2024年12月22日:本星际云-（The Local Fluff） 2024年12月22日:本星际云-（The Local Fluff）--原图下载{mtitle title="本星际云"/}Illustration Credit: NASA, SVS,Adler, U. Chicago, Wesleyan说明: 恒星其实并不孤独。在我们的银河系的盘面上，大约有10%的可见物质是名为星际物质（ISM）的云气。然而，星际物质的分布并不均匀， 就连在太阳附近也是支离破碎的。因为星际物质非常稀薄，而且几乎不发光，所以侦测邻近星际物质的工作难度颇高。星际物质之主成分是氢气，因为它会吸收特定波长的光，所以可经由侦测最邻近恒星的星光得知它的存在。上面这幅呈现我们周围20光年内星际物质的暂订分布图，是根据地球轨道上的星际边界探测卫星 （IBEX），目前的观测及粒子侦测数据所建构出来的。这些观测显示，我们的太阳正在穿过 本星际云（Local Cloud），而这团云气则来自天蝎-半人马星协恒星形成区的外泛流。在接下来的一万年内，我们的太阳可能会穿出本星际云。我们对附近的星际物质所知不多，包括分布、起源、及它如何影响太阳和地球等细节都有待釐清。出乎预料的，最近的星际边界探测卫星量测指出，中性星际粒子流通过太阳系的方向正在改变之中。{lamp/}原文：{mtitle title="The Local Fluff"/}Illustration Credit: NASA, SVS,Adler, U. Chicago, WesleyanExplanation: The stars are not alone. In the disk of ourMilky Way Galaxy,about 10 percent of visible matter is in the form of gas called theinterstellar medium (ISM). The ISM isnot uniformand shows patchiness even near ourSun. It can be quite difficult to detect thelocal ISM because it is so tenuous and emits so little light. This mostly hydrogen gas, however, absorbs some veryspecific colors that can be detected in the light of thenearest stars. A working map of the localISM within 20 light-years,based on ongoing observations and particle detections from the Earth-orbiting Interstellar Boundary Exporer satellite (IBEX), is shown here. These observations indicate that ourSun is moving through aLocal Interstellar Cloud as this cloud flows outwards from theScorpius-Centaurus Association star forming region. Our Sun may exit the Local Cloud, also called the Local Fluff, during the next 10,000 years. Much remains unknown about the localISM, including details of its distribution,its origin, and how it affects theSun and the Earth.Unexpectedly, IBEXspacecraft measurements indicate that the direction from which neutral interstellar particles flow through our Solar System is changing.

2024年04月18日:正向星系NGC 1232-（Facing NGC 1232） 2024年04月18日:正向星系NGC 1232-（Facing NGC 1232）--原图下载{mtitle title="正向星系NGC 1232"/}Image Credit &Copyright:Neil Corke说明: 从我们在银河系的视角看出去，NGC 1232是个正向星系。这个庞大美丽、离我们约4千7百万光年远的螺旋星系，位于南天的波江座内，其跨幅将近有200,000光年。这幅由多色望远镜照片组合而成的NGC 1232清晰影像，呈现了这个遥远星系无比细緻的结构。从核心往外，星系的色泽从中心年老恒星的黄光，转变为宏伟螺旋臂上的泛蓝年轻星团和泛红的恒星形成区。NGC 1232在视觉上的小棒旋伴星系，其编录号NGC 1232A。然而它的估计距离远在3亿光年之外，因此不太可能和NGC 1232有互动。除此之外，醒目的带芒亮星近在我们银河系里，远比NGC 1232要近。{lamp/}原文：{mtitle title="Facing NGC 1232"/}Image Credit &Copyright:Neil CorkeExplanation: From our vantage point in theMilky Way Galaxy,we see NGC 1232 face-on.Nearly 200,000 light-years across, the big, beautifulspiral galaxyis located some 47 million light-years away in the flowing southernconstellation of Eridanus.This sharp, multi-color, telescopic imageof NGC 1232 includes remarkable details of the distant island universe.From the core outward, the galaxy'scolors change from the yellowishlight of old stars in the center to young blue starclusters and reddish star forming regions along the grand, sweepingspiral arms.NGC 1232's apparent, small, barred-spiral companion galaxyis cataloged as NGC 1232A.Distance estimates place it much farther though,around 300 million light-years away, and unlikely to beinteracting with NGC 1232. Of course, the prominent bright star with the spiky appearanceis much closer than NGC 1232 and lies well within our own Milky Way.

