2024年01月21日:1938年上密西根半岛的暴风雪-（The Upper Michigan Blizzard of 1938） 2024年01月21日:1938年上密西根半岛的暴风雪-（The Upper Michigan Blizzard of 1938）--原图下载{mtitle title="1938年上密西根半岛的暴风雪"/}Image Credit: Bill Brinkman; Courtesy: Paula Rocco说明: 你见过的暴风雪威力有这么大吗？在1938年，上密西根半岛世纪暴风雪期间，有些积雪的高度几乎和电线桿等高。86年前的这场风暴，很意外的在头两天就降下将近1公尺深的新雪。当大雪纷飞时，强阵风接着把雪堆叠到难以想像的高度，不但造成许多道路难以通行，就连除雪也成了不可能的任务。于是，除了居民寸步难行之外，轿车、校车和火车都深陷白雪里。更惨的是，当时还发生了一场大火；万幸这场雪灾和火灾只造成2人丧生，不过，有些学生困在学校里达数天之久。上面这张主题影像，是当地的一位居民摄于暴风雪刚过之后。这些大雪最后都消融了，然而，在地球雪区这种规模的连续暴雪，则有助于形成永久的冰川。{lamp/}原文：{mtitle title="The Upper Michigan Blizzard of 1938"/}Image Credit: Bill Brinkman; Courtesy: Paula RoccoExplanation: Yes, but can your blizzard do this?In the Upper Peninsula of Michigan's Storm of the Century in 1938, some snow drifts reached the level of utility poles.Nearly a meter of new and unexpected snow fell over two days in a storm that started 86 years ago this week. As snow fell and gale-force winds piled snow to surreal heights, many roads became not only impassable but unplowable; people became stranded, cars, school buses and a train became mired, and even a dangerous fire raged.Two people were killed and some students were forced to spend several consecutive days at school. The featured image was taken by a local resident soon after the storm.Although all of this snow eventually melted, repeated snow storms like this help build lasting glaciers in snowy regions of our planet Earth.

2024年01月03日:纽西兰上空的稳定极光红弧-（A SAR Arc from New Zealand） 2024年01月03日:纽西兰上空的稳定极光红弧-（A SAR Arc from New Zealand）--原图下载{mtitle title="纽西兰上空的稳定极光红弧"/}Image Credit & Copyright: Tristian McDonald;Text: Tiffany Lewis (Michigan Tech U.)说明: 这片极光周围的不寻常红晕是什么？它是稳定极光红弧（SAR）。稳定极光红弧是种罕见的现象，于1954年以后其存在方获得证实并加以研究。这幅本月稍早摄于纽西兰 Poolburn聚落，时值一场格外强烈的地球磁暴肆虐期间的广角主题影像，记录了几乎完整环抱较常见的绿与红极光之稳定极光红弧。稳定极光红弧的成因，至今仍是研究的课题，但很可能和在地球内部深处流动的熔铁所产生的地球防护磁场有关。这个磁场通常会把从太阳风带来的的带电粒子，导引到地球的极区。不过，它也会在近赤道的地方拘束了一圈离子，而且在太阳活动频繁时，这些离子可以从磁层中获得能量。这个离子环里的高能电子，会撞击地球电离层里一般极光发光高度上方的氧，激发它们发出红光。目前在进行的研究，发现有迹证显示稳定极光红弧甚至会变身为紫和绿色的STEVE。（ STEVE, Strong Thermal Emission Velocity Enhancement 增速导致的突发性热辐射）{lamp/}原文：{mtitle title="A SAR Arc from New Zealand"/}Image Credit & Copyright: Tristian McDonald;Text: Tiffany Lewis (Michigan Tech U.)Explanation: What is that unusual red halo surrounding this aurora? It is a Stable Auroral Red (SAR) arc.SAR arcs are rare and have only been acknowledged and studied since 1954. The featured wide-angle photograph, capturing nearly an entire SAR arc surrounding more common green and red aurora, was taken earlier this month from Poolburn, New Zealand, during an especially energetic geomagnetic storm.Why SAR arcs form remains a topic of research, but is likely related to Earth's protective magnetic field, a field created by molten iron flowing deep inside the Earth. This magnetic field usually redirects incoming charged particles from the Sun's wind toward the Earth's poles.However, it also traps a ring of ions closer to the equator, where they can gain energy from the magnetosphere during high solar activity.The energetic electrons in this ion ring can collide with and excite oxygen higher in Earth's ionosphere than typical auroras, causing the oxygen to glow red.Ongoing research has uncovered evidence that a red SAR arc can even transform into a purple and green STEVE.

