Earth to lose moon

Interesting...



science.nasa.gov/headlines/y2006/09jun_moonlets.htm

Corkscrew Asteroid
NASA Science News
June 9, 2006

A tiny asteroid looping around Earth for the past seven years is about to leave the neighborhood.


June 9, 2006: News flash: Earth has a "second moon." Asteroid 2003 YN107 is looping around our planet once a year. Measuring only 20 meters across, the asteroid is too small to see with the unaided eye—but it is there.

This news, believe it or not, is seven years old.

"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.

Most near-Earth asteroids, when they approach Earth, simply fly by. They come and they go, occasionally making news around the date of closest approach. 2003 YN107 is different: It came and it stayed.

"We believe 2003 YN107 is one of a whole population of near-Earth asteroids that don't just fly by Earth. They pause and corkscrew in our vicinity for years before moving along."

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.

At the moment, only two coorbitals are actually nearby: 2003 YN107 and 2004 GU9. The others are scattered around Earth's orbit.

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."

Right now, however, researchers are paying more attention to 2003 YN107
for one simple reason: it's about to depart. The asteroid's corkscrew
path is lopsided and on June 10th it will dip within 3.4 million km of
Earth, slightly closer than usual. Earth's gravity will then give the
asteroid the nudge it needs to leave.

"This is a chance to observe one of these asteroids [on the way out]," explains Chodas.

It won't be gone forever. In about 60 years 2003 YN107 will lap Earth again, resuming its role as a temporary, corkscrewing moonlet. In due course, other coorbitals will do the same.

Each encounter is an opportunity for study--and possibly profit. Even the most powerful telescopes cannot see much of these tiny asteroids; they're just specks in the eyepiece. But one day, when the space program is more advanced (see the Vision for Space Exploration), it might be possible to visit, explore the moonlets and tap their resources. "For now, they're just a curiosity," says Chodas.

News flash: Earth is about to lose a moon. More to come.

Apostolis Christou (Tolis) at Armagh Observatory specializes in coorbital dynamics of asteroids.

BTW, the Uranium satellite mutual events have just started and will go on for the next 5 years. The last time for these events was back in 1966. There is an opportunity for astrometric positions for these events. It has been sometime since the two Voyagers were at Uranus.

I am not to sure yet how to do the observations with the brightness of Uranus in the same field. Tolis was down with me 2 weeks ago and we discussed observational work on the events. I understand that he will be putting together some constructive approach how to get around this problem.

Eamonn A

Hmmm - 1966 - that sounds familiar....

Hmmm - 1966 - that sounds familiar....

Do you want to get barred for June or something?

~Al (supporting the other 31 teams!)

Surely you'll be following the star-spangled banner? When in Rome...

Of course, I would have gone to Germany had the Boys in Green qualified

Eamonn - I understood that a methane filter could help. If you or Tolis come up with anything other technique though, please let us know.

Cheers

Dave

Hmmm - 1966 - that sounds familiar....

yes it is the year that star trek was first broadcast . nothing else of signficance i can remember from that year.
stephen.