3D shape, cartography, and geoid of Comet 67P C-G |
3D shape, cartography, and geoid of Comet 67P C-G |
Aug 6 2014, 02:11 PM
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#1
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Solar System Cartographer Group: Members Posts: 10227 Joined: 5-April 05 From: Canada Member No.: 227 |
Explorer 1 said:
"A 2D map of C-G seems like a tough order; the projection math alone..." Don't worry! If you can put a grid on the surface (as we have seen already), you can warp that grid into any map projection you like. Mapping will be no huge problem - in fact I expect they have a rough one already (I've been playing with one myself). Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PDF: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Aug 8 2014, 11:36 PM
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#2
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Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
Rotation rate is 12.7 hours. The circumference drawn by the 4km length of the comet ( a 2km radius ) is 12.6 km So very roughly - it's doing 1km/hr or 0.28m/sec. V^2/r is thus 0.000039 m/sec^2 Surface gravity is approximated as 10^-3 m/sec^2 3 orders of magnitude higher than the centripetal acceleration due to rotation. Hmm, according to the Wikipedia version, the escape velocity is estimated to 0.46 m/s, corresponding to about 0.33 m/s for a circular orbit. So I'd say within the current uncertainty, respecting the rotation, the resulting surface gravity at the parts most distant to the center of mass is about zero. A significantly more compact body with the same angular momentum would be torn apart. This opens a scenario almost opposing the contact binary approach, meaning head and body could have been broken apart already by centrifugal pseudo-force, and kept together by the stretched "neck", which would give the "rubber" duck metaphor more sense than originally anticipated. This way the inner of the comet would be exposed at the neck. Additional momentum could have been provided by impacts or by YORP. |
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Aug 9 2014, 12:08 AM
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#3
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Founder Group: Chairman Posts: 14434 Joined: 8-February 04 Member No.: 1 |
Hmm, according to the Wikipedia version, the escape velocity is estimated to 0.46 m/s, corresponding to about 0.33 m/s for a circular orbit. So I'd say within the current uncertainty, respecting the rotation, the resulting surface gravity at the parts most distant to the center of mass is about zero. No - the centripetal acceleration is 4 orders of magnitude less than the escape velocity. |
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