[meteorite-list] New Retrograde Asteroid Found

From: lebofsky at lpl.arizona.edu <lebofsky_at_meteoritecentral.com>
Date: Sat, 2 May 2009 13:50:51 -0700 (MST)
Message-ID: <7683bc86977c49a98e3c318cb27d078e.squirrel_at_webmail.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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Received on Sat 02 May 2009 04:50:51 PM PDT