Shooting a million miles or more out into the hard, cold vacuum of space, this fiery halo is one of the wonders of the universe. Whipped into gigantic swirls by the Sun's ferocious magnetic fields, the shell of super-hot gas is as beautiful as it is dangerous. It's called a corona and can't normally be seen because of the brightness of the Sun, a broiling sea of hydrogen gas at 10,000c. But during a solar eclipse, the Moon blocks out the Sun and the corona is spectacularly revealed.As hot as the Sun is, the corona is 200 times hotter - more than a million degrees celsius. Why this should be is a mystery. Some believe it is the result of a form of heating called induction - the same thing that powers hi-tech cooking hobs. As well as being very hot, the ionised gas of the corona (called plasma) has a superthin consistency. It is less than a billionth of the density of the hydrogen that makes up the main ball of the Sun. The odd result of this is that if, by some magic, you were to touch the corona, you would freeze rather than fry.
Despite its thinness, the corona can pack a deadly punch. Occasionally, the Sun's surface erupts in a solar quake, a paroxysm of gigantic storms and flares. Sometimes these are powerful enough to eject vast blobs of corona gas into space at millions of miles per hour. (Daily Mail)
