The fact that the sun is hot should not be news to a single person. The sun’s surface is about 10,000 degrees Fahrenheit, which seems toasty enough. But surrounding the sun is an atmosphere of sorts called the corona. This envelope of superheated gas — plasma, actually — measures more than 3 million degrees. And scientists are still trying to figure out how this outer layer is so much hotter than what lies beneath it.
The part that confuses scientists is quite simple: Since the sun’s heat source (which they do understand) is at its core, it should more or less cool as you move farther away from the center. But this isn’t what they observe. So, even with the sun right there, it’s not enough to explain how the corona is so much hotter than other layers. And before we move on, it’s probably a good reminder that heat is actually a measurement of how fast atoms are moving. So solar physicists are mostly looking for ways to accelerate this material, in a way that somehow happens only in the sizzling corona.
