[meteorite-list] New Retrograde Asteroid Found

[lebofsky at lpl.arizona.edu]

Eric:

This sounds like a good candidate for an extinct comet! The big question
is, why it has not been seen before. I am not a dynamicist, so I do not
know if a close encounter by an asteroid to, say the Earth, could put a
"normal" asteroid into a retrograde orbit.

Larry


> A new asteroid was found April 29th orbiting the sun backwards.

> Calculating the orbit of the new asteroid is difficult because

> observational errors could cause a mis-projected orbit. This asteroid

> was close enough

>

> Observational Data: http://www.cfa.harvard.edu/mpec/K09/K09J04.html

>

> Article:

>

> Nearby asteroid found orbiting sun backwards

>

> 23:50 01 May 2009 by Jeff Hecht

> For similar stories, visit the Solar System and Comets and Asteroids

> Topic Guides

> The discovery of a 2- to 3-kilometre-wide asteroid in an orbit that goes

> backwards has set astronomers scratching their heads. It comes closer to

> Earth than any other object in a 'retrograde' orbit, and astronomers

> think they should have spotted it before.

>

> The object, called 2009 HC82, was discovered by the Catalina Sky Survey

> in Arizona on the morning of 29 April.

>

>  From observations of its position by five different groups, Sonia Keys

> of the International Astronomical Union's Minor Planet Center calculated

> it orbits the sun every 3.39 years on a path that ventures within 3.5

> million km of the Earth's orbit. Combined with its size, that makes 2009

> HC82 a potentially hazardous asteroid.

>

> What's really unusual is that the calculated orbit is inclined 155° to

> the plane of the Earth's orbit. That means that as it orbits the Sun, it

> actually travels backwards compared to the planets. It is only the 20th

> asteroid known in a retrograde orbit, a very rare group. None of the

> others comes as close to the Earth.

>

> SOURCE:

> http://www.newscientist.com/article/dn17073-nearby-asteroid-found-orbiting-sun-backwards.html

>

>

> --

> Regards,

> Eric Wichman

> Meteorites USA

> 904-236-5394

>

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