Henry,
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Sorry, this discussion belongs in your other thread.
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Anyhow, Accrete is the grandaddy of planetary formation simulation programs. Given a protoplanetary nebula of a specified composition, it forms a planetary system by accretion (hence the name) with a distribution of planetary types and orbits. It was written back in the '70s. Back then you needed a supercomputer to run it. These days, anybody can.
Right now, Celestia can't draw Stars reliably if they're more than 16KLY from the sun. With persistance from people like you, one can hope that this limitation eventually will be removed, hopefully sooner rather than later.