Venus, in astronomy, the second planet from the sun. Except for the sun and the moon, Venus is generally the brightest astronomical object in the sky, displaying a brilliant white starlike appearance. It can be seen even during the day when it is at its brightest. At specific times during a year, Venus is either the first object seen in the western sky in the evening (when it moves toward Earth), or the last seen in the eastern sky in the morning (when it moves away from Earth). Ancient astronomers named the object they saw in the morning Phosphorus, and the one in the evening Hesperus. Later, when they realized it was the same object they were seeing twice, they called it Venus in honor of the Roman goddess of love and beauty.

Venus at a glance
Distance from the sun: Shortest--66,780,000 mi (107,480,000 km); Greatest--67,690,000 mi (108,940,000 km); Average--67,240,000 mi (108,210,000 km).
Distance from Earth: Shortest--23,700,000 mi (38,200,000 km); Greatest--162,200,000 mi (261,000,000 km).
Diameter: 7,521 mi (12,104 km).
Length of year: 225 Earth days.
Rotation period: 243 Earth days.
Temperature: 870 °F (465 °C).
Atmosphere: Carbon dioxide, nitrogen, water vapor, argon, carbon monoxide, neon, sulfur dioxide.
Number of satellites: None.