Sun's Atmosphere Hotter than Surface [VIDEO]

The Sun's outer atmosphere is hotter than its surface, and scientists have just pinned nanoflares as the reason behind this mysterious extra heat, according to a new study.

Nanoflares are a constant peppering of impulsive bursts of heating, none of which can be individually detected.

Even more surprising to scientists is that these observations stem from just six minutes of data from NASA's EUNIS mission. Short for Extreme Ultraviolet Normal Incidence Spectrograph, the EUNIS sounding rocket launched in April 2013, gathering data every 1.3 seconds to track the properties of material over a wide range of temperatures in the complex solar atmosphere.

The Sun's visible surface, called the photosphere, is some 6,000 Kelvins while the atmosphere regularly reaches temperatures which are 300 times as hot.

"That's a bit of a puzzle," Jeff Brosius, a space scientist at NASA's Goddard Space Flight Center in Maryland, said in the space agency's 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."

One theory behind this temperature difference is that a myriad of nanoflares could possibly heat up solar material in the atmosphere to temperatures of up to 10 million Kelvins. This material would cool very rapidly, producing ample solar material at the one to three million degrees regularly seen in the corona, or outer atmosphere.

However, the faint presence of that extremely hot material should remain, and the EUNIS team found just that. They spotted a faint emission line, where a wavelength of light corresponded to that 10 million degree material.

"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," Brosius added.

Brosius and other scientists plan to further explore the mechanism behind nanoflares and how they heat up the corona to such blistering temperatures.

The study's findings were published in The Astrophysical Journal on Aug. 1.

[Credit: NASA/Goddard/Duberstein]