Thanks for the clarification Chuck. -----Original Message----- From: Chuck Hards [mailto:chuckhards@yahoo.com] Sent: Monday, January 05, 2004 9:33 AM To: Utah Astronomy Subject: RE: [Utah-astronomy] Re: Comet picture Hi Kim: --- Kim Hyatt <khyatt@smithlayton.com> wrote:
Regarding the comment, "things that small should not be spherical": I understand that the mass is not sufficient to compel a spherical geometry, but why shouldn't they be spherical? Isn't a spherical shape as likely as any other shape? Anyone have a thought?
A spherical (or more precisely, spheroidal) shape is quite possible, but statistically very unlikely for a small object. I think too since activity on cometary surfaces isn't thought to be uniform over the entire surface, the comet's shape should become even more "random" over time, and I think this is what was implied. Not an outright rejection of the possibility of a spheroidal shape, but the chances are very, very slim. C. __________________________________ Do you Yahoo!? Find out what made the Top Yahoo! Searches of 2003 http://search.yahoo.com/top2003 _______________________________________________ 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
I the case of a comet I think that a sheroidal shape would be the very likely. A comet is basically a large collection of dust and ice. When the comets first form I would think they would more oddly shaped, but after numerous passes by the sun the outer parts would burn off. Since the nucleus is rotating I would expect the result would be closer to a sphere. I would also expect the surface to to be pocked from the erosion too. There are also many factors to consider in the process too. Like how much rock vs. ice is there? I would think the more ice there is the more likely it would be to a spheroid too. If it's more rocky, like an asteroid, the I would expect it be more oddly shaped. Who's to say, maybe many of the asteroids were once comets, but just had all the ice bured off. Ken -----Original Message----- From: utah-astronomy-bounces+killerken=killerken.com@mailman.xmission.com [mailto:utah-astronomy-bounces+killerken=killerken.com@mailman.xmission. com] On Behalf Of Kim Hyatt Sent: Monday, January 05, 2004 9:36 AM To: 'Utah Astronomy' Subject: RE: [Utah-astronomy] Re: Comet picture Thanks for the clarification Chuck. -----Original Message----- From: Chuck Hards [mailto:chuckhards@yahoo.com] Sent: Monday, January 05, 2004 9:33 AM To: Utah Astronomy Subject: RE: [Utah-astronomy] Re: Comet picture Hi Kim: --- Kim Hyatt <khyatt@smithlayton.com> wrote:
Regarding the comment, "things that small should not be spherical": I understand that the mass is not sufficient to compel a spherical geometry, but why shouldn't they be spherical? Isn't a spherical shape as likely as any other shape? Anyone have a thought?
A spherical (or more precisely, spheroidal) shape is quite possible, but statistically very unlikely for a small object. I think too since activity on cometary surfaces isn't thought to be uniform over the entire surface, the comet's shape should become even more "random" over time, and I think this is what was implied. Not an outright rejection of the possibility of a spheroidal shape, but the chances are very, very slim. C. __________________________________ Do you Yahoo!? Find out what made the Top Yahoo! Searches of 2003 http://search.yahoo.com/top2003 _______________________________________________ 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 _______________________________________________ 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
Ken, the shape of a celestial body depends solely on mass above a certain point, be that body made of ice, rock, or gas (even dark matter appears to be distributed spherically around galaxies). If the mass is below the "spheroidal threshold", then of course anything goes. Spin can also flatten a spheroid into an oblate shape, but it's still basically a spheroid. Not all comets rotate for even solar illumination, either. Some may have poles or portions (canyons, crevasses) that never see daylight. Different materials (exotic & water ices) will sublimate at different rates. Too, there is some evidence of venting as a source of some cometary ejecta. As far as I know, the only other comet nucleus we have an approximate shape for is Halley, and isn't it potato-shaped, IIRC? I agree with the scientists in that below a certain size, "roundness" gets progressively less likely, but not outright impossible. C. --- Ken Warner <KillerKen@killerken.com> wrote:
I the case of a comet I think that a sheroidal shape would be the very likely.
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participants (3)
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Chuck Hards -
Ken Warner -
Kim Hyatt