Astronomers Discover Black Hole Hiding In Plain Sight In Earth's "Backyard"

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An artist's illustration of the HR 6819 system. The system comprises two stars (both in blue) orbiting around a black hole (in red) (Credit: ESO/L. Calçada)

Given that each light-year — defined as the distance light travels in one Earth year — is about 6 trillion miles (9 trillion km), a black hole that lies 1,000 light-years away may not seem very close. However, to astronomers who are accustomed to cosmic distance scales, the recently-discovered HR 6819's black hole, which lies in the constellation Telescopium, is an extremely close neighbor.

"On the scale of the Milky Way, it's in our backyard," said Thomas Rivinius, an astronomer at the European Southern Observatory (ESO) in Chile who led the research. "Almost on our doorstep." The scientist says it is so close that the black hole's two orbiting stars can be observed with the naked eye in the Southern Hemisphere's skies on a clear night.

A wide-field image of the region of the sky, in the constellation Telescopium ,where HR 6819 is located (Credit: ESO/Digitized Sky Survey / Davide De Martin / CC BY by/4.0/Creative Commons)

A black hole forms when a massive dying star collapses under its own gravity and shrinks until all of its mass is contained in an infinitely dense point called a singularity. Since black holes do not allow light to escape, they remain invisible until their strong gravitational pull starts to draw in nearby stars. The process is so luminous that it can be observed from Earth. "Sometimes they [black holes] become the brightest objects in the sky," says Erin Kara, an astrophysicist at MIT who studies black holes. However, since HR 6819's two stars are too far away to be pulled in by its gravity, the black hole managed to remain undetected despite being so close to Earth.

“It seems like it’s been hiding in plain sight,” says astronomer Kareem El-Badry, a Ph.D. student at the University of California, Berkeley, who specializes in binary star systems but wasn’t involved with the study. “It’s a bright enough star [system] that people have been studying it since the 80s, but it seems like it’s had some surprises.”

The ESO astronomers stumbled upon the discovery when they began analyzing the data collected on the HR 6819 system as part of their research on stars that orbit in pairs. They found that unlike other binary star systems, which move in synch, HR 6819's inner star was orbiting at a much faster pace than its outer star. This led the astronomers to suspect there was a third object located at the center of the star system. After further investigating the inner star's motion and orbit pattern, the team came to the conclusion that the unseen​​​​​​ body is a black hole – the remnant of a third star which had once been a part of the HR 6819 star system. Their calculations suggest that the black hole has a mass roughly four times that of our Sun.

The discovery, published in the journal Astronomy & Astrophysics on May 6, 2020, is giving scientists hope that there are many more black holes near Earth that are just waiting to be discovered. "It's important to emphasize that it's the closest we've found yet," says Sera Markoff, an astrophysicist at the University of Amsterdam who was not involved with the latest research. "There might be closer ones."

Resources: TheAtlantic.com, Vox.com, Gizmondo.com

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136 Comments
  • elizabethan
    elizabethanThursday, May 28, 2020 at 6:01 am
    That is so cool.Like me if you agree.
    • lizzzy_winkle
      lizzzy_winkleWednesday, May 27, 2020 at 7:19 pm
      It's so pretty.
      • rocketleaguepro
        rocketleagueproWednesday, May 27, 2020 at 12:13 pm
        Ark survival evolved!
        • rocketleaguepro
          rocketleagueproWednesday, May 27, 2020 at 11:37 am
          10 to 20 times the mass of the sun!!😰 the sun can fit millions of earth in it, so just imagine how big it can be if it is a LOT larger than the sun!!☣❕
          • rocketleaguepro
            rocketleagueproWednesday, May 27, 2020 at 10:58 am
            Wow cool! 😎
            • redhat2946
              redhat2946Wednesday, May 27, 2020 at 6:55 am
              I am amazed at how many black holes there could be in the milky way
              • crazytaco1
                crazytaco1Tuesday, May 26, 2020 at 6:59 pm
                Well there are other galaxies so what if that’s what it go’s to🤯
                • whataburger
                  whataburgerTuesday, May 26, 2020 at 3:37 pm
                  Black holes can form form stars and other things or form matter
                  • starwarstnt17
                    starwarstnt17Sunday, May 24, 2020 at 5:58 pm
                    That´s Nice
                    • galaxy_fox12
                      galaxy_fox12Sunday, May 24, 2020 at 11:41 am
                      I wonder what will happen if you fall into a black hole 🧐