太陽系的九大行星之一。Venus（維納斯）得自羅馬神話中司愛情和美麗的女神。在夜晚天空中，除了月球，它是最明亮的天體。它離地球比其他大行星都近，在4,200萬公里以內。距離太陽1億750萬公里的平均距離處，沿近圓軌道繞日公轉。以225個地球日公轉一週，但經歷一個相位周則需時584日。從東到西逆向直轉，緩慢地每243日繞軸自轉一週。從大小和質量來看，金星和地球為一對孿生天體。金星完全被一層厚雲包圍，雲中主要含有濃硫酸微滴。金星大氣的成分，二氧化碳佔組成物質的96%以上，致使金星大氣具有極大的密度；金星的表面溫度高達460℃左右，為太陽系中所有行星上溫度最高的一個。與此高溫同時存在的是同樣高的表面壓力，約達90巴，為地球表面大氣壓力的90倍。用雷達繪製的金星地貌圖顯示出金星表面部分是綿延起伏的平原，另有幾處低窪地帶和兩處洲際規模的高原。
Venus
Second major planet from the sun. Named for the Roman goddess, Venus is, after the moon, the most brilliant natural object in the night sky. It comes closer to earth—about 26 million mi (42 million km)—than any other planet. Its orbit around the sun is nearly circular at a distance of 67 million mi (108 million km) and takes 225 days; its rotation, in retrograde motion, takes even longer (244 days). As viewed from earth, Venus undergoes phase changes similar to the moon's, going through one cycle of phases in 584 days and presenting nearly the same face to earth at each closest approach. It is seen only near sunrise or sunset and has long been known as both the morning and the evening star. Venus is a near twin of earth in size and mass but is completely enveloped by thick clouds of concentrated sulfuric-acid droplets. Its surface gravity is about 90% that of earth. Its atmosphere is over 96% carbon dioxide, with an atmospheric pressure about 90 times earth's. This and the thick cloud cover trap incoming solar energy so efficiently that Venus has the highest surface temperature of any of the sun's planets, about 860°F (460°C). Radar imaging indicates that most of Venus's surface consists of gently rolling plains and two large elevated regions analogous to continents on earth.
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