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Venus is the second-closest planet to the Sun, orbiting it every 224.7 Earth days. It is the brightest natural object in the night sky, except for the Moon, reaching an apparent magnitude of −4.6. Because Venus is an inferior planet, from Earth it never appears to venture far from the Sun: its elongation reaches a maximum of 47.8°. Venus reaches its maximum brightness shortly before sunrise or shortly after sunset, for which reason it is often called the Morning Star or the Evening Star.
Classified as a terrestrial planet, it is sometimes called Earth's "sister planet", for the two are similar in size, gravity, and bulk composition. Venus is covered with an opaque layer of highly reflective clouds of carbon dioxide, preventing its surface from being seen from space in visible light; this was a subject of great speculation until some of its secrets were revealed by planetary science in the twentieth century. Venus has the densest atmosphere of all the terrestrial planets, consisting mostly of carbon dioxide. The atmospheric pressure at the planet's surface is 90 times that of the Earth.
Venus' surface has been mapped in detail only in the last 20 years. It shows evidence of extensive volcanism, and some of its volcanoes may still be active today. Venus is thought to undergo periodic episodes of plate tectonics, in which the crust is subducted rapidly within a few million years, separated by stable periods of a few hundred million years.

Mean distance from the Sun: 0.7233 AU (108,200,000 km/67,230,000 mi)
Length of year: 225 days
Rotation period: 243 days (retrograde)
Mean orbital velocity: 35 km/sec (21.8 mi/sec)
Inclination of axis: 177.3°
Diameter: 12,102 km (7520 mi)
Number of observed satellites: 0
Comparisons with Earth:
Mean distance from Sun: 0.723 x Earth's
Diameter: 0.95 x Earth's
Mass: 0.81 x Earth's
Density: 0.9 x Earth's