A transit of Venus takes place when Venus passes directly between the Sun and the Earth, becoming visible against the solar disk. During a transit, Venus can be seen as a small black circle moving across the face of the Sun.
William Richard Lavender, Jeremiah Horrocks (1618–1641) (1903), Astley Hall Museum and Art Gallery
Diagram from David Rittenhouse's observations of the 1769 transit of Venus
Image: NASA's SDO Satellite Captures First Image of 2012 Venus Transit (Full Disc)
Image: SDO's Ultra high Definition View of 2012 Venus Transit (171 Angstrom Full Disc)
Venus is the second planet from the Sun. It is a terrestrial planet and is the closest in mass and size to its orbital neighbour Earth. Venus is notable for having the densest atmosphere of the terrestrial planets, composed mostly of carbon dioxide with a thick, global sulfuric acid cloud cover. At the surface it has a mean temperature of 737 K and a pressure of 92 times that of Earth's at sea level. These extreme conditions compress carbon dioxide into a supercritical state close to Venus's surface.
True colour image of Venus, as captured by MESSENGER. A global layer of bright sulfuric acid clouds permanently obscures the Venusian surface.
Venus to scale among the terrestrial planets of the Solar System, which are arranged by the order of their Inner Solar System orbits outward from the Sun (from left: Mercury, Venus, Earth and Mars)
Surface of Venus as seen by Venera 13.
Radar mosaic of two 65 km (40 mi) wide (and less than 1 km (0.62 mi) high) pancake domes in Venus's Eistla region
