土星和六颗卫星
(原标题: Saturn and Six Moons)
2021-07-06
浏览次数: 39
土星有多少颗卫星？到目前为止，已经确认了82颗，最小的直径只有不到一公里。在这张合成照片中，我们可以看到它的六颗最大的卫星，其中13张是对这颗明亮的行星进行短曝光的，13张是对它最亮的暗淡卫星进行长曝光的，这张照片是在上个月的两周内拍摄的。土星最大的卫星土卫六比地球的月球大，甚至比水星略大，直径为5150公里，被拍到几乎绕着它的环状母行星运行了一个完整的轨道。土卫六是土星第一颗已知的天然卫星，由荷兰天文学家克里斯蒂安·惠更斯于1655年发现，与2019年宣布的几颗新发现的卫星形成对比。最右边的轨迹属于土卫八，土星的第三大卫星。土卫八的轨道半径非常大，只有一部分被捕捉到。这个月，土星带领木星穿越夜空，在日落后不久向东南方向升起，直到黎明之前都能看到。
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How many moons does Saturn have? So far 82 have been confirmed, the smallest being only a fraction of a kilometer across. Six of its largest satellites can be seen here in a composite image with 13 short exposure of the bright planet, and 13 long exposures of the brightest of its faint moons, taken over two weeks last month. Larger than Earth's Moon and even slightly larger than Mercury,Saturn's largest moon Titan has a diameter of 5,150 kilometers and was captured making nearly a complete orbit around its ringed parent planet. Saturn's first known natural satellite, Titan was discovered in 1655 by Dutch astronomer Christiaan Huygens, in contrast with several newly discovered moons announced in 2019. The trail on the far right belongs to Iapetus, Saturn's third largest moon. The radius of painted Iapetus' orbit is so large that only a portion of it was captured here. Saturn leads Jupiter across the night sky this month, rising soon after sunset toward the southeast, and remaining visible until dawn.
© Mohammad Ranjbaran; MR Thanks: Amir Ehteshami