The most accurate measurements yet account for magnetic activity that gives the star a more oval appearance.
With its turbulent structure, tangled magnetic fields and a propensity to expel billion-ton clouds of charged particles, the sun makes it difficult to measure its exact shape.
Now researchers using a NASA spacecraft called RHESSI, the Reuven Ramaty High Energy Solar Spectroscopic Imager, have measured with unprecedented accuracy just how out-of-round the sun is.
The measurements reveal that the sun’s magnetic fields, already known to figure prominently in solar outbursts, also make the sun appear slightly more elongated, or flattened, during times of high solar activity. During the sun’s 11-year activity cycle, the magnetic activity and explosive nature of the star waxes and wanes.