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Posted by gb6724 on June 10, 2006, 1:39 pm
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> http://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.
jOURNy thhrough the whitehole status:
When the witch approaches Tarzan and asks what his three
wishes are, she gave him a card and told him to show up at
the address written on it, and the witch disappeared.
When Tarzan showed up at the address, he found other
hunchbacks there holding the same name cards.
More to come.
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