There’s a newly-discovered weird asteroid kid on Earth’s block, and it’s moved in close. Really, really close, in space terms.
Asteroid 2009 BD is cruising by us today at a distance of only about 400,000 miles, according to NASA’s Near Earth Object Program. This strange asteroid is estimated to be 5. 7 meters to 13 meters in diameter.
Astronomers will be studying 2009 BD with great interest, because it may be a very rare coorbital asteroid. In 2006, NASA’s Dr. Tony Phillips explained how these type of asteroids corkscrew as they move in tandem with Earth:
These asteroids are called Earth Coorbital Asteroids or “coorbitals” for short. Essentially, they share Earth’s orbit, going around the Sun in almost exactly one year. Occasionally a coorbital catches up to Earth from behind, or vice versa, and the dance begins: The asteroid, while still orbiting the sun, slowly corkscrews around our planet.
Sometimes, coorbitals hang around for awhile:
2004 GU9 is perhaps the most interesting. It measures about 200 meters across, relatively large. And according to calculations just published in the Monthly Notices of the Royal Astronomical Society (S. Mikkola et al., 2006) it has been looping around Earth for 500 years–and may continue looping for another 500. It’s in a remarkably stable “orbit:.
2009 BD will be in Earth’s neighborhood for awhile, giving scientists a change to evaluate it, and its path.