Venus The Planet
Venus, second planet from the Sun and sixth in the solar system in size and mass. No planet approaches closer to Earth than Venus; at its nearest it is the closest large body to Earth other than the Moon. Because Venus’s orbit is nearer the Sun than Earth’s, the planet is always roughly in the same direction in the sky as the Sun and can be seen only in the hours near sunrise or sunset. When it is visible, it is the most brilliant planet in the sky. Venus is designated by the symbol ♀.

Venus was one of the five planets—along with Mercury, Mars, Jupiter, and Saturn—known in ancient times, and its motions were observed and studied for centuries prior to the invention of advanced astronomical instruments. Its appearances were recorded by the Babylonians, who equated it with the goddess Ishtar, about 3000 bce, and it also is mentioned prominently in the astronomical records of other ancient civilizations, including those of China, Central America, Egypt, and Greece. Like the planet Mercury, Venus was known in ancient Greece by two different names—Phosphorus (see Lucifer) when it appeared as a morning star and Hesperus when it appeared as an evening star. Its modern name comes from the Roman goddess of love and beauty (the Greek equivalent being Aphrodite), perhaps because of the planet’s luminous jewel-like appearance.

Venus has been called Earth’s twin because of the similarities in their masses, sizes, and densities and their similar relative locations in the solar system. Because they presumably formed in the solar nebula from the same kind of rocky planetary building blocks, they also likely have similar overall chemical compositions. Early telescopic observations of the planet revealed a perpetual veil of clouds, suggestive of a substantial atmosphere and leading to popular speculation that Venus was a warm, wet world, perhaps similar to Earth during its prehistoric age of swampy carboniferous forests and abundant life. Scientists now know, however, that Venus and Earth have evolved surface conditions that could hardly be more different. Venus is extremely hot, dry, and in other ways so forbidding that it is improbable that life as it is understood on Earth could have developed there. One of scientists’ major goals in studying Venus is to understand how its harsh conditions came about, which may hold important lessons about the causes of environmental change on Earth.

Planetary Data For Venus

Mean distance from Sun  108,209,475 km (0.72 AU) 

Eccentricity of orbit 0.007 

Inclination of orbit to ecliptic 3.4°

Venusian year (sidereal period of revolution) 224.7 

Earth days maximum visual magnitude −4.6 

Mean synodic period* 584 Earth days 

Mean orbital velocity 35 km/sec 

Radius (mean) 6,051.8 km 

Surface area 4.6 × 108 km2Mass 4.87 × 1024 kg  

Mean density 5.24 g/cm3

Mean surface gravity 887 cm/sec2

Escape velocity 10.4 km/sec

Rotation period (Venusian sidereal day) 243 Earth days (retrograde)             

Venusian mean solar day 116.8 Earth days 

Inclination of equator to orbit 177.3°

Atmospheric composition carbon dioxide  96%; molecular nitrogen,             

3.5%;   water, 0.02%; trace quantities of carbon 

monoxide, molecular oxygen, carbon

sulfur  dioxide, hydrogen chloride, and other gases

Mean surface temperature 737 K (867 °F, 464 °C)

Surface pressure at mean radius 95 bars

Mean visible cloud temperature about 230 K (−46 °F, −43 °C) 

Number of known moons none

Basic Astronomical Data

Viewed through a telescope, Venus presents a brilliant yellow-white, essentially featureless face to the observer. Its obscured appearance results from the surface of the planet being hidden from sight by a continuous and permanent cover of clouds. Features in the clouds are difficult to see in visible light. When observed at ultraviolet wavelengths, the clouds exhibit distinctive dark markings, with complex swirling patterns near the equator and global-scale bright and dark bands that are V-shaped and open toward the west. Because of the all-enveloping clouds, little was known about Venus’s surface, atmosphere, and evolution before the early 1960s, when the first radar observations were undertaken and spacecraft made the first flybys of the planet.