2025年11月16日
穿越土星环面
影像提供: NASA, ESA, JPL, ISS, Cassini Imaging Team; 影像处理: Fernando Garcia Navarro
说明: 这是土星吗？那它的环去哪里了？当伽利略在1612年仰望这颗行星时，他惊讶地发现，那对神秘的「凸起」会在某些时刻无声消失。那时的他并不明白，眼前的景象其实只是视角的错觉。直到数十年后，人们才揭开真相，那些凸起并非幻影，而是土星壮丽的光环。当地球恰巧与土星环平行时，薄如刀刃的环侧身面对我们，便隐没于宇宙的深色背景之中。土星环之薄远胜剃刀。卡西尼号探测器于2004至2017年间长驻土星，数度穿越这道环面。西班牙天文爱好者Fernando Garcia Navarro从庞大的卡西尼原始资料库中，细心找出2005年2月的一系列影像，经过重新拼接与著色，终于产生这张特色影像。画面中，蓝色的环平面如光之细线，静静划开土黄色的行星。土星的上层大气翻涌如绒雾，环的阴影在其间投下细致的暗纹。其卫星，土卫四（Dione）与土卫二（Enceladus），宛如悬于光环上的微星，于无声的虚空中浮现。
明日的图片: unusual comet tail
Crossing Saturn’s Ring Plane
Image Credit: NASA, ESA, JPL, ISS, Cassini Imaging Team; Processing: Fernando Garcia Navarro
Explanation: If this is Saturn, where are the rings? When Saturn’s “appendages” disappeared in 1612, Galileo did not understand why. Later that century, it became understood that Saturn‘s unusual protrusions were rings and that when the Earth crosses the ring plane, the edge-on rings will appear to disappear. This is because Saturn’s rings are confined to a plane many times thinner, in proportion, than a razor blade. In modern times, the robotic Cassini spacecraft that orbited Saturn frequently crossed Saturn’s ring plane during its mission to Saturn, from 2004 to 2017. A series of plane crossing images from 2005 February was dug out of the vast online Cassini raw image archive by interested Spanish amateur Fernando Garcia Navarro. Pictured here, digitally cropped and set in representative colors, is the striking result. Saturn’s thin ring plane appears in blue, bands and clouds in Saturn’s upper atmosphere appear in gold. Details of Saturn’s rings can be seen in high dark shadows. The moons Dione and Enceladus appear as bumps in the rings.
Tomorrow’s picture: unusual comet tail
