|MadSci Network: Astronomy|
Ryan, Thanks for the question. I can answer it, but in the process with just raise another. The Sun rotates because the material that it is made from already had some "rotation" built into it. The quantity that is used to keep track of rotation in changing situations is called angular momentum. The idea of angular momentum is that it is not just the amount of mass and the rate of rotation that is important, but also how spread out the mass is. Before the Sun formed, the material of the proto solar system was fairly spread out compared to how it is now. It probably took centuries or millenia for this cloud to make one revolution. As this material pulled together and became concentrated into the Sun and planets, it had to maintain its angular momentum. The mass stayed the same, so everything had to rotate faster. This is just like the situation where a spinning ice skater can spin more rapidly by pulling their arms in close to their axis of rotation. The Sun and almost all the planets all spin and/or rotate in the same direction, because they all came from the same spinning cloud of gas and dust. So why did the cloud that formed the Solar system have angular momentum? This is still an open question, but if you look up "solar system formation", or "stellar nurseries", or "nebula", you may have what you are looking for. Regards, Everett Rubel
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