Venus

Venera 13 Lander Image of Venus Credit: NASA

Venus, the second closest planet to our sun, is named after the Roman goddess of love and beauty. The cloud-covered world is also one of the brightest natural objects in the night sky. In ancient times, Venus was often thought to be two different stars, the evening star and the morning star — that is, the ones that first appeared at sunset and sunrise. In Latin, they were respectively known as Vesper and Lucifer. In Christian times, Lucifer, or "light-bringer," became known as the name of Satan before his fall.

Diameter: 12,104 km
Mass: 4.87 x 10^24 kg (81.5% Earth)
Moons: None
Orbit Distance: 108,209,475 km (0.73 AU)
Orbit Period: 225 days
Surface Temperature: 462 °C
First Record: 17th century BC
Recorded By: Babylonian Astronomers

Venus is the hottest world in the solar system. Although Venus is not the planet closest to the sun, its dense atmosphere traps heat in a runaway version of the greenhouse effect that warms Earth. As a result, temperatures on Venus reach 870 degrees Fahrenheit (465 degrees Celsius), more than hot enough to melt lead. Probes that scientists have landed there have survived only a few hours before being destroyed.

Venus has a hellish atmosphere as well, consisting mainly of carbon dioxide with clouds of sulfuric acid, and scientists have only detected trace amounts of water in the atmosphere. The atmosphere is heavier than that of any other planet, leading to a surface pressure 90 times that of Earth.

The Venusian year — the time it takes to orbit the sun — is about 225 Earth days long. Normally, that would mean that days on Venus would be longer than years. However, because of Venus' curious retrograde rotation, the time from one sunrise to the next is only about 117 Earth days long.

Significant Dates:

• 650 BCE: Mayan astronomers make detailed observations of Venus, leading to a highly accurate calendar.
• 1610: Galileo Galilei documents the phases of Venus in The Starry Messenger.
• 1639: The first predicted transit of Venus is observed in England.
• 1761-1769: Two European expeditions to watch Venus cross in front of the sun lead to the first good estimate of the sun's distance from Earth.
• 1961: Radar returns from Venus are used to determine the most accurate value (at the time) for the sun's distance from Earth. (Published in 1962.)
• 1962: NASA's Mariner 2 reaches Venus and reveals the planet's extreme surface temperatures. It is the first spacecraft to send back information from another planet.
• 1970: The Soviet Union's Venera 7 sends back 23 minutes of data from the surface of Venus. It is the first spacecraft to successfully land on another planet.
• 1990-1994: NASA's Magellan spacecraft, in orbit around Venus, uses radar to map 98 percent of the planet's surface.
• 2005: The European Space Agency launches Venus Express to study the atmosphere and surface. The orbiter reached Venus in April 2006, and studied the planet through 2014.
• 2015: After launching in 2010, Japan's Akatsuki ("Dawn") orbiter achieves orbit around Venus.

Credit: Karl Tate/Space.com

Reference: Karl Tate/spacedotcom/Nasa Solar System