Why the Sun's Corona is 300 Times Hotter Than Its Surface: Nanoflares (VIDEO)

First Posted: Aug 04, 2014 06:58 AM EDT

You'd think that the sun's surface would be hotter than its outer atmosphere, but that's not the case. In fact, it's a phenomenon that has puzzled scientists for decades. Now, they may have the answer; new observations reveal that it may have something to do with nanoflares.

Nanoflares are a constant peppering of impulsive bursts of heating, none of which can technically be detected. Current theory states that these tiny flares could be powering the heating in the sun's outer atmosphere. Certainly, something has to be powering it. While the sun's surface is a whopping 3,000 Kelvins, the corona temperatures are almost 300 times as hot.

"That's a bit of a puzzle," said Jeff Brosius, space scientist at NASA's Goddard Space Flight Center, in a news release. "Things usually get cooler farther away from a hot source. When you're roasting a marshmallow you move it closer to the fire to cook it, not farther away."

Now scientists have used data from the EUNIS mission in order to learn a bit more about the sun's unusual pattern of heating. Standing for Extreme Ultraviolet Normal Incidence Spectrograph, the EUNIS mission gathers a new snapshot of data every 1.3 seconds in order to track the properties of material over a wide range of temperatures in the solar atmosphere. It was tuned into a range of wavelengths useful for spotting temperatures of 10 million Kelvin, which are temperatures that are a signature of nanoflares.

So what did they find? It turns out EUNIS was able to pick up a wavelength of light corresponding to that 10 million degree material.

"The fact that we were able to resolve this emission line so clearly from its neighbors is what makes spectroscopists like me stay awake at night with excitement," said Brosius. "This weak line observed over such a large fraction of an active region really gives us the strongest evidence yet for the presence of nanoflares."

The findings reveal a bit more about why the sun's corona is so much hotter than its surface. It's very possible, with this new data as evidence, that nanoflares are to blame.

The findings are published in The Astrophysical Journal.

Want to learn more? Check out the video below, courtesy of YouTube.

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