Pictures of the solar corona (5 pictures)

The extended outer atmosphere of the Sun is called the corona. It has a temperature of millions of degrees, but it is 10 billion times less dense than the atmosphere of the Earth at sea level.

The glow of the corona is a million times less bright than that of the photosphere, so it can only be seen when the disk of the Sun is blocked off in a total solar eclipse or by using a special instrument called a coronagraph (or coronameter) that artfically blocks the disk of the Sun so that it can image the regions surrounding the Sun.