Discovering the Sun's Mysteriously Hot Atmosphere

Something mysterious is going on at the Sun. In defiance of all logic, its atmosphere gets much, much hotter the farther it stretches from the Sun’s blazing surface.

Temperatures in the corona — the Sun’s outer atmosphere — spike to 3 million degrees Fahrenheit, while just 1,000 miles below, the underlying surface simmers at a balmy 10,000 F. How the Sun manages this feat is a mystery that dates back nearly 150 years, and remains one of the greatest unanswered questions in astrophysics. Scientists call it the coronal heating problem. Watch the video to learn how astronomers first discovered evidence for this mystery during an eclipse in the 1800s, and what scientists today think could explain it.