2023年12月12日:挪威上空的极光与银河-（Aurora and Milky Way over Norway） [2023年12月12日:挪威上空的极光与银河-（Aurora and Milky Way over Norway）--原图下载](https://apod.nasa.gov/apod/image/2312/ArcticNight_Cobianchi_2048.jpg"onMouseOver="if (document.images)document.imagename1.src='image/2312/ArcticNight_Cobianchi_1080_annotated.jpg';"onMouseOut="if (document.images)document.imagename1.src='image/2312/ArcticNight_Cobianchi_1080.jpg';){mtitle title="挪威上空的极光与银河"/}Image Credit & Copyright: Giulio Cobianchi说明: 天空中这二道庞大的拱形光弧是什么？左侧是我们较熟悉的银河系中央盘面；它是由众多银盘恒星和星云汇集而成，在影像里看似几乎环绕整个南天的光带。银河拱的下方，则有鏽红色的火星和弥漫的仙女大星系。然而这个酷寒的极区夜晚另有其他精采之处。在短短的数分钟期间，由极光聚成、伸展在北天的複层拱形光弧，突然出现在影像右侧。很显然的，地球大气高层的极光，远比恒星要邻近。在泛绿的极光拱弧上方，则可见到构成北斗七星的一群恒星。这幅主题影像，组合自2022年11月中旬摄于挪威．罗弗敦群岛的20张照片。{lamp/}原文：{mtitle title="Aurora and Milky Way over Norway"/}Image Credit & Copyright: Giulio CobianchiExplanation: What are these two giant arches across the sky?Perhaps the more familiar one, on the left, is the central band of our Milky Way Galaxy.This grand disk of stars and nebulas here appears to encircle much of the southern sky.Visible below the stellar arch is the rusty-orange planet Mars and the extended Andromeda galaxy.But this night had more! For a few minutes during this coldarctic night, a second giant arch appeared encircling part of the northern sky: an aurora.Auroras are much closer than stars as they are composed of glowing air high in Earth's atmosphere. Visible outside the green auroral arch is the group of stars popularly known as the Big Dipper. The featured digital composite of 20 images was captured in mid-November 2022 over the Lofoten Islands in Norway.

2023年10月06日:哈伯发现宇宙-（Edwin Hubble Discovers the Universe） 2023年10月06日:哈伯发现宇宙-（Edwin Hubble Discovers the Universe）--原图下载{mtitle title="哈伯发现宇宙"/}Image Credit & Copyright: CourtesyCarnegie Institution for Science说明: 我们的宇宙有多大？在攸关宇宙的诸多问题之中，这个疑问是1920年代二位大天文学家争辩的焦点，而如今我们称此次论战为天文大辩论。当时的许多天文学家认为，我们的银河系就是整个宇宙。而其他人则相信，我们的银河系只是众多的星系之一。在那次的大辩论里，双方各自细数其观点，但终究未能获得共识。不过3年后，一颗在“仙女大星云”内侦测到的变星提供了答案，上图是记录这项数据的玻璃负片之数位複製。当时哈伯比较不同时间点拍摄的影像，发现这个亮点的亮度有变化，因此他于1923年10月6日在底板上注记了个变（VAR）字。哈伯当下就知道最合理的解释是：这个亮点是遥远变星的影像。也因此，“仙女大星云”其实是仙女大星系，一个位阶和我们银河系相当的天体。这张在100年前加了注记的主题影像，其实并不出采，不过上头记录的变星，为人类打开一扇窗，而我们从此知道，我们所见到的宇宙出乎预料的庞大。{lamp/}原文：{mtitle title="Edwin Hubble Discovers the Universe"/}Image Credit & Copyright: CourtesyCarnegie Institution for ScienceExplanation: How big is our universe?This question, among others, was debated by two leading astronomers in 1920 in what has sincebecome known as astronomy'sGreat Debate. Many astronomers then believed that our Milky Way Galaxy was the entire universe. Many others, though, believed that our galaxy was just one of many. In the Great Debate, each argument was detailed, but no consensus was reached. The answer came over three years later with the detected variation of single spot in the Andromeda Nebula, as shown on the original glass discovery plate digitally reproduced here.When EdwinHubble compared images, he noticed that thisspot varied, and on October 6, 1923wrote "VAR!" on the plate. The best explanation, Hubble knew, was that this spot was the image of a variable star that was very far away.So M31 was really the Andromeda Galaxy -- a galaxy possibly similar to our own. Annotated 100 years ago, the featured image may not be pretty, but the variable spot on it opened a windowthrough which humanity gazed knowingly, for the first time, into a surprisingly vast cosmos.

