The discovery that our Sun is almost a perfect sphere comes as somewhat of a shock to scientists, who have conducted precise measurements of its dimensions.
This is surprising news to scientists who have always expected our nearest star to bulge slightly at its equator.
The sun rotates every 28 days, and because it doesn’t have a solid surface, it should be slightly flattened.
Now, using the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory satellite a team led by the University of Hawaii’s Dr Jeffrey Kuhn has made a startling discovery.
After obtaining the first precise measurement of the sun’s equatorial bulge, scientists noticed that the results were much different that they expected.
“We were shocked,” says Kuhn. The sun doesn’t bulge much at all.
It is 1.4m kilometres across, but the difference between its diameter at the equator and between the poles is only 10 kilometres.
The results indicate that if the Sun were shrunk to a ball one meter in diameter, its equatorial diameter would be only 17 millionths of a meter larger than the diameter through its North-South pole, which is its rotation axis.
The astronomers also found that the solar flattening is remarkably constant over time and too small to agree with that predicted from its surface rotation.
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