Knight of Clear Skies wrote:Something I'd be interested in learning more about, do we have any idea why Vega rotates so rapidly? According to the
wiki article it is highly elongated and if it was spinning 14% faster it would break up due to centrifugal forces.
![Image](https://upload.wikimedia.org/wikipedia/commons/thumb/c/c8/Size_Vega.png/300px-Size_Vega.png)
(Polar view of Vega compared to the Sun.)
Actually if those views were polar both stars would be perfectly round. The image should be labeled as an equatorial view, since the rotational bulging is greatest at the equator.
Is Vega's rotation rate particularly high for a star of its type/age, and does it tell us anything about its formation history? (Am I in fact asking the wrong question, should it be "Why does the Sun rotate so slowly?") Can anyone shed any light on this please?
Stars form from moving, somewhat turbulent clouds of interstellar gas and dust. With all the buffeting about these clouds receive from the radiation from the stars around them parts of the gravitationally collapsing cloud will be moving in differing directions. Most (perhaps all) of this interstellar material will not just fall in a straight line down to the growing protostar, but it will spiral in as it falls because the momentum of its previous history is conserved. The new star ends up spinning with whatever average rotational orientation was possessed by the sum of all the material that falls into it.
How fast it spins is at first determined by (1) how much average angular momentum the protostar received from the cloud it collapsed from, and (2) the final size the star collapses down to. More massive stars like Vega must spin faster because they formed from larger, more extensive clouds with more angular momentum than the cloud our sun formed from.
Nice question, Knight of Clear Skies.
Bruce
Just as zero is not equal to infinity, everything coming from nothing is illogical.