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The sun is rounder than we previously thought. No, really

A new two-year study – monitoring suspected changes in the star’s shape – reveal a more rounded sphere than expected.

Image: apollo1981 via Flickr

THE SUN is rounder than astronomers had previously believed.

That startling (no, really) conclusion is the result of an intensive two-year study of the sun’s movements, which were previously thought to give it a slightly less defined shape.

The shape of our closest star is more than just an academic puzzle: even a minute shift in its shape can have a distinct effect on weather patterns on Earth, as well as resulting in solar flares that can (and sometimes do) disrupt wireless communications on Earth.

The sun has an 11-year sunspot cycle, which had led previous opinions to agree that while the sun was evidently spherical in shape, its exact shape fluctuated in line with the variance in its sun spots.

It was also thought that the star’s 28-day rotation cycle meant it would be have slight bulges around its equator, as the Earth and all other planets do.

Having examined a series of high-resolution images taken between 2010 and 2012, however, astronomers have concluded that while the sun does have a equatorial bulge, its overall shape remains remarkably stable – and the sun is, in fact, the most perfectly round thing known to man.

If the star was shrunken so that its diameter was only one metre, the difference in the gap between its north-south diameter and its equatorial one is a mere 17 millionths of a metre – far less than the width of a strand of human hair.

“So far, just about anything we measure with sufficient accuracy about the sun ends up varying with the 11-year sunspot rhythm,” the study’s lead author Jeffrey Kuhn, from the University of Hawaii, told Space.com.

While there were “literally tens” of measurements of the sun’s actual dimensions, Kuhn said, most of them were incompatible – largely because of how minute observations could be disrupted and skewed by small particles in the Earth’s atmosphere.

That’s no problem for these conclusions, as the images used to reach them were taken by a Solar Dynamics Observatory satellite which is already in orbit above our planet.

“The sun is very, very round, so it’s difficult to measure any deviations in that roundness,” Kuhn added to Latinospost.com.

“It’s only been in the last few years that we’ve been able to make decent shape observations.”

Read: Life on Mars: how close are we to living in space?

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Gavan Reilly

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