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)
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