Transit of Venus

Astronomical transit of Venus across the Sun

A transit of Venus takes place when Venus passes directly between the Sun and the Earth (or any other superior planet), becoming visible against (and hence obscuring a small portion of) the solar disk. During a transit, Venus is visible as a small black circle moving across the face of the Sun. Transits of Venus reoccur periodically.

From Wikipedia, under CC BY-SA. More on occurri.