By Laura Shin
Posting in Government
Given the fact that it rotates, you would expect the sun to have a slightly flattened shape. That's why its nearly perfect roundness surprised scientists.
The sun, like all objects that rotate, should have a slightly flattened shape. And because it not only rotates but is made of gases, it is even more likely to be a bit more flattened than a perfectly round object.
And that's why scientists are amazed: The sun is just about perfectly round.
It's so round that if we shrank it down to a beach ball size a meter in diameter, the difference in its vertical diameter versus its horizontal diameter would be less than the width of a human hair. In fact, its East-West diameter would be a mere 17-millionths of a meter larger than its North-South diameter.
The finding by Jeff Kuhn and Isabelle Scholl at the Institute for Astronomy, University of Hawaii at Manoa, Rock Bush of Stanford University, and Marcelo Emilio of Universidade Estadual de Ponta Grossa, Brazil, was published in Science Express.
Kuhn said in a press release, "For years we've believed our fluctuating measurements were telling us that the sun varies, but these new results say something different. While just about everything else in the sun changes along with its 11-year sunspot cycle, the shape doesn't."
The researchers also found this flattening is smaller than what you'd predict given the sun's surface rotation. This suggests that other subsurface forces, like solar magnetism or turbulence, are preventing flattening and instead supporting the round shape.
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via: press release
photo: Image of the sun taken by the Solar Dynamics Observatory. (NASA)
Aug 29, 2012
As I understand it, the sun has so much mass that the force of gravity was enough to cause fusion to start, which pushes back and balances it out, keeping the sun from collapsing further. Wouldn't the forces of this interplay alone be enough to overwhelm the distorting effects of the sun's rotation? Couldn't it be that simple?
They surely would have factored those forces into their calculations; and they act uniformly in all directions. What this suggests is that there some force which is not uniform acting in opposition to the horizontal expansion centrifugal force tends to produce. My bet is on magnetism. Sunspots evidence a high level of magnetism - and they occur near the solar equator, not at the poles. It's theorized that this magnetism hinders the upwelling of hot gas from the core, making the sunspots cooler than the surrounding surface (which is why they appear darker). I would guess this also shrinks the solar equatorial region, counteracting centrifugal force. It sounds good, anyway. :-)