Of course, if they do ever demote Pluto (and don't allow "Xena") we could crank it back up to 9 with our "Moon". If I remember correctly - if you observed our Moon's orbit from above or below the plane of the solar system - it would be a highly perturbed orbit - around the Sun. I.e. you wouldn't see "loops" in its orbit. But, instead you would see it "weaving in and out". So, I say to the IAU - give us our tenth planet or we'll take the Moon hostage. <g> Clear skies, Dale. -----Original Message----- From: utah-astronomy-bounces+dale.hooper=sdl.usu.edu@mailman.xmission.com [mailto:utah-astronomy-bounces+dale.hooper=sdl.usu.edu@mailman.xmission. com] On Behalf Of Joe Bauman Sent: Tuesday, August 02, 2005 1:52 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] planets - or not Very good point, Kim. When I was talking with my son, Sky, the other day he suggested the same definition for a planet, large enough that its gravity forms it into a sphere and in orbit around a star. The last part rules out moons that are big enough but are not planets. I think it's a fine definition. The question is, what is the lower limit for enough mass to create a sphere? And how perfect does the sphere have to be? (In a sense, Jupiter isn't a very good sphere -- it's oblate because it is so large and spins so fast and is so gaseous that it bulges at the belt).) -- Joe _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.utahastronomy.com