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A small, polar-orbiting moon
In article , Jake
McGuire wrote: With close flybys in 3-body systems you can either eject or capture something, but that's not the situation you're describing. If Cynthia originally had a sister, a double asteroid like Hermes was just found to be, then you have a three-body system that might allow capture. It would take the same hand-of-god that placed Luna at just the right size and distance to give us nice solar eclipses, but it's possible. Especially with an aerobrake to bleed off some energy, then the second component circularizes Cynthia's orbit before being flung into the utterdark. (A single asteroid aerobraking gives an orbit that passes inside the atmosphere on subsequent passes, which quickly leads to lithocapture and a nice iridium layer for the next intelligent species to find.) Of course, the protagonist realizes this after single-handedly recapitulating the works of Galileo, Newton, Halley etc. from our time line to develop orbital mechanics, Percival Lowell to find the cast off sister, Shoemaker to discover that it will hit Earth in 3 years, Goddard, Tsiolkovskii and Korolev to build a rocket, Oppenheimer and the gang for the payload, and Bruce Willis to get the box office. Bogen: Luna will give off more light in total because it's larger but Cynthia is much closer so each solid angle measure (steradian?) should be brighter. I think Cynthia will lokk like a brighter, fast moving Venus. No, brightness per steradian depends on illumination (how far from the Sun it is--the same as the Moon is, plus a bit of Earthshine) and how reflective it is, but not on how far away it is. (The inverse square law, an approximation in this case, comes entirely from the solid angle shrinking with distance.) That's why a tree nearby doesn't burn your eyes out while a tree-covered distant mountain is other than black. -- David M. Palmer (formerly @clark.net, @ematic.com) |
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