2023年12月26日:IC 443：水母星云-（IC 443: The Jellyfish Nebula） 2023年12月26日:IC 443：水母星云-（IC 443: The Jellyfish Nebula）--原图下载{mtitle title="IC 443：水母星云"/}Image Credit & Copyright: David Payne说明: 为何会有水母悠游在恒星海里？影像中漂浮在亮星銊（右侧）附近的水母星云，其触手往中左方的弧形亮脊方向伸展。水母星云其实是气泡状超新星遗迹IC 443的一部份，是一颗大质量恒星爆炸后所留下的扩张碎片云。来自这个超新星爆炸的亮闪，大约在30,000年前首次传到地球。就像它在天文海洋里的同类--超新星遗迹蟹状星云一样，IC 443之内也藏着一颗星核崩塌后形成的中子星。水母星云离我们约5,000光年远。以此距离来换算，这张主题影像的跨幅约为140光年。（Jellyfish Nebula 水母星云; Eta Gem 銊）{lamp/}原文：{mtitle title="IC 443: The Jellyfish Nebula"/}Image Credit & Copyright: David PayneExplanation: Why is this jellyfish swimming in a sea of stars?Drifting near bright star Eta Geminorum, seen at the right, the Jellyfish Nebula extends its tentacles from the bright arcing ridge of emission left of center. In fact, the cosmic jellyfish is part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from a massive star that exploded. Light from the explosion first reached planet Earth over 30,000 years ago. Like its cousin in astronomical waters, the Crab Nebula supernova remnant IC 443 is known to harbor a neutron star -- the remnant of the collapsed stellar core. The Jellyfish Nebula is about 5,000 light-years away. At that distance, the featured image would span about 140 light-years across.

2023年12月23日:十二月的仲夏夜-（A December Summer Night） 2023年12月23日:十二月的仲夏夜-（A December Summer Night）--原图下载{mtitle title="十二月的仲夏夜"/}Image Credit &Copyright:Ian Griffin(Otago Museum)说明: 这幅在今年冬至附近，摄于地球南半球的纽西兰之8分钟长曝光影像，记录了静谧夜空的缤纷色彩。在这片南眺的视野里，恒星旋绕着顶缘外头的南天极，曳出短短的同心圆弧状星轨。在影像的中左方，有南十字群星的星轨及煤袋星云所造成的黝黑斑块。其中，南门二及马腹一的明亮泛黄与泛蓝星轨，更倒映在南岛奥塔哥半岛太平洋沿岸胡珀斯湾的海面上。此外，在12月的这个仲夏夜里，南极光也为山丘上方的天空抺上明亮的绿与红晕。左上角斜贯的淡绿光带，则是大气受到阳光激发的一连串化学反应所发出的气辉，这种高层大气的辉光，显然有别于因高能粒子撞击而触发的极光。{lamp/}原文：{mtitle title="A December Summer Night"/}Image Credit &Copyright:Ian Griffin(Otago Museum)Explanation: Colours of a serene evening sky are captured in this8 minute exposure, made nearthis December's solsticefrom New Zealand, southern hemisphere,planet Earth.Looking south, star trails form the short concentric arcs aroundthe rotating planet's south celestial polepositioned just off the top of the frame.At top and left of center are trails of the Southern Cross starsand a dark smudge from theMilky Way's Coalsack Nebula.Alpha and BetaCentauri make the brighter yellow and blue tinted trails,reflected below in the waters of Hoopers Inlet in the Pacific coast of the South Island'sOtago Peninsula.On that short December summer night,aurora australis alsogave luminous, green and reddish hues to the sky above the hills.Aurora shine as atoms and molecules in the upper atmosphereare excited by collisions with energetic particles.An upper atmospheric glowdistinct from the aurora,a pale greenish airglow caused bya cascade of chemical reactionsexcited by sunlight,can be traced in diagonal bands at top left.

2023年12月17日:中国念湖上空的双子流星雨-（Geminids over China's Nianhu Lake） 2023年12月17日:中国念湖上空的双子流星雨-（Geminids over China's Nianhu Lake）--原图下载{mtitle title="中国念湖上空的双子流星雨"/}Image Credit & Copyright: Hongyang Luo说明: 这些流星是打那里来的？以在天空的方向来说，源头在双子座。因为这群12月的大流星雨，看似源自双子座内的辐射点，故称为双子流星雨。在三维空间上，从怪异法厄同小行星（3200 Phaethon）剥离出来的沙粒状碎片，沿着特定的轨道绕行太阳，而最靠近地球的轨道区就出现在双子座的前方。也因此，每当地球穿过这颗小行星的轨道时，那些洒落的碎片之辐射点就看似位于双子座内。上面这幅组合自多张摄于数天前的照片之主题影像，记录了超过100颗双子流星雨的明亮流星掠过中国 念湖上方的幽暗夜空。{lamp/}原文：{mtitle title="Geminids over China's Nianhu Lake"/}Image Credit & Copyright: Hongyang LuoExplanation: Where are all of these meteors coming from? In terms of direction on the sky, the pointed answer is theconstellationof Gemini. That is why the major meteor shower in December is known as theGeminids -- because shower meteors all appear to come from aradiant toward Gemini.Three dimensionally, however,sand-sized debrisexpelled from the unusual asteroid 3200 Phaethonfollows a well-defined orbit about our Sun, and the part of the orbit that approaches Earth is superposed in front of the constellation of Gemini.Therefore, when Earth crosses this orbit, theradiant point of falling debris appears in Gemini.Featured here is a composite of many images taken a few days ago through dark skies from Nianhu Lake in China.Over 100 bright meteorstreaks from the Geminids meteor shower