transit

A transit is an astronomical body crossing between an observer and an astronomical body. Examples are transiting planets, such as Venus transiting across the Sun, any solar system planet crossing in front of a star, or an extra-solar planet crossing in front of its own star.

Transits are useful for a number of types of measurements and studies. Transits of moons in front of Jupiter and Saturn have yielded useful data.

The transit method, of detecting the magnitude variation of stars due to periodic transits, is one method of detecting exoplanets and is also useful for followup studies of planets discovered by other means.