Does the Sun rotate?

  • The planets rotate as an after effect of their creation, the dust clouds that compressed span as they did so and the inertia has kept it rotating ever since.

    It's fairly easy to prove that planetary bodies are rotating just by watching their features move across their respective horizons.

    This seems less easy to discern for amateur astronomers in the case of the sun though.

    Does the Sun also rotate as a by-product of it's creation? What evidence is there to support this? Does the sun have any discerning features that make it evident it is rotating?

    Why did Galileo bother?

  • Manishearth

    Manishearth Correct answer

    9 years ago


    It does not rotate uniformly though, different portions have a different angular velocity (as a body made of plasma, it can get away with this).

    Measuring this in theory is pretty easy, we just need to track the motion of the sunspots. This isn't as simple as calculating the changes in relative positions of the sunspots, though, as the Earth is rotating and revolving, which makes the calculations harder. This measurement can be done using the celestial sphere (the field of stars that we see) as a "fixed" reference point and seeing how the Earth and the sunspots move relative to that.

    Almost everything in the universe rotates/revolves, at least a little bit, because angular momentum is hard to get rid of. It can be transferred from body to body, but for a body to end up with zero angular momentum, it needs to meet another body with the exact same angular momentum and collide with it in a particular way. Given that this is pretty rare, all celestial bodies rotate.

    In addition to that, a non rotating body that is revolving will eventually start spinning due to tidal forces.

    So if the sun were not to rotate, it would start doing so (albeit it seems extremely slowly) thanks to its revolution around the Milky Way?

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Content dated before 7/24/2021 11:53 AM