some discussion about venus planet.....

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Venus is named after the Roman goddess of love. The adjective Venusian is commonly used for Venus, but the Latin adjective is Venereal, which is avoided because of its modern association with sexually transmitted diseases. Some astronomers use Cytherean, which comes from Cytherea, another name for Aphrodite in ancient Greek Mythology. Other less common adjectives include Venerean, Venerian, and Veneran. The Chinese, Korean, Japanese and Vietnamese cultures refer to the planet as the metal star, based on the Five Elements. Orbital characteristics Orbit Although all planets' orbits are elliptical, Venus's orbit is the closest to circular, with an eccentricity of less than 1%. As Venus is closer to the Sun than the Earth is, it always appears in roughly the same direction from Earth as the Sun (the greatest elongation is 47.8°), so on Earth it can usually only be seen a few hours before sunrise or a few hours after sunset. However, when at its brightest, Venus may be seen during the daytime, making it the only heavenly body that can be seen both day and night besides the Moon (except for the occasional nova, such as the one that created the Crab Nebula). It is sometimes referred to as the "Morning Star" or the " Evening Star", and when it is visible in dark skies it is by far the brightest star-like object in the sky. The cycle between one maximum elongation and the next lasts 584 days. After these 584 days Venus is visible in a position 72 degrees away from the previous one. Since 5* 584= 2920, which is equivalent to 8* 365 Venus returns to the same point in the sky every 8 years (minus two leap days). This was known as the Sothis cycle in ancient Egypt, and was familiar to the Maya as well. Another association is with the Moon, because 2920 days equal almost exactly 99 lunations ( 29.5* 99= 2920.5). At inferior conjunction, Venus can get closer to earth than any other planet--little more than 100 times the Moon's average distance. On December 16th, 1850, Venus reached the lowest distance to earth since 1800, with a value of 0.26413854 AU= 39,514,827 kilometres. This will be the closest approach of Venus to Earth until December 16th, 2101 when Venus will reach a distance of 0.26431736 AU= 39,514,578 kilometres to earth. Rotation Venus has a slow retrograde rotation, meaning it rotates from east to west, instead of west to east as most of the other major planets do. ( Pluto and Uranus also have retrograde rotation, though Uranus's axis, tilted at 97.86 degrees, almost lies in its orbital plane.) A slow retrograde rotation is thought to have developed as a consequence of tidal forces, friction, and solar heating of Venus' thick atmosphere.[1] If the Sun could be seen from Venus' surface, it would appear to rise in the west and set in the east for a day-night cycle of 116.75 Earth days (Venus' mean solar day), and a Venusian year would thus last 1.92 Venusian "days". At the equator, Venus' surface rotates at a mere 6.5 km/h (4 mph). In addition to this unusual retrograde rotation, the periods of Venus' rotation and of its orbit are synchronized in such a way that it always presents the same face toward Earth when the two planets are at their closest approach ( 5.001 Venusian solar days between each inferior conjunction). This may simply be a coincidence, but there is some speculation that this may be the result of tidal locking, with tidal forces affecting Venus' rotation whenever the planets get close enough together —although the tides raised by Venus on Earth are vanishingly small. Ultraviolet image of Venus' clouds as seen by the Pioneer Venus Orbiter ( February 26, 1979). The immense C- or Y-shaped features which are visible only in these wavelengths are individually short lived, but reform often enough to be considered a permanent feature of Venus' clouds. Venus has an atmosphere consisting mainly of carbon dioxide and a small amount of nitrogen, with a pressure at the surface about 90 times that of Earth (a pressure equivalent to a depth of 1 kilometer under Earth's oceans); its atmosphere is also roughly 90 times more massive than ours. This enormously CO2-rich atmosphere results in a strong greenhouse effect that raises the surface temperature more than 400 °C (750 °F) with temperatures at the surface reaching extremes as great as 500 °C (930 °F) in low elevation regions near the planet's equator. This makes Venus's surface hotter than Mercury's, even though Venus is nearly twice as distant from the Sun and only receives 25% of the solar irradiance (2613.9 W/m² in the upper atmosphere, and just 1071.1 W/m² at the surface). Owing to the thermal inertia and convection of its dense atmosphere, the temperature does not vary significantly between the night and day sides of Venus, despite its extremely slow rotation. Upper atmosphere winds circling the planet approximately every 4 Earth-days help distribute the heat to other areas on the surface. The solar irradiance is so much lower at the surface of Venus because the planet's thick cloud cover reflects the majority of the sunlight back into space...... Ultraviolet image of Venus' clouds as seen by the Pioneer Venus Orbiter ( February 26, 1979). The immense C- or Y-shaped features which are visible only in these wavelengths are individually short lived, but reform often enough to be considered a permanent feature of Venus' clouds. Venus has an atmosphere consisting mainly of carbon dioxide and a small amount of nitrogen, with a pressure at the surface about 90 times that of Earth (a pressure equivalent to a depth of 1 kilometer under Earth's oceans); its atmosphere is also roughly 90 times more massive than ours. This enormously CO2-rich atmosphere results in a strong greenhouse effect that raises the surface temperature more than 400 °C (750 °F) with temperatures at the surface reaching extremes as great as 500 °C (930 °F) in low elevation regions near the planet's equator. This makes Venus's surface hotter than Mercury's, even though Venus is nearly twice as distant from the Sun and only receives 25% of the solar irradiance (2613.9 W/m² in the upper atmosphere, and just 1071.1 W/m² at the surface). Owing to the thermal inertia and convection of its dense atmosphere, the temperature does not vary significantly between the night and day sides of Venus, despite its extremely slow rotation. Upper atmosphere winds circling the planet approximately every 4 Earth-days help distribute the heat to other areas on the surface. The solar irradiance is so much lower at the surface of Venus because the planet's thick cloud cover reflects the majority of the sunlight back into space. This prevents most of the sunlight from ever heating the surface. Venus's bolometric albedo is approximately 60%, and its visual light albedo is even greater. Thus, despite being closer to the Sun than Earth, the surface of Venus is not as well heated and even less well lit by the Sun. In the absence of any greenhouse effect, the temperature at the surface of Venus would be quite similar to Earth. A common conceptual misunderstanding regarding Venus is the mistaken belief that its thick cloud cover traps heat, as the opposite is actually true. The cloud cover keeps the planet much cooler than it would be otherwise. The immense quantity of CO 2 in the atmosphere is what traps the heat by the greenhouse mechanism.