescope at the La Silla Observatory in Chile to observe the binary, known as HR 6819, as part of a broader study on double star systems. When they analyzed their observations, the researchers were shocked to learn that a third object was hiding in the system: a black hole.
Although the astronomers could not directly observe the black hole, they were able to infer its presence based on its gravitational interactions with the other two objects in the system. By observing the system for several months, they were able to map out the stars' orbits and figure out that another massive, unseen object must be acting in the system.
The observations also showed that one of the two stars orbits the invisible object every 40 days, while the other star hangs out by itself at a much greater distance from the black hole.
They calculated that the object is a stellar-mass black hole — a black hole that forms from the collapse of a dying star — that's about four times the mass of the sun.
"An invisible object with a mass at least four times that of the sun can only be a black hole," Thomas Rivinius, a scientist with the European Southern Observatory who led the new study, said in a statement. "This system contains the nearest black hole to Earth that we know of," he added.
After HR 6819's black hole, the nearest known black hole is about 3,000 light-years away from Earth in the constellation Monoceros. But there could still be others lurking even closer that have yet to be detected; astronomers estimate that there are millions of black holes in our galaxy alone.
The black hole in HR 6819 is one of the first stellar-mass black holes found in our galaxy that does not release bright X-rays while violently interacting with its companion stars, and the discovery could help researchers find other similarly "quiet" black holes in the Milky Way, according to the statement.
"There must be hundreds of millions of black holes out there, but we know about only very few," Rivinius said. "Knowing what to look for should put us in a better position to find them."
How to see HR 6819
While you may not be able to find the black hole while stargazing from your backyard, skywatchers in the Southern Hemisphere can see the stars in the HR 6819 system in the night sky without the help of binoculars or a telescope.
"We were totally surprised when we realised that this is the first stellar system with a black hole that can be seen with the unaided eye," Petr Hadrava, a scientist emeritus at the Academy of Sciences of the Czech Republic in Prague and co-author of the study, said in the statement.
The duo appears as a single, fifth-magnitude star in the modern constellation of Telescopium, near the border with the constellation of Pavo, the peacock. On the magnitude scale, in which smaller numbers denote brighter objects, the faintest objects visible to the human eye are at magnitude 6.5. Currently shining at magnitude 5.4 — just slightly brighter than Uranus, the dimmest visible planet — HR 6819 is just barely bright enough for our eyeballs.
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Hanneke Weitering is an editor at Liv Science's sister site Space.com with 10 years of experience in science journalism. She has previously written for Scholastic Classroom Magazines, MedPage Today and The Joint Institute for Computational Sciences at Oak Ridge National Laboratory. After studying physics at the University of Tennessee in her hometown of Knoxville, she earned her graduate degree in Science, Health and Environmental Reporting (SHERP) from New York University. Hanneke joined the Space.com team in 2016 as a staff writer and producer, covering topics including spaceflight and astronomy.
I am curious. If the blackhole becomes active, would that too be visible with the naked eye?Reply
Every time that I see that there is a new finding that supports the greatest scientific theory of all time, I can't but feel that the true finder is Einstein. All modern scientists do is use technology and learn science principles. But Einstein was the Ali of Science. As M Ali said when he won his first Heavyweight Championship when he was a serious underdog like Einstein and his General Theory was to other scientist "I shocked the world!". Well, Albert, you surely shocked the world! Almost everything you said (except the one addition that your gut didn't want to put in) was correct. Every finding these modern astronomers make is because of you, Einstein.Reply
Wouldn't the closest black hole be found at the center of our galaxy...admin said:A newfound black hole may be the closest black hole to Earth, and you can spot its cosmic home in the night sky without a telescope.
Astronomers discover closest black hole to Earth. And you can 'see' it. : Read more
Presumably there is one there, but why would that have to be the closest one?paperpushermj said:Wouldn't the closest black hole be found at the center of our galaxy...
Question: What is the closest Star to Earthbolide said:Presumably there is one there, but why would that have to be the closest one?
After Sol, Alpha Centauri, four point something ly away. But what does that have to do with the question about a black hole?paperpushermj said:Question: What is the closest Star to Earth
Currently the solar system is 26,000 light years from the center of the Milky Way, putting us 26,000 light years from the black hole in the center.paperpushermj said:Wouldn't the closest black hole be found at the center of our galaxy...
A black hole located only 1,000 light years from us is 26 times closer than the galactic center.
Millions upon millions of black holes are estimated to exist between us and the nucleus of the Milky Way, and just as many on the other side that are further away. Some guesses have more black holes than stars in the galaxy. Plausible, and since it is testable we will know for sure eventually.