Total solar eclipse Computerenhanced image of the Suns corona seen at the moment of totality during a total solar eclipse The corona is a cloud of lowdensity plasma hot ions surrounding the Sun Normally it is not visible being obscured by the brightness of the Suns visible surface but it is revealed during a total solar eclipse which occurs when the Moon blocks the light from the rest of the Sun The moons surface can be seen due to light reflecting off the surface of the earth a phenomenon known as earthshine This moment of totality lasts for only a few minutes Total solar eclipses usually occur less than once a year and can only be seen from a small area of the Earths surface