2023年09月06日:黑斯望远镜探索高能波段的天空-（HESS Telescopes Explore the High-Energy Sky） 2023年09月06日:黑斯望远镜探索高能波段的天空-（HESS Telescopes Explore the High-Energy Sky）--原图下载2023 September 6 {mtitle title="黑斯望远镜探索高能波段的天空"/}Video Credit & Copyright: Jeff Dai(TWAN), H.E.S.S. Collaboration; Music: Ibaotu catalog number 1044988 (Used with permission)说明: 这些或许看起来很像现代机械恐龙的装置，是监探天空的旋转巨眼。黑斯望远镜 (HESS；高能立体视野望远镜)，是由4座12米口径的反射式望远镜，与及它们中心环拱的一座较大口径28米望远镜所共同组成。它们是设计来侦测名为切伦科夫辐射的奇特蓝光亮闪，这种辐射是带电粒子，在空气中移动的速度略高于空气中的光速时所产生的。整体来说，当来自遥远辐射源的伽玛射线撞击地球大气的分子，造成带电粒子簇射就会产生切伦科夫辐射。黑斯望远镜能侦测来自宇宙深处，能量高达兆电子伏特（TeV）的高能光子。座落于纳米比亚、自2003年就开始运转的黑斯望远镜，任务标的是要搜寻暗物质，并且已找到超过50个会发出高能辐射的辐射源，其中包括超新星遗迹和内藏超大质量黑洞的星系核。在上面这部以银河系及大、小麦哲伦星系为背景所拍摄的缩时影片里，黑斯望远镜迴旋和凝视，而视野里也偶而会出现飞掠而过的地球人造卫星。{lamp/}原文：{mtitle title="HESS Telescopes Explore the High-Energy Sky"/}Video Credit & Copyright: Jeff Dai(TWAN), H.E.S.S. Collaboration; Music: Ibaotu catalog number 1044988 (Used with permission)Explanation: They may look like modern mechanical dinosaurs, but they are enormous swiveling eyes that watch the sky.The High Energy Stereoscopic System (H.E.S.S.) Observatory is composed of four 12-meter reflecting-mirror telescopes surrounding a larger telescope housing a 28-meter mirror.They are designed to detect strange flickers of blue light -- Cherenkov radiation --emitted when charged particles move slightly faster than the speed of light in air. This light is emitted when a gamma ray from a distant source strikes a molecule in Earth's atmosphere and starts a charged-particle shower. H.E.S.S. is sensitive to some of the highest energy photons (TeV) crossing the universe. Operating since 2003 in Namibia, H.E.S.S. has searched for dark matter and has discovered over 50 sources emitting high energy radiation including supernova remnants and the centers of galaxies that contain supermassive black holes. Pictured in June, H.E.S.S. telescopes swivel and stare in time-lapse sequences shot in front of our Milky Way Galaxy and the Magellanic Clouds -- as the occasional Earth-orbiting satellite zips by.

2023年07月02日:南极洲上空的银河和极光-（Milky Way and Aurora over Antarctica） 2023年07月02日:南极洲上空的银河和极光-（Milky Way and Aurora over Antarctica）--原图下载{mtitle title="南极洲上空的银河和极光"/}Image Credit & Copyright: LI Hang说明: 它是那个漫漫长夜较出采的天空景观之一。在该时的南极洲某些地区，不但时值寒冬，太阳更是连续数星期都未曾冒头。然而在中国的南极中山站，人们有时会顶着酷寒出门拍摄精采的夜空。这幅主题影像，即是在2015年7月中旬南极夜行将结束时，某次冒险出门之所得。当时上指的广角镜头，不但记录了下方的地面，更捕捉到影像顶端另一侧地面的景观。影像的前景有正在拍照的同事，远处有球形的卫星接收器和数座风车 。而夜空则散布着点点繁星，其中包括天狼星和老人星。在远方的背景里，从地平线伸展到另一侧地平线的，是我们银河系的中央盘面。而在头顶附近的更遥远后方，可见到以弥漫光斑之姿现身的大与小麦哲伦星系，这二个邻近我们庞大银河系的伴星系。{lamp/}原文：{mtitle title="Milky Way and Aurora over Antarctica"/}Image Credit & Copyright: LI HangExplanation: It was one of the better skies of this long night.In parts of Antarctica, not only is it winter, but the Sun can spend weeks below the horizon.At China's Zhongshan Station, people sometimes venture out into the cold to photograph a spectacular night sky.The featured image from one such outing was taken in mid-July of 2015, just before the end of this polar night.Pointing up, the wide angle lens captured not only the ground at the bottom, but at the top as well. In the foreground, a colleague is taking pictures.In the distance, a spherical satellite receiver and several windmills are visible.Numerous stars dot the night sky, including Sirius and Canopus.Far in the background, stretching overhead from horizon to horizon, is the central band of our Milky Way Galaxy.Even further in the distance, visible as extended smudges near the top, are the Large and Small Magellanic Clouds, satellite galaxies near our huge Milky Way Galaxy.

2023年05月29日:蓝绿色仙境上空的银河-（Milky Way over a Turquoise Wonderland） [2023年05月29日:蓝绿色仙境上空的银河-（Milky Way over a Turquoise Wonderland）--原图下载](https://apod.nasa.gov/apod/image/2305/SeaBlueSky_Horalek_960.jpg"onMouseOver="if (document.images)document.imagename1.src='image/2305/SeaBlueSky_Horalek_960_annotated.jpg';"onMouseOut="if (document.images)document.imagename1.src='image/2305/SeaBlueSky_Horalek_960.jpg';){mtitle title="蓝绿色仙境上空的银河"/}Image Credit & Copyright: Petr Horálek /Institute of Physics in Opava,Sovena Jani说明: 那里有什么在发光？答案取决于提问是指海还是天？在海中，不寻常的蓝色辉光是来自生物发光（译注：俗称蓝眼泪）。具体来说，微弱的光来自夜光虫，亦即受到激荡海浪激发的单细胞浮游生物。浮游生物则利用它们的辉光来惊吓和照亮捕食者。于今年的2月中旬，蓝眼泪在马尔地夫的一座小屿附近格外活跃，因此这位天文摄影者称之为蓝绿色的仙境。而作为对比，当时的天空更是充满很熟悉的恒星和星云之辉光。从人为照亮的绿色植物后方升起的泛白光带，是由数十亿颗恒星聚成的银河系中央盘面。此外，在天空中还可见到左侧的半人马座欧米茄星团，以及中间着名的南十字 星官。影像中的泛红星云，则有中右侧的明亮船底大星云及右上角的广袤甘姆星云。{lamp/}原文：{mtitle title="Milky Way over a Turquoise Wonderland"/}Image Credit & Copyright: Petr Horálek /Institute of Physics in Opava,Sovena JaniExplanation: What glows there? The answer depends: sea or sky?In the sea, the unusual blue glow is bioluminescence.Specifically, the glimmer arises from Noctiluca scintillans, single-celled plankton stimulated by the lapping waves.The plankton use their glow to startle and illuminate predators. This mid-February display on an island in the Maldives was so intense that the astrophotographer described it as a turquoise wonderland.In the sky, by contrast, are the more familiar glows of stars and nebulas.The white band rising from the artificially-illuminated green plants is created by billions of stars in the central disk of our Milky Way Galaxy. Also visible in the sky is the star cluster Omega Centauri, toward the left, and the famous Southern Cross asterism in the center.Red-glowing nebulas include the bright Carina Nebula, just right of center, and the expansive Gum Nebula on the upper right.

2023年03月22日:M31：仙女大星系-（M31: The Andromeda Galaxy） 2023年03月22日:M31：仙女大星系-（M31: The Andromeda Galaxy）--原图下载{mtitle title="M31：仙女大星系"/}Image Credit & Copyright: Abdullah Al-Harbi说明: 你能看多远？ 人类肉眼能轻易见到的最远天体是M31 (仙女大星系)，离我们有2百多万光年远。不过，如果没借助于望远镜，这个庞大的螺旋星系，看起来只是仙女座的一团不起眼的暗淡弥漫云气。在这幅以最邻近大星系为主题的15小时长曝光望远镜数位组合影像里，仙女大星系明亮的泛白核心、蜿蜒黝黑的尘埃带、明亮的泛蓝螺旋臂、与泛红的发射星云皆历历在目。不过，我们怎么知道这团”螺旋星云“真的有这么远？此提问是着名的1920年Shapley-Curtis大辩论之中心议题。后来在1920年代，经由观测能分辨、带有规律亮度变化的恒星，找出了它们的真实距离，从而测定了M31的距离。所得到的结果证实M31是个位阶与我们银河系相当的天体，而这个结论， 也让宇宙的规模远远超出先前所想的。{lamp/}原文：{mtitle title="M31: The Andromeda Galaxy"/}Image Credit & Copyright: Abdullah Al-HarbiExplanation: How far can you see?The most distant object easily visible to the unaided eye is M31, the great Andromeda Galaxy, over two million light-years away. Without a telescope, even this immense spiral galaxy appears as an unremarkable, faint, nebulous cloud in the constellation Andromeda. But a bright white nucleus, dark winding dust lanes, luminous blue spiral arms, and bright red emission nebulas are recorded in this stunning fifteen-hour telescopic digital mosaic of our closest major galactic neighbor. But how do we know this spiral nebula is really so far away?This question was central to the famous Shapley-Curtis debate of 1920. M31's great distance was determined in the 1920s by observations that resolved individual stars that changed their brightness in a way that gave up their true distance.The result proved that Andromeda is just like our Milky Way Galaxy -- a conclusion making the rest of the universe much more vast than had ever been previously imagined.