2021年01月14日
Aurora Slathers Up the Sky
Image Credit: Jack Fischer, Expedition 52, NASA
Explanation: Like salsa verde on your favorite burrito, a green aurora slathers up the sky in this 2017 June 25 snapshot from the International Space Station. About 400 kilometers (250 miles) above Earth, the orbiting station is itself within the upper realm of the auroral displays. Aurorae have the signature colors of excited molecules and atoms at the low densities found at extreme altitudes. Emission from atomic oxygen dominates this view. The tantalizing glow is green at lower altitudes, but rarer reddish bands extend above the space station’s horizon. The orbital scene was captured while passing over a point south and east of Australia, with stars above the horizon at the right belonging to the constellation Canis Major, Orion’s big dog. Sirius, alpha star of Canis Major, is the brightest star near the Earth’s limb.
Tomorrow’s picture: pixels in space
满天的极光
影像提供: Jack Fischer, Expedition 52, NASA
说明: 2017年6月25日摄于国际太空站的这幅影像里，泛绿极光如墨西哥卷饼上的萨尔萨辣酱般抹遍天空。位在400公里高空轨道上的太空站，本身位在极光国度的上缘。极光具有极高空、低密度环境中，激发态分子和原子所发出的特征色泽。在这片视野里，最醒目的是源自氧原子之极光。这些迷人的辉光，较低处的色泽泛绿，而在略高于太空站之上，则形成较罕见的泛红光带。这幅摄于太空站通过澳洲东南方上空某点的轨道景观，右侧地平面上方有猎人的大狗──大犬座内的恒星，而大犬座的α星（天狼星），则是地球临边附近那颗最亮的恒星。
明日的图片: pixels in space
