Total solar eclipse. Visible surface of the Sun (upper left) shining along the edge of the Moon as totality approaches during a total solar eclipse. The last glimpse of the Sun at this point often shines through the valleys at that point on the Moon, giving rise to the phenomenon known as Bailey's beads. Prominences (red) are seen either side of this Bailey's bead. As this last part of the Sun is covered by the Moon, the corona (the Sun's atmosphere) will become visible. The 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 Earth's surface. Photographed from Turkey on 29 March 2006.