Five days ago (as of this post) Space Weather newsletter informed that:
CURIOUS ASTEROID FLYBY: Newly-discovered asteroid 2009 BD is slowly passing by Earth today only 400,000 miles away. The approximately 10 meter-wide space rock poses no significant threat, but it merits attention anyway: The orbit of 2009 BD appears to be almost identical to the orbit of Earth. 2009 BD may be a rare “co-orbital asteroid,” circling the sun in near-tandem with our planet. If current measurements of the asteroid’s orbit are correct, 2009 BD will remain in Earth’s neighborhood for many months and possibly years to come.
That day’s newsletter pointed to an older article that detailed the phenomenom:
“2003 YN107 arrived in 1999,” says Paul Chodas of NASA’s Near Earth Object Program at JPL, “and it’s been corkscrewing around Earth ever since.” Because the asteroid is so small and poses no threat, it has attracted little public attention. But Chodas and other experts have been monitoring it. “It’s a very curious object,” he says.
[…]
Future Earth needs coorbital mining contracts, I think.
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.
“These asteroids are not truly captured by Earth’s gravity,” notes Chodas. “But from our point of view, it looks like we have a new moon.”
Astronomers know of at least four small asteroids that can do this trick: 2003 YN107, 2002 AA29, 2004 GU9 and 2001 GO2. “There may be more,” says Chodas. He believes the list will grow as asteroid surveys improve in sky coverage and sensitivity.
(via science@nasa)
