2019 October 7
Io Eclipse Shadow on Jupiter from Juno
Image Credit & License: NASA/JPL-Caltech/SwRI/MSSS; Processing: Kevin M. Gill
Explanation: What’s that dark spot on Jupiter? It’s the shadow of Jupiter’s most volcanic moon Io. Since Jupiter shines predominantly by reflected sunlight, anything that blocks that light leaves a shadow. If you could somehow be in that shadow, you would see a total eclipse of the Sun by Io. Io’s shadow is about 3600 kilometers across, roughly the same size as Io itself — and only slightly larger than Earth’s Moon. The featured image was taken last month by NASA’s robotic Juno spacecraft currently orbiting Jupiter. About every two months, Juno swoops close by Jupiter, takes a lot of data and snaps a series of images — some of which are made into a video. Among many other things, Juno has been measuring Jupiter’s gravitational field, finding surprising evidence that Jupiter may be mostly a liquid. Under unexpectedly thick clouds, the Jovian giant may house a massive liquid hydrogen region that extends all the way to the center.
影像提供与授权: NASA/JPL-Caltech/SwRI/MSSS; 影像处理: Kevin M. Gill
说明: 木星表面的暗斑是什么？它是木星火山活动最剧烈的木卫一之影子。因为木星的光主要来自反射阳光，所以任何挡住阳光的天体都会留下影子。假如你能站在这片影子里，你将会见到木卫一带来的日全食。木卫一影子的宽度约为3600公里，约莫和木卫一本身等宽，只比月亮要大上一丁点。这幅摄于上个月的主题 影像，拍摄者是美国航太总署目前正在绕行木星的的朱诺号太空船。朱诺号大约每二个月，近距离掠过木星一次，同时记录大量数据和拍摄一系列影像，其中部分用于组成这类影片。在诸多发现中，朱诺号量测了木星的重力场，并意外找到木星可能是颗液态行星的证据。在异常厚重的云层之下，木星可能有个一直延伸到中心的深厚液态氢层。