什么是金星
太阳系的九大行星之一。Venus(维纳斯)得自罗马神话中司爱情和美丽的女神。在夜晚天空中,除了月球,它是最明亮的天体。它离地球比其他大行星都近,在4,200万公里以内。距离太阳1亿750万公里的平均距离处,沿近圆轨道绕日公转。以225个地球日公转一周,但经历一个相位周则需时584日。从东到西逆向直转,缓慢地每243日绕轴自转一周。从大小和质量来看,金星和地球为一对孪生天体。金星完全被一层厚云包围,云中主要含有浓硫酸微滴。金星大气的成分,二氧化碳占组成物质的96%以上,致使金星大气具有极大的密度;金星的表面温度高达460℃左右,为太阳系中所有行星上温度最高的一个。与此高温同时存在的是同样高的表面压力,约达90巴,为地球表面大气压力的90倍。用雷达绘制的金星地貌图显示出金星表面部分是绵延起伏的平原,另有几处低洼地带和两处洲际规模的高原。
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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