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Venus

Distance from sun 108.2 million km, 0.7233 a.u.
Diameter 12,102 km, 0.949 Earth diameters
Mass 0.8149 times Earth's mass
Density 5.25
Gravity 0.878 times Earth's gravity, escape velocity 10.4 km/s
Rotation 243.01 Earth days
Orbit Eccentricity 0.0068
Orbit Inclination 3.394 degrees
Axis Tilt 177.3 degrees
Sidereal Period 224.701 Earth days
Synodic Period 583.92 Earth days

History: Because Venus only appeared at sunrise and sunset, the ancients believed it to be two different planets, Phosphorous (light-bringer), and Hesperus. The Greeks associated the planet with Aphrodite, the goddess of love, and Venus is the roman name for the goddess. Venus in medeival alchemy was associated with the metal copper.

Description: Because the Venusian atmosphere is so much thicker than our own, the atmosperic pressure on the surface of Venus is about 90 times that of earth. The clouds hide Venus's surface, but they reflect sunlight well, contributing to the planet's brightness. The clouds also cause a greenhouse effect, causing temperatures on the surface of about 500 degrees celcius (900 degrees farenheight). The atmosphere is mostly carbon dioxide, with small amounts of nitrogen. The clouds consist of mostly hydrochloric and hydroflouric acid. Although Venus's surface is hidden from view, it has been mapped by several space probes using radar. These maps show that the planet is till geologically active, with active volcanoes and lava flows evident. Venus is one of only three planets that rotate backwards, from east to west. It is also the slowest rotating planet in the solar system, doing so only once about every revolution about the sun.

Observation: Venus is very conspicuous object when visible, since it is the third brightest object in the sky with a magnitude of -4. It's so bright that if you know where to look, you can spot it during the day. The greatest elongation of Venus is larger than Mercury, at 48 degrees, and is far enough away from the sun that it can sometimes be seen in full darkness. Venus's sydonic period is about 20 months; 10 weeks between inferior conjunctions and greatest elongations and then 31 weeks until superior conjunction. At rare times, we can see the Venus pass across the disk of the sun, called a transit. These transits of Venus occur twice every 121 years, the two occurences are only eight years apart. The next transits of Venus will occur on June 8, 2004, and on June 6, 2012.

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