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Re: Earth's Second Moon 10/26/99

Ron, this has got to be one of your best posts ever!!!  Suddenly I feel like
a straight man:-)

Not quite through with the subject though.   I think there may be an
opening, if anyone cares to pursue this..............  otherwise, "I'll be
back"  (Said with the infamous Austrian accent.)

Best Regards,
Julia

-----Original Message-----
From: Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
To: meteorite-list@meteoritecentral.com
<meteorite-list@meteoritecentral.com>
Date: Tuesday, October 26, 1999 12:57 PM
Subject: Re: Earth's Second Moon 10/26/99


|
|>This article shows a very clear diagram of Lagrangian points and gives
|>further insight into co-orbital dynamics.
|>
|>http://sci.esa.int/categories/newsitem.cfm?TypeID=5&ContentID=7331
|
|There are some rather blatant errors in this article.   When this study
|few came out 2 years ago, the authors were claiming the asteroid
|was a "companion" of Earth, but now I see they're trying to make
|it more than it really is.
|
|The first blatant error: since
|Asteroid 3753 Cruithne does not orbit the Earth, it cannot be called
|the Earth's second moon.   The asteroid orbits the Sun in a
|separate elliptical orbit just like other asteroids.  See these
|diagrams of the asteroid's orbit:
|
|http://www.asteroid.yorku.ca/3753_5.gif
|
|Also, since the asteroid is in its own separate orbit and does not
|share Earth's orbit, it also cannot be called a trojan asteroid, which
|the authors of this article are claiming.  In all other cases of trojan
|asteroids such as with Jupiter and Mars, the trojan asteroids share the
|same orbit as the planet.  Asteroid 3753 Cruithe is not an Earth trojan.
|
|The only thing the article can accurately claim, is the asteroid is
|in orbital resonance with the Earth.  Also, this orbital resonance is
|tied in with the Earth's Lagrange points.  But again, since the asteroid
|does not share Earth's orbit, it is not a trojan asteroid.
|
|The authors also put a lot of emphasis on the horseshoe orbit, but leave
|out the critical fact that the horseshoe orbit of the asteroid only exists
|from an geocentric view (or as appeared from Earth).  You get a lot of
|strange looking orbit shapes from an Earth-viewing only perspective.
|From a heliocentric view (or from the Sun's perspective), which is what
|most people are familiar with, the orbit of the asteroid is a normal
|elliptical orbit around the Sun, and just happens
|to pass close enough to Earth to be in orbital resonance with the Earth.
|
|Again, the asteroid is not a second Moon of the Earth, nor is it a trojan
|asteroid, though authors would very much want it to be that way.
|Also, the people in the know, such as in the IAU, are very aware of the
|real facts on this asteroid.  The IAU is the official naming and
classification
|committee of solar system objects.  Asteroid 3753 Cruithe
|is not classified by the IAU as an Earth satellite or an Earth trojan.
|
|Ron Baalke
|
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