Sun’s almost perfectly round shape baffles scientists


Share post:

The sun is nearly the roundest object ever measured. If scaled to the size of a beach ball, it would be so round that the difference between the widest and narrow diameters would be much less than the width of a human hair. 

Image of the sun taken by the Solar Dynamics Observatory [Credit: NASA]

The sun rotates every 28 days, and because it doesn’t have a solid surface, it should be slightly flattened. This tiny flattening has been studied with many instruments for almost 50 years to learn about the sun’s rotation, especially the rotation below its surface, which we can’t see directly. 

Now Jeff Kuhn and Isabelle Scholl (Institute for Astronomy, University of Hawaii at Manoa), Rock Bush (Stanford University), and Marcelo Emilio (Universidade Estadual de Ponta Grossa, Brazil) have used the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory satellite to obtain what they believe is the definitive — and baffling — answer. 

Because there is no atmosphere in space to distort the solar image, they were able to use HMI’s exquisite image sensitivity to measure the solar shape with unprecedented accuracy. 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. 

They also found that the solar flattening is remarkably constant over time and too small to agree with that predicted from its surface rotation. This suggests that other subsurface forces, like solar magnetism or turbulence, may be a more powerful influence than expected. 

Kuhn, the team leader and first author of an article published Aug. 16 in Science Express, said, “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.” 

This work was supported by NASA grants to Stanford University and the University of Hawaii. 

More information about SDO: 

Source: University of Hawaii Institute for Astronomy [August 16, 2012]



Related articles

Climate shift could leave some marine species homeless

Rising temperatures will force many species of animals and plants to move to other regions and could leave...

Ephesus ahead of its time

Jesus Christ's disciples St Paul and St John the Evangelist both walked along this wide street in Ephesus....

Mysterious quasar sequence explained

Quasars are supermassive black holes that live at the center of distant massive galaxies. They shine as the...

Narrative of the body, with a nasty twist

Humans crave comfort. Sadly, comfort isn’t always good for us. That’s one of the conclusions of Harvard evolutionary...

Antarctic penguin colony repeatedly decimated by volcanic eruptions

One of the largest colonies of gentoo penguins in Antarctica was decimated by volcanic eruptions several times during...

New fossilized fox species found in South Africa

Researchers from Wits University, the University of Johannesburg and international scientists announced on January 22, 2012, the discovery...

Volcanic aerosols, not pollutants, tamped down recent Earth warming

A team led by the University of Colorado Boulder looking for clues about why Earth did not warm...

Dense molecular gas disks drive the growth of supermassive black holes

A joint team of University of Tokyo researchers and their collaborators, using ALMA and other telescopes that utilize...