The fact that the sun’s outer atmosphere is hotter than its actual surface has puzzled scientists for a while now. The sun’s visible surface is called the photosphere. The photosphere is some 6,000 Kelvins in temperature. The outer atmosphere or the corona should be cooler. However the corona regularly reaches temperatures which are 300 times hotter than the photosphere.

A number of theories have been put forward, but researchers feel that the actual reason has now been uncovered. This reason is the Nanoflares! Nanoflares are a constant peppering of impulsive bursts of heating which occur on the sun, none of which can be individually detected.

NASA’s Solar Dynamics Observatory took pictures of the Sun in the month of April which showed Solar Nanoflares in the form of bright loops. These are the phenomenon that cause the sun’s surface to stay cooler than the sun’s atmosphere.  These pictures are from the EUNIS mission which was launched to study the particularly active parts of the sun.

While researchers are not giving up on other theories altogether, this set of photographic evidence has certainly given the nanoflare theory a major boost. It will be interesting to see what else the EUNIS mission manages to uncover for NASA scientists to study during this science project.