土星衛星的寂靜之舞
The Moving Moons of Saturn<br />
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<img src="http://i10.tinypic.com/33412df.gif" border="0" onclick="zoom(this)" onload="attachimg(this, 'load')" alt="" /><br />
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影像提供: Cassini Imaging Team, SSI, JPL, ESA, NASA <br />
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<font color="navy">Explanation: </font><br />
<font color="dimgray">The moons of Saturn never stop. A space traveler orbiting the ringed giant planet would witness a continuing silent dance where Saturn's multiple moons pass near each other in numerous combinations. Like a miniature Solar System, the innermost moons orbit Saturn the fastest. The above movie was centered on Saturn's moon Rhea, so that the moons Mimas and Enceladus appear to glide by. At 1,500 kilometers across, Rhea is over three times larger than the comparably sized Mimas and Enceladus. The Sun illuminates the scene from the lower right, giving all of the moons the same crescent phase. The above time lapse movie was created by the Saturn-orbiting robotic Cassini spacecraft over a period of about 40 minutes.</font> <br />
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<font color="navy">說明:</font><br />
<font color="dimgray">土星的衛星永不停歇。繞行這顆擁有行星環的巨行星之太空旅者，會目睹土星眾多衛星以多種組合相互靠近的連續靜謐之舞。土星系統就像一個小型的太陽系，最內圍的衛星繞行土星的速度也最快。上面這幅電影是以土衛五 (Rhea)為中心，所以土衛一 (Mimas)和土衛二 (Enceladus)看起來會飛掠而過。直徑1,500公里的土衛五，大小大約是體形相近的土衛一和土衛二之三倍以上。太陽從影像右下方的位置照耀這些天體，所以它們都具有相同的娥眉狀位相。上面這幅時序電影是由正在繞行土星的卡西尼號太空船所拍攝的，影像實際全長大約有四十分鐘。</font><br />
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<font size="2">資料來源: Scientific American<br />
Department of Physics, NCKU</font><font color="white"><font size="1"><br />
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