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11月22日:IC 342：尘豹座的隐藏星系-（IC 342: Hidden Galaxy in Camelopardalis） 2023年11月22日:IC 342：尘豹座的隐藏星系-（IC 342: Hidden Galaxy in Camelopardalis）--原图下载{mtitle title="IC 342：尘豹座的隐藏星系"/}Image Credit &Copyright: Steve Cannistra说明: 大小和我们附近明亮大螺旋星系相当的IC 342，位于北天具有长长脖子的鹿豹座之内，距离我们只有1千万光年远。IC 342是个庞大的宇宙岛，所以本来应是我们夜空中一个很吸睛的星系，不过受到银河系盘面的恒星、云气和尘埃之遮掩，只能隐约窥其身影。虽然IC 342发出的光因受到居间的宇宙云之消光而变暗，然而这幅清晰的望远镜影像，还是能呈现这个星系的尘埃云、年轻恒星团、以及从星系核伸出的长螺旋臂上之粉红恒星诞生区。IC 342最近可能刚发生过猛爆性的恒星诞生活动，此外它也够邻近，因此会透过重力影响本星系群和我们银河系的演化。{lamp/}原文：{mtitle title="IC 342: Hidden Galaxy in Camelopardalis"/}Image Credit &Copyright: Steve CannistraExplanation: Similarin size to large, bright spiral galaxies in our neighborhood,IC 342is a mere 10 million light-yearsdistantin the long-necked, northern constellationCamelopardalis.A sprawling island universe,IC 342 would otherwise be a prominent galaxy in our night sky,but it is hidden from clear view and onlyglimpsed through the veil of stars, gas and dust cloudsalong the plane of our own Milky Way galaxy.Even though IC 342's light is dimmed and reddened by interveningcosmic clouds,thissharp telescopic imagetraces the galaxy's own obscuring dust, young star clusters, andglowing star forming regions along spiral arms that wind far fromthe galaxy's core.IC 342 has undergone a recent burst ofstar formationactivity and is close enough to have gravitationally influencedthe evolution of thelocal groupof galaxies and the Milky Way.

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14日:NGC 7331及其后方的天体-（NGC 7331 and Beyond） 2023年09月14日:NGC 7331及其后方的天体-（NGC 7331 and Beyond）--原图下载{mtitle title="NGC 7331及其后方的天体"/}Image Credit &Copyright: Ian Gorenstein说明: 庞大美丽的螺旋星系NGC 7331，咸认是外观与我们银河系神似的星系。离我们约5千万光年远，位在北天飞马座方向的NGC 7331，很早就被归类为"螺旋星云"，然而，它也是18世纪着名的梅西叶星表未收录的较明亮星系之一。因为NGC 7331的盘面斜对着我们，望远镜的长曝光影像常带着很强的层次感。而在上面这幅清晰影像里，受到这个壮丽宇宙岛后方星系的衬托，这种层次感更加强烈。这些背景星系的视大小约莫是NGC 7331的10分之1，所以它们的距离也大约远上10倍。因此在影像里，它们看似和NGC 7331比邻纯是错觉。这个亦有鹿舔星系群之称的星系群，座落在银河盘面上方。(Deer Lick Group 鹿舔星系群）{lamp/}原文：{mtitle title="NGC 7331 and Beyond"/}Image Credit &Copyright: Ian GorensteinExplanation: Big, beautiful spiral galaxyNGC 7331is often touted as an analog to our ownMilky Way.About 50 million light-years distant in the northern constellationPegasus,NGC 7331 was recognized early on asa spiral nebula and is actually one of the brightergalaxiesnot included in Charles Messier'sfamous18th century catalog.Since the galaxy's diskis inclined to our line-of-sight, longtelescopic exposures often result in images that evokes a strongsense of depth.The effect is further enhancedin this sharp imageby galaxies that lie beyond the gorgeousisland universe.The most prominent background galaxies are about one tenth theapparent sizeof NGC 7331 and so lie roughly ten times farther away.Their close alignment on the sky with NGC 7331occurs just by chance.Lingering abovethe plane of the Milky Way, this striking visual grouping of galaxies isknown to some as theDeer Lick Group.