土卫十五、土卫三十五与土卫十八
影像来源与版权:Cassini Imaging Team, SSI, JPL, ESA, NASA

说明:在这幅由卡西尼号太空船在2017年的告别轨道拍摄之集锦影像,等比例的呈现了土卫十五、土卫三十五与土卫十八,这3颗位在土星内围行星环里的小卫星。其中,土卫三十五是发现于卡西尼号在2005年所拍摄的影像。而土卫十五和土卫十八,则是首先发现于航行者一号与二号太空船的影像里。形似飞碟的土卫十五,轨道在土星明亮A环的外缘附近,土卫三十五位于A环狭窄的基勒环缝之内,而土卫十八则在A环较大的恩克环缝里。这些环系小卫星令人好奇的赤道突脊,可能是由长期累积的环系物质所构成。随着细小的土卫三十五在基勒环缝的边缘滑翔,它也在环系物质里激起了波浪。(Atlas 土卫十五;Daphnis 土卫三十五;Pan 土卫十八)
翻译:“每日一天文图”成大物理分站

Atlas, Daphnis, and Pan
Image Credit & Copyright: Cassini Imaging Team, SSI, JPL, ESA, NASA

Explanation: Atlas, Daphnis, and Pan are small, inner, ring moons of Saturn. They are shown at the same scale in this montage of images by the Cassini spacecraft that made its grand final orbit of the ringed planet in September 2017. In fact, Daphnis was discovered in Cassini images from 2005. Atlas and Pan were first sighted in images from the Voyager 1 and 2 spacecraft. Flying saucer-shaped Atlas orbits near the outer edge of Saturn’s bright A Ring while Daphnis orbits inside the A Ring’s narrow Keeler Gap and Pan within the A Ring’s larger Encke Gap. The curious equatorial ridges of the small ring moons could be built up by the accumulation of ring material over time. Even diminutive Daphnis makes waves in the ring material as it glides along the edge of the Keeler Gap.
Astronomy Picture of the Day 05/18/2019