You might think that there is nothing hotter than the surface of the Sun, but there is: The atmosphere around the Sun is 300 times hotter. Scientists have determined that the Sun’s corona is heated by a succession of tiny explosions called nanoflares. These heating bursts can generate extreme temperatures -- as high as 18 million degrees Fahrenheit (10 million degrees Celsius).
"The explosions are called nanoflares because they have one-billionth the energy of a regular flare," says Jim Klimchuk, a solar scientist at NASA's Goddard Space Flight Center. "Each packs the wallop of a 10 megaton hydrogen bomb. Millions of them are going off every second across the Sun, and collectively they heat the corona."
A hot spot in the universe:
- The Sun's surface is searingly hot at 10,340 degrees Fahrenheit (5,730 degrees C). About three quarters of the Sun's mass consists of hydrogen. The rest is mostly helium.
- The Sun is the star at the center of our solar system. It’s a nearly perfect sphere of hot plasma.
- The Sun is considered middle-aged and has not changed significantly for more than four billion years. It is expected to remain fairly stable for another five billion years or so.