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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156 Comments
  • eva_diva
    eva_divaMonday, February 22, 2021 at 12:37 pm
    i always wonder where would you go if you fell into a black hole?
    • lilchad007822
      lilchad007822Monday, January 11, 2021 at 10:53 am
      this is epic :D
      • maria_goodvibes
        maria_goodvibesThursday, December 10, 2020 at 12:28 pm
        Woah!
        • jkbear
          jkbearTuesday, November 17, 2020 at 12:45 pm
          wow
          • star52
            star52Monday, November 9, 2020 at 11:01 am
            It's behind the milky way, I think
            • noiwantthecandy
              noiwantthecandyMonday, November 2, 2020 at 4:58 am
              I thought there weren't any black holes near earth?
              • tdflame5272007
                tdflame5272007Thursday, March 25, 2021 at 5:55 am
                There are just really far away they don't effect are planet (Earth)
              • dragonhearted
                dragonheartedTuesday, October 13, 2020 at 10:14 am
                if it's right on our backyard then who knows whether if we are getting sucked in already or not.
                • tdflame5272007
                  tdflame5272007Thursday, March 25, 2021 at 5:56 am
                  If we were it would take a long time from the distance
                • ash56100
                  ash56100Wednesday, September 30, 2020 at 8:01 am
                  wow
                  • superdragon
                    superdragonThursday, August 27, 2020 at 11:25 am
                    that is cool but it is also scary
                  • helen0916
                    helen0916Friday, August 14, 2020 at 12:11 am
                    COOL!