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August 26, 2005
earth's second moon
discovered in 1986, earth's "second moon" is called asteroid 3753. her more commonly used name is cruithne (pronounced croo-een-ya), which is the first celtic racio-tribal group that migrated from europe to the british isles sometime in 800-500 bc.
cruithne shares the earth's orbit around the sun - they are co-orbital, sort of like earth's little pet dog.
however, cruithne is not a moon because she is not gravitationally bounded with earth, like luna. her orbit is very complicated - so much so that the path was only mapped out in 1997, 11 years after the discovery.
observe cruithne's orbit(yellow line) in the picture below (mercury is magenta, venus green, earth blue, mars red) :
as you can see, cruithne does not traverse elliptically, but orbits in a horseshoe. for more technical explanation about why she travels like that and whether there is a chance that she bangs earth and how unique the relationship is between these two, read Paul Wiegert's explanation (he was one of the guys who observed and realised cruithne's course)
cruithne is classified as a Near Earth Asteroid (also known as aten asteroid). every 385 years this "moon" comes to its closest point to earth, 15 million km away. this will occur next in 2285.
posted by nyx at August 26, 2005 12:13 AM
Comments
Heheheh, looks like the moon got competition
Posted by: BawangMerah at August 26, 2005 10:38 AM
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