Fantastic Venus

Unseen behind a shroud of thick clouds, man has fantasised about beautiful Venus for centuries. Then the space age changed everything - probes pierced her veil and revealed that Venus was like hell ... but that was only the beginning of the shattered dreams. After years in orbit, the latest probe has now burned up. Far from solving the mysteries, its data has deepened them, and may force geologists to overthrow 100 years of scientific dogma. Venus is the second-closest planet to the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love. 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.
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Venus is the second planet in distance from the Sun, but the hottest planet in the solar system (hotter than Mercury). Its hellish surface has broiling temperatures that make rocks glow red under a crushing atmosphere that shrouds the planet in thick layers of clouds. Venus is nearly the same size as Earth, but takes 243 days to rotate on its axis in the opposite direction. It also lacks a magnetic field and a moon. Why conditions on Venus and Earth are so different remains a major puzzle for planetary scientists. Venus circles the Sun at a distance of 108 million km (67 million mi) in a little over seven months (about 225 days). The planet was named for Venus, the Roman goddess of beauty.

Except for the Sun and the Moon, Venus is the brightest object in the sky. It is often called the morning star when it appears in the east at sunrise, and the evening star when it is in the west at sunset. In ancient times the evening star was called Hesperus and the morning star Phosphorus, Eosphoros, or Lucifer. Venus orbits the Sun at an average distance of about 108 million km (67 million mi), or 0.7233 astronomical units (AU). An AU is equal to the average distance between Earth and the Sun, or about 150 million km (93 million mi). Venus is the nearest planet to Earth in distance at about 41 million km (25.4 million mi) away at its closest approach. Venus circles the Sun once every 224.7 days in a counterclockwise direction, the same direction as the other planets in the solar system. Its axis is nearly vertical and its orbit is nearly circular so Venus does not experience seasons the way Earth and Mars do because of their more tilted axes and more elliptical orbits. Venus rotates very slowly, once every 243 Earth days. Venus’s rotation is retrograde, which means that the planet turns clockwise (from east to west) as seen looking down on its north pole. Earth and most other planets turn counterclockwise (from west to east).




Venus’s counterclockwise orbit and slow, clockwise rotation combine to make the periods of day and night on the planet very different from its 243-day period of rotation (called a sidereal day). A full solar day on Venus—the time when the Sun next passes the noon point in the sky—is 116.8 days long. Viewed from a spot on the equator of Venus, the Sun rises in the west and takes 58.4 days to cross the sky until it sets in the east. Night also lasts 58.4 days. Venus’s sidereal day (one complete rotation on its axis) is longer than its year (224.7 days), but the planet experiences almost two complete solar days per orbit around the Sun. On Earth, the solar day (24 hr) is four minutes longer than the sidereal day (23 hr 56 min) to add our planet’s extra counterclockwise orbital motion around the Sun to its counterclockwise rotation. As a result Earth counts 365 solar days and 366.2 sidereal days in a year.


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written by stranger on December 10, 2009

thanks for helping me!
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