Just as the Moon passes in front of the last
part of the Sun's disk, the thin arc of light breaks
into a series of bright points of light. This is
because the surface of the Moon is not completely
smooth; there are mountains, valleys and craters.
For a brief time, the Sun's light is blocked
by the lunar mountains, but it is able to graze
through the valleys producing small beads of light.
Baily's Beads are named after the British astronomer
Francis Baily (1774 -1844).