2025年02月03日:沃夫-瑞叶恆星124:恆星风机器-（Wolf-Rayet Star 124: Stellar Wind Machine） 2025年02月03日:沃夫-瑞叶恆星124:恆星风机器-（Wolf-Rayet Star 124: Stellar Wind Machine）--原图下载{mtitle title="沃夫-瑞叶恆星124:恆星风机器"/}Image Credit: Hubble Legacy Archive,NASA,ESA; Processing & License: Judy Schmidt说明: 有些恒星爆炸的过程极为缓慢。罕见、大质量的沃夫-瑞叶型恒星，极端高温而且极端活跃，它们几乎是在望远镜的注视下缓缓崩解。因为在猛烈恒星风的吹送下，恒星会喷出一团团通常超过30倍地球质量的光亮气体。例如于上面这张影像中心的沃夫-瑞叶型恒星124（WR 124），就以此在周围产生了宽约6光年的M1-67星云。在过去2万年之中，为何这颗恒星会缓缓自我分解，其细节仍是研究的题材。WR 124位在北天的天箭 座内，离我们约有15,000光年远。沃夫-瑞叶型恒星的宿命，可能会因它有多少质量而异，不过，许多可能会以壮观的超新星或伽玛射线爆发，来终结它们的生命。{lamp/}原文：{mtitle title="Wolf-Rayet Star 124: Stellar Wind Machine"/}Image Credit: Hubble Legacy Archive,NASA,ESA; Processing & License: Judy SchmidtExplanation: Some stars explode in slow motion. Rare, massive Wolf-Rayet stars are so tumultuous and hot that they are slowly disintegrating right before our telescopes. Glowing gas globs each typically over 30 times more massive than the Earth are being expelled by violent stellar winds. Wolf-Rayet star WR 124, visible near the featured image center,is thus creating the surrounding nebula known as M1-67, which spans sixlight years across.Details of why this star has been slowly blowing itself apart over the past 20,000 years remains a topic of research. WR 124 lies 15,000 light-years away towards the constellation of the Arrow (Sagitta). The fate of any given Wolf-Rayet star likely depends on how massive it is, but many are thought to end their lives with spectacular explosions such as supernovas or gamma-ray bursts.

2025年02月02日:阿特拉斯彗星发生崩解-（Comet G3 ATLAS Disintegrates） 2025年02月02日:阿特拉斯彗星发生崩解-（Comet G3 ATLAS Disintegrates）--原图下载{mtitle title="阿特拉斯彗星发生崩解"/}Image Credit: Lionel Majzik说明: 阿特拉斯彗星发生了什么事？ 自1月中旬掠过太阳附近后，这颗彗星的彗发就变得越来越昏暗。到了1月下旬，阿特拉斯彗星（C/2024 G3 ATLAS）几乎成为了一颗无头的彗星，儘管它在地球南半球的夜空中依然曳着壮观的彗尾。 上面这幅摄于智利 里奥乌塔多镇的组合影像，呈现了阿特拉斯彗星在1月连续数晚的照片。从中可清楚看出，彗星的彗发在早期照片里的亮度（左侧），比在后期（右侧）更明亮且更紧实。 发生这种改变的主要原因，很可能是彗星由冰与岩石组成的彗核已经崩解。阿特拉斯彗星在近日点时，曾深入水星轨道之内的太阳系内围，而该处的高温环境曾摧毁了许多的彗星。儘管如此，阿特拉斯彗星零落的残骸，仍会继续绕太阳运行。{lamp/}原文：{mtitle title="Comet G3 ATLAS Disintegrates"/}Image Credit: Lionel MajzikExplanation: What's happening to Comet G3 ATLAS?After passing near the Sun in mid-January, the head of the comet has become dimmer and dimmer.By late January, Comet C/2024 G3 (ATLAS) had become a headless wonder -- even though it continued to show impressive tails after sunset in the skies of Earth's Southern Hemisphere.Pictured are images of Comet G3 ATLAS on successive January nights taken from Río Hurtado, Chile.Clearly, the comet's head is brighter and more centrally condensed on the earlier days (left) than on later days (right). A key reason is likely that the comet's nucleus of ice and rock, at the head's center, has fragmented.Comet G3 ATLAS passed well inside the orbit of planet Mercury when at its solar closest, a distance that where heat destroys many comets. Some of comet G3 ATLAS' scattering remains will continue to orbit the Sun.

