The Sun's core is millions of degrees, while the solar surface is a balmy 5800 kelvin. But travel to the Sun's outer atmosphere, the corona, and it heats up to millions of degrees again. The corona is a wispy plasma envelope extending millions of miles above the Sun's surface. Why the tenuous atmosphere above the sun is hotter than the actual surface has remained a mystery. One generic explanation has been that magnetic fields must be involved, but getting beyond this superficial understanding has required more detailed observations.