The sun’s surface is hot, sure — almost 10,000 degrees Fahrenheit
— but the solar atmosphere, or corona, is somehow 4 million
degrees. What gives? In April, scientists announced the main
reason: small bursts of magnetic
energy called nanoflares, which
temporarily heat pockets of gas to
20 million degrees.
“The sun’s surface is much like
a pot of hot oil on the stove,”
says NASA solar scientist James
Klimchuk. “Hot oil rises, spreads
out horizontally, cools and falls
back down to the bottom of
the pot, only to rise again.”
That constant movement can
twist and tangle the magnetic
fields that thread through the
sun and extend into the corona.
Eventually, like a rubber band, they reach a point where they snap. Scientists
had theorized this would cause a nanoflare.