Transit

Observe the 2012 transit of Venus across the sun captured as seen by the Solar Dynamics ObservatorySee all videos for this article

transit, in astronomy, the passage of a relatively small body across the disk of a larger body, usually a star or a planet, occulting only a very small area. Mercury and Venus periodically transit the Sun, and a moon may transit its planet. Extrasolar planets (e.g., HD 209458b) have been discovered when they perform a transit of their stars. Compare eclipse.