土卫十二的立体影像
影像来源与版权:Cassini Imaging Team, ISS, JPL, ESA, NASA; Stereo Image by Roberto Beltramini

说明:取出你的红/蓝眼镜,一起飘浮在土卫十二(Helene),这颗土星冰质小卫星之旁。姓名很适切的土卫十二(海伦),是四颗现知位在拉格朗日点上的特洛伊卫星之一。拉格朗日点是两颗大质量物体间的重力稳定位置,在此例中为土星和它较大的卫星土卫四。形状不规则的土卫十二(约36*32*30公里),位在导先土卫四的拉格朗日点上,另一颗冰质姐妹卫星土卫三十四,则位在落后的拉格朗日点上。这张清晰的立体影像,建构自卡西尼号2011年某次近距离飞越时所拍的二张照片。影像显示土卫十二面向土星的半球,部分表面上满布著撞击坑和沟状结构。
翻译:“每日一天文图”成大物理分站

Stereo Helene
Image Credit & Copyright: Cassini Imaging Team, ISS, JPL, ESA, NASA; Stereo Image by Roberto Beltramini

Explanation: Get out your red/blue glasses and float next to Helene, small, icy moon of Saturn. Appropriately named, Helene is one of four known Trojan moons, so called because it orbits at a Lagrange point. A Lagrange point is a gravitationally stable position near two massive bodies, in this case Saturn and larger moon Dione. In fact, irregularly shaped ( about 36 by 32 by 30 kilometers) Helene orbits at Dione’s leading Lagrange point while brotherly ice moon Polydeuces follows at Dione’s trailing Lagrange point. The sharp stereo anaglyph was constructed from two Cassini images captured during a close flyby in 2011. It shows part of the Saturn-facing hemisphere of Helene mottled with craters and gully-like features.
Astronomy Picture of the Day 06/15/2019