土星、土卫三、行星环及暗影

2022年1月23日

Saturn, Tethys, Rings, and Shadows
Image Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA

Explanation: Seen from ice moon Tethys, rings and shadows would display fantastic views of the Saturnian system. Haven’t dropped in on Tethys lately? Then this gorgeous ringscape from the Cassini spacecraft will have to do for now. Caught in sunlight just below and left of picture center in 2005, Tethys itself is about 1,000 kilometers in diameter and orbits not quite five saturn-radii from the center of the gas giant planet. At that distance (around 300,000 kilometers) it is well outside Saturn’s main bright rings, but Tethys is still one of five major moons that find themselves within the boundaries of the faint and tenuous outer E ring. Discovered in the 1980s, two very small moons Telesto and Calypso are locked in stable along Tethys’ orbit. Telesto precedes and Calypso follows Tethys as the trio circles Saturn.

Tomorrow’s picture: witch star?

土星、土卫三、行星环及暗影
影像提供: Cassini Imaging Team, SSI, JPL, ESA, NASA

说明: 从冰卫星土卫三看出去，土星环及其暗影交织出如梦似幻的土星系统景观。你最近没去土卫三吗？那么这幅由卡西尼号太空船所拍摄的壮丽环系影像，可拿来暂解渴望。在这幅摄于2005的影像里，中下方沐浴在阳光里、直径约1,000公里的土卫三，与土星这颗气态巨行星的中心相隔不到5个土星半径。依此间距（约300,000公里）来说，它位在土星主要亮环的外头，但仍是在暗淡稀薄E环内运行的5颗大卫星之一。在1980年代找到的二颗小卫星：土卫十三和土卫十四，则被锁在土卫三轨道的特定稳定位置上；土卫十三运行在土卫三前头，而土卫十四则堕后尾随，三者共轨绕行土星。 (Tethys 土卫三; Telesto 土卫十三; Calypso 土卫十四)

明日的图片: witch star?