2025年01月28日:乌拉圭上空的阿特拉斯彗星-（Comet G3 ATLAS over Uruguay） 2025年01月28日:乌拉圭上空的阿特拉斯彗星-（Comet G3 ATLAS over Uruguay）--原图下载{mtitle title="乌拉圭上空的阿特拉斯彗星"/}Image Credit & Copyright: Mauricio Salazar说明: 彗星可以是庞然大物。在离太阳很远时，彗星的大小是指由冰和岩石构成的坚实彗核，其宽度通常仅有数公里，甚至比小卫星还要娇小。不过，当来到太阳附近时，彗核会释出尘埃和气体，形成细长的彗尾，而彗尾可能极长，其长度甚至可超过地球与太阳的间距。 如这幅影像所示，阿特拉斯彗星（C/2024 G3 ATLAS）曳着大把反射阳光的尘埃及发光气体长尾，而其跨幅为满月视大小的数倍之多。在长曝光的相机影像里，彗星的彗尾之规模远胜于肉眼所见。 这张大约一週前摄于乌拉圭 圣荷西市马霍马山脉的主题影像，呈现了阿特拉斯彗星悬在绿树和青草地上空的壮丽景象。在地球南半球的日落后天空中，阿特拉斯彗星曾经非常吸睛，但随着它逐渐远离太阳，其亮度也在减弱，让它壮观的彗尾愈来愈难以再现。{lamp/}原文：{mtitle title="Comet G3 ATLAS over Uruguay"/}Image Credit & Copyright: Mauricio SalazarExplanation: Comets can be huge.When far from the Sun, a comet's size usually refers to its hard nucleus of ice and rock, which typically spans a few kilometers -- smaller than even a small moon.When nearing the Sun, however, this nucleus can eject dust and gas and leave a thin tail that can spread to an enormous length -- even greater than the distance between the Earth and the Sun.Pictured, C/2024 G3 (ATLAS) sports a tail of sunlight-reflecting dust and glowing gas that spans several times the apparent size of a full moon, appearing even larger on long duration camera images than to the unaided eye.The featured image shows impressive Comet ATLAS over trees and a grass field in Sierras de Mahoma, San Jose, Uruguay about a week ago. After being prominent<?a> in the sunset skies of Earth's southern hemisphere, Comet G3 ATLAS is now fading as it moves away from the Sun, making its impressive tails increasingly hard to see.

2025年01月07日:新年元旦的极光与稳定极光红弧-（A New Year's Aurora and SAR Arc） 2025年01月07日:新年元旦的极光与稳定极光红弧-（A New Year's Aurora and SAR Arc）--原图下载{mtitle title="新年元旦的极光与稳定极光红弧"/}Image Credit & Copyright: Alessandra Masi说明: 元旦那天，天空出现二种红色辉光。元旦意味着地球周而复始，在1月1日那天回到其公转轨道的起点，而这天也离地球最接近太阳的近日点仅有数天之遥。 二种辉光之中，左侧的红色辉光是带着垂直线形结构的泛红极光，其起源是被太阳爆发推入地球大气的带电粒子。右侧的第二种名为稳定极光红弧的红色辉光，则是因为带电粒子流穿过地球大气所致。 儘管两道辉光都是红色的，但它们的微小色差，可能是因为极光的辐射源是氧及氮，而较高的稳定极光红弧只有氧辐射。这幅主题影像，是在今年的1月1日摄于义大利的皮耶韦迪卡多雷镇附近。{lamp/}原文：{mtitle title="A New Year's Aurora and SAR Arc"/}Image Credit & Copyright: Alessandra MasiExplanation: It was a new year, and the sky was doubly red. The new year meant that the Earth had returned to its usual place in its orbit on January 1, a place a few days before its closest approach to the Sun. The first of the two red skyglows, on the left, was a red aurora, complete with vertical rays, caused by a blast from the Sun pushing charged particles into Earth's atmosphere. The second red glow, most prominent on the far right, was possibly a SAR arc caused by a river of charged particles flowing across Earth's atmosphere. Although both appear red, the slight color difference is likely due to the aurora being emitted by both oxygen and nitrogen, whereas the higher SAR arc was possibly emitted more purely by atmospheric oxygen.The featured image was taken on January 1 from near Pieve di Cadore in Italy.

2024年12月29日:贝加尔湖冻结的甲烷气泡-（Methane Bubbles Frozen in Lake Baikal） 2024年12月29日:贝加尔湖冻结的甲烷气泡-（Methane Bubbles Frozen in Lake Baikal）--原图下载{mtitle title="贝加尔湖冻结的甲烷气泡"/}Image Credit & Copyright: Kristina Makeeva说明: 冻结在贝加尔湖气泡里的是什么？甲烷。 位于俄罗斯的贝加尔湖，是联合国教科文组织 的世界遗址之一，也是世界上体积最大、最古老及最深的湖泊，拥有世界百分之二十以上的淡水储量。这座湖泊也是庞大的甲烷（一种温室气体）储存库，一旦释放出来，可能会造成地球大气对红外光吸收的增加，导至地球平均温度的上升。很幸运的，目前释出的甲烷量，尚未对气候造成重大影响。然而，如果此区的温度大幅上升，或者贝加尔湖的水深显着下降，后果会如何目前仍然不明。影像中的这些气泡，是冬天来临在上浮时，被冻结在这座湖泊无比澄澈的湖冰里。{lamp/}原文：{mtitle title="Methane Bubbles Frozen in Lake Baikal"/}Image Credit & Copyright: Kristina MakeevaExplanation: What are these bubbles frozen into Lake Baikal?Methane. Lake Baikal, a UNESCO World Heritage Site in Russia, is the world's largest (by volume), oldest, and deepest lake, containing over 20% of the world's fresh water.The lake is also a vast storehouse of methane, a greenhouse gas that, if released, could potentially increase the amount of infrared light absorbed by Earth's atmosphere, and so increase the average temperature of the entire planet.Fortunately, the amount of methane currently bubbling out is not climatologically important.It is not clear what would happen, though, were temperatures to significantly increase in the region, or if the water level in Lake Baikal were to drop. Pictured, bubbles of rising methane froze during winter into the exceptionally clear ice covering the lake.

2024年12月27日:暮光时分的地球-（Planet Earth at Twilight） 2024年12月27日:暮光时分的地球-（Planet Earth at Twilight）--原图下载{mtitle title="暮光时分的地球"/}Image Credit: ISS Expedition 2 Crew,Gateway to Astronaut Photography of Earth,NASA说明: 在这张呈现地球海洋和云彩的壮丽影像里，当白画变成黑夜时，并没有明显的边界分隔日夜。分隔画夜的明暗界线其实是一个弥漫的区域，于此暮曙光区里，白画与黑夜缓缓过渡。在这幅影像里，阳光从右方入射，当它们穿过烟尘弥漫、滋养地球万物的对流层时，会受到过滤逐渐变红，然后再从云层反射造成影像里的淡红色泽。于影像右上角的白画地球边缘，可以清楚看见平流层顶，以及受到散射的蓝光逐渐隐没在黝黑的太空中。这幅影像，则是摄于轨道高390公里（211海浬）的国际大空站上。然而，如今端坐在家中的你，可上网观看地球的现况。{lamp/}原文：{mtitle title="Planet Earth at Twilight"/}Image Credit: ISS Expedition 2 Crew,Gateway to Astronaut Photography of Earth,NASAExplanation: No sudden, sharp boundary marks the passage of day into night inthis gorgeous viewof ocean and clouds overour fair planet Earth.Instead, the shadow line or terminator is diffuse and showsthe gradual transition to darkness we experience as twilight.With the Sun illuminating the scene from the right,the cloud tops reflect gently reddenedsunlight filteredthrough the dusty troposphere,the lowest layer of the planet's nurturing atmosphere.A clear high altitude layer,visible along the dayside's upper edge,scatters bluesunlight and fades into the blackness of space.This picture was taken from theInternational Space Stationorbiting at an altitude of 211nauticalmiles.Of course from home,you can check out the Earth Now.