Venus, Second major planet from the Sun. Named for the Roman goddess, Venus is, after the Moon, the most brilliant natural object in the night sky. Venus comes closer to Earth—about 26 million mi (42 million km)—than any other planet. Its orbit around the Sun is nearly circular at a distance of about 67 million mi (108 million km) and takes 225 days; its rotation, in retrograde motion, takes even longer (243 days). As viewed from Earth, Venus undergoes phase changes similar to the Moon’s, going through one cycle of phases in 584 days. It is seen only near sunrise or sunset and has long been known as both the morning star and the evening star. Venus is a near twin of Earth in size and mass but is completely enveloped by thick clouds of concentrated sulfuric acid droplets. Its surface gravity is about 90% that of Earth. Its atmosphere is over 96% carbon dioxide, with a pressure about 95 times Earth’s. The dense atmosphere and thick cloud layers trap incoming solar energy so efficiently that Venus has the highest surface temperature of any of the Sun’s planets, more than 860 °F (460 °C). Radar imaging indicates that the surface is dry and rocky, consisting mostly of gently rolling plains, broad depressions, and two large elevated regions analogous to continents on Earth; Venus also has impact craters, extensive lava fields, and massive shield volcanos. The interior is thought to be similar to that of Earth, with a metal core, a dense rocky mantle, and a less-dense rocky crust. Unlike Earth, Venus has no intrinsic magnetic field.
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