We now have 12 planets... give or take...

[David Farber <dave () farber net>]

Begin forwarded message:

From: Joseph Lorenzo Hall <joehall () gmail com>
Date: August 24, 2006 11:54:00 AM EDT
To: Dave Farber <dave () farber net>
Subject: We now have 12 planets... give or take...
Reply-To: joehall () pobox com

The International Astronomical Union has voted (and passed) a new
definition scheme as to what constitutes a "planet".

The Final IAU Resolution on the definition of "planet" ready for
voting. <http://www.spaceref.com/news/viewpr.html?pid=20674>

A "planet" is an object orbiting the Sun that is large enough to form
a rough sphere (when gravity balances pressure).  Any object orbiting
a planet is a satellite (unless the center of mass of their orbit is
outside the primary object, like Pluto and Charon, which are now both
dwarf planets).

(There's some speculation that the definition involved would make
Earth and Jupiter not actual planets because they haven't "cleared the
neighbourhood around its orbit" (Near-Earth Objects and Trojan
Asteroids respectively).)

What are the other three "planets" that have been added to the
traditional nine?  Well, Pluto's "moon" [Charon][1] is now a planet.
The asteroid [Ceres][2], which is large enough to be spherical and
orbits the Sun is now a planet.  Finally, a recently discovered large
and round object that is larger than Pluto, [UB313][3], is also a
planet. -Joe

[1]: http://en.wikipedia.org/wiki/Charon_%28moon%29
[2]: http://en.wikipedia.org/wiki/1_Ceres
[3]: http://en.wikipedia.org/wiki/2003_UB313


--
Joseph Lorenzo Hall
PhD Student, UC Berkeley, School of Information
<http://josephhall.org/>


--
Joseph Lorenzo Hall
PhD Student, UC Berkeley, School of Information
<http://josephhall.org/>


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