Ganymede seen by Juno spacecraft

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图注： Ganymede is the largest and most massive natural moon of Jupiter, and at the same time, the largest moon in the solar system. It also stands out as it is the only moon in the solar system which has an internally generated magnetic field. This is likely created by a liquid iron or iron sulfide core. With a diameter of over 5,000 kilometers, it exceeds Mercury in size. Although it has more than twice the mass of Earth's Moon, it hosts weaker surface gravity than Mercury, Io, and the Moon due to its lower mean density. Ganymede's appearance is primarily composed of darker, heavily cratered regions, and brighter, less bombarded ones with deep grooves and ridges indicating geological activity. Whether this might be caused by tidal heating is still subject to further analysis. The brighter regions make up around two-thirds of Ganymede's surface. The remaining area consists of dark regions, saturated with impact craters, which have been dated back to four billion years. It is assumed that the moon hosts a large saltwater ocean under its icy surface with extreme depths of up to 800 kilometers. Ganymede likely has a very tenuous oxygen atmosphere, comparable to that found on the Jupiter moon Europa. It cannot be interpreted as a sign of life. Instead, it is thought that hydrogen and oxygen are split up by radiation on the moon's surface. The first space probe to visit Ganymede was Pioneer 10, performing a high-speed flyby manoeuvre through the Jupiter system. Since then, it has been investigated by several other probes such as Galileo, New Horizons, and Juno. The Jupiter Icy Moons Explorer (JUICE) will be the first to actually enter orbit around Ganymede itself (in around 2034) to further study the moon's magnetic and icy surface. JUICE will impact Ganymede as the last act of its mission.
来源： NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill
来源链接

词汇表: 伽利略卫星 , 卫星

授权许可： 知识共享许可协议 Attribution 2.0 Generic 知识共享许可协议 Attribution 2.0 Generic 图标

文件 ( 图像 1.85 MB)

Infrared Reentry Analysis: Shuttle Orbiter Columbia

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图注： A composite image of the Space Shuttle Columbia's reentry, captured by NASA's Kuiper Airborne Observatory. The right hand side of the image was taken in infrared light with the left hand side taken in visible light. The image reveals the intense heating patterns encountered during descent. The temperature scale for the infrared image goes from violet at the coolest end to red at the hottest. We can see here that the wing and tail of the space shuttle are glowing the brightest, indicating that they are the hottest.
来源： NASA with minor adjustments by wikicommons user Ke4roh
来源链接

词汇表: 红外线（IR）
分类： 观测天文学 , 太空探索

授权许可： 公共领域 公共领域 图标

文件 ( 图像 3.07 MB)

Hubble Image of Barred Spiral Galaxy UGC 6093

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图注： This image from the Hubble Space Telescope shows the barred spiral galaxy UGC 6093. This galaxy has two spiral arms in its outer regions but the inner edge of each arm joins with the outer edge of a straight bar feature that goes across the galaxy's center. This galaxy has been classified as an active galaxy due to the emissions of certain lines in its spectrum. This indicates that the supermassive black hole that lies in the center of the galaxy is accreting gas from its surroundings. Unlike some active galactic nuclei (AGN), the center of this galaxy does not shine especially brightly in the visible light so its status as an AGN is not immediately visible from this image.
来源： ESA/Hubble & NASA
来源链接

词汇表: 活动星系核 , 超大质量黑洞 , 星系棒 , 光谱线

授权许可： 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 图标

文件 ( 图像 987.80 kB)

创世之柱

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为 OAE 制作

图注： 2022 年国际天文学联合会 OAE 天体摄影比赛静态天体图案类获奖作品。 本影像摄于2021年10月意大利威尼托大区的多洛米蒂自然公园（Parco Naturale Dolomiti），展现拉瓦雷多三峰（Tre Cime di Lavaredo）上空的壮丽星野。 画面左侧明亮光点为木星，此时正位于摩羯座。木星右下方、摩羯座双角星之间可见土星。木星上方延伸至水瓶座（黄道最大星座之一）区域。银河左侧北天区多为暗星，唯左上角泛白的飞马座双星"危宿三"（Enif）较醒目。 银河如天界雾霭自岩峰升腾，其左右分别悬着牛郎星（Altair/河鼓二）与织女星（Vega/织女一）——这对被银河分隔的"星界眷侣"呼应着中国七夕传说。现代天文学将二者与画面顶缘的天津四（Deneb）共组"夏季大三角"，构成北半球经典星象。 牛郎星作为巴比伦鹰座（Aquila）主星，承载着《埃塔纳史诗》中神鹰背负君王凌空瞰地的古老传说。古罗马时期，托勒密将鹰座下方新增的"安提诺乌斯"子星座（Antinous）解读为溺亡尼罗河的哈德良皇帝宠臣之魂。 织女星（银河右侧亮白星体）隶属天琴座，该星座以拥有行星状星云"环状星云"（Ring Nebula）闻名，展现恒星临终时抛射气体形成的瑰丽景象。 画面右缘显著弯曲排列的三星为大熊座北斗杓柄，其指向地平线附近的牧夫座主星大角星（Arcturus）。牧夫座风筝状星群可能源自巴比伦神"恩利尔"（Enlil）的天界投影，后被罗马人重构为驾驭"七牛星"（即北斗七星）的耕夫形象。 织女星正右方可见武仙座广袤星域，其下方与牧夫座左侧交界的半圆星群，则是希腊神话中克里特公主阿里阿德涅的冠冕——北冕座（Corona Borealis）。 画面左下角云层反光为人造光源所致。
来源： Giorgia Hofer/IAU OAE

词汇表: 摩羯座 , 灰尘 , 木星 , 银河系 , 土星 , 尘埃云 , 星际消光
分类： 银河系与星际介质 , 肉眼天文学

授权许可： 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 知识共享许可协议 署名 4.0 国际 (CC BY 4.0) 图标

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Iron Meteorite

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图注： This iron meteorite was originally found in Harriman, Tennessee, USA and is now held in the collection of the Smithsonian Natural History Museum, Washington DC, USA. The total mass of the meteorite was about 30kg. Here we see the interior after the meteorite was cut into pieces. Iron meteorites are largely composed of an iron-nickel. They also often have a crystalline structure which manifests here as a series of crossing shiny straight lines known as a Widmanstätten pattern. This is thought to have formed as the meteoroid (the object that would eventually fall through the Earth's atmosphere as a meteor and land on the ground as a meteorite) cooled very slowly in the vacuum of space in the early solar system. This led to the growth of this crystalline structure.
来源： Chuck Sutherland
来源链接

词汇表: 铁陨石 , 陨石 , 流星
分类： 地球 , 太阳系

授权许可： 公共领域 公共领域 图标

文件 ( 图像 4.51 MB)