Small asteroid discovered orbiting Earth

Story highlights

  • Earth has an asteroid companion, but it's at least 9 million miles away
  • The asteroid is less than 300 feet in diameter

(CNN)A small asteroid has been found circling Earth as the two objects orbit the sun together.

Scientists say it looks like the asteroid -- called 2016 HO3 -- has been out there for about 50 years and isn't going away anytime soon.
    "Our calculations indicate 2016 HO3 has been a stable quasi-satellite of Earth for almost a century, and it will continue to follow this pattern as Earth's companion for centuries to come," said Paul Chodas, manager of NASA's Center for Near-Earth Object Studies.
    Scientists think the asteroid is between 120 and 300 feet (37 to 91 meters) in diameter. It was found on April 27, 2016 by the Pan-STARRS 1 asteroid survey telescope in Haleakala, Hawaii.
    The asteroid is not going to hit us -- NASA says it never gets closer than 9 million miles (14 million kilometers) from Earth.
    So does this mean Earth has another moon? NASA says that because the asteroid is so far away it can't be considered a natural moon, or satellite. Instead, they're calling it a "quasi-satellite."
    "Since 2016 HO3 loops around our planet, but never ventures very far away as we both go around the sun, we refer to it as a quasi-satellite of Earth," said Chodas in an online press release.
    This isn't the first time Earth has picked up an asteroid companion.
    "One other asteroid -- 2003 YN107 -- followed a similar orbital pattern for a while over 10 years ago, but it has since departed our vicinity. This new asteroid is much more locked onto us," Chodas said.
    And some scientists think there could be other "mini-moons" orbiting the Earth -- some permanent and some temporary.
    In 2012, researchers using a super computer concluded "that at any given time there should be at least one asteroid with a diameter of at least one meter orbiting Earth."
    And there could be many smaller objects orbiting Earth as well.
    NASA's Near Earth Object program keeps track of the objects we know about. And there's a Twitter account where you can follow along.