January 26th, 2010

one atmosphere around multiple planets

Hi!

I'm working on the world for a science fiction story and was wondering if this was possible. Basically, I thought there are two groups of planets, each with only one or two, possibly three planets. They're separated by something like an asteroid belt. I was wondering if it's possible for all of these planets and the asteroids to be inside one atmosphere.

I did some searching with terms like "atmosphere" and "planets", but I didn't find anything specific to this idea. Wikipedia says that Earth's atmosphere is retained by its gravity. So if the atmosphere that's surrounding those other planets were retained by a mutual gravity source, would it be possible for them to all have the same atmosphere? I was thinking that if they did have the same atmosphere, they would orbit their sun as a single unit, too, never moving away from each other.

I admit that I'm new to science fiction world building... I'm more of a fantasy writer. I'm also not very good at science in general. So if I'm totally off or something, I apologize in advance. Any insight on this idea would be most appreciated. :D

Edit: Wow, thanks for all the info! Looks like this idea won't work, eh? Then I have but one more question regarding this idea in general... what if the planets were contained in some kind of large glass structure? Or any kind of structure, really... Honestly, it sounds like it might be more unlikely than the first idea. If it really is completely unrealistic scientifically, I'll either change the story around to be a little more fantasy or I'll just let the planets be normal. The story itself doesn't depend on this setting, so I'm free to mess with it. Thanks again for all the input!