Here's why:
* The corona is the outermost layer of the sun's atmosphere. It's incredibly hot and thin, extending millions of kilometers into space.
* The corona is normally too faint to see because it's overwhelmed by the intense light from the sun's photosphere (the visible surface).
* During a total solar eclipse, the moon completely blocks out the photosphere. This allows us to see the faint corona, which appears as a pearly white halo around the eclipsed sun.
