News FocusAstronomy

Why Is the Sun's Corona So Hot?

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Science  01 Jun 2012:
Vol. 336, Issue 6085, pp. 1099
DOI: 10.1126/science.336.6085.1099

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Summary

Yes, the sun is hot—really hot. It's 16 million kelvin at its fusion-fueled core, cooling, as the second law of thermodynamics requires, to a still-blistering 5780 K at its visible surface. But for the better part of a century, solar physicists have been mystified by the sun's ability to reheat its corona, the encircling wispy crown of light that emerges from the glare during a total solar eclipse. There, temperatures again soar to 1 million K and more. How would heat dissipating from the core out beyond the surface abruptly punch temperatures up by a factor of 200 and more?