C
CalliArcale
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This is a topic that has come up frequently lately, so it is obviously of great interest. It can't be properly dealt with in most of the other threads without stomping on the topics of those other threads, so I'm starting a fresh thread where we can really get down to business on the subject.<br /><br />The formation of solar systems.<br /><br />The most popular model nowadays is accretion. There are several flavors of this model; it is not entirely accurate to say that because one has issues with one of them, they must all be wrong, and it's important to know this. I'm hopeful that one of our resident astronomy students (perhaps Saiph) can help outline various models in more detail, because it's not something I know a lot about myself. I only understand it on a high level. And of course I don't get the EU version at all, so perhaps someone who is well-versed in that can give a brief summary of that one too.<br /><br />The basic gist of accretion, in all its flavors, is that particles in a sufficiently dense cloud will randomly encounter one another. Some of them will stick together, at first probably through nuclear forces or static electricity, but once there are enough, they'll start to capture other particles through gravity. As the clump of particles grows, it becomes stronger and better able to both capture and retain particles. Given enough time and enough particles, it could become a planet, or even a star. When a star forms, it begins to put out a powerful solar wind. It is expected that this blasts away a great deal of the remaining material, slowing or even halting planet formation. Our own solar system has few volatiles in the inner solar system (with Earth's vast water oceans being a notable and curious exception), and it has long been presumed that the ignition of the Sun had something to do with that. However, the discovery of Hot Jupiters poses a potential problem for that. (So does the Earth itself; one must explain where the oceans came from <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em> -- The Tenth Doctor, "Blink"</font></p> </div>