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Physics, Astronomy & Cosmology / Re: Could a planet be orbited by another planet instead of a moon?
« on: 03/12/2013 10:38:09 »Jupiter would be a bright point in the sky, easily visible before sunrise or after sunset (depending on whether Earth was at L4 or L5).Thank you, Kind of what I wanted to hear
However, if you placed the Earth at the orbit of Io, Jupiter would be a giant sky-filling orb (I calculate that Jupiter would be 19 degrees across as seen from Io, hundreds of times bigger than the Moon as seen from Earth). If Earth were tidally locked to Jupiter, the day would be a rather tiring 42 hours - but with a natural siesta every noon.
I am interested in that Earth being Giants moon idea. Often there are imagined Earth like planets as being moon of some Gas Giant. To have night/day cycle on both sides of that moon it has to orbit the way that it does not get behind Giant at any time or the whole planet would be in complete darkness for some time and one part would never see the sun. I was trying to find out 3d image of Ios path around Jupiter but did not found. It has to orbit in very special way kind of like our moon that it can take sun on both sides during the cycle of day. Or how that work in order to have day and night on both sides?