The Sun’s corona, or outer layer of atmosphere, can only be seen during a solar eclipse.
At other times, the brightness of the Sun makes the corona disappear from sight, just as the Sun’s light makes it impossible to see stars in the daytime.
Astronomers artificially block the Sun’s surface with special equipment, so as not to damage their eyes, in order to study the corona.
The corona can extend more than 1 million miles (1.609 million km) around the Sun.
Its shape changes with the appearance of sunspots.
When the sunspots are at the height of their cycle, the corona is almost circular.
At the end of the sunspot cycle, the corona appears stretched out, with huge streams of gases coming out.
The corona is always thinnest at the Sun’s northern and southern magnetic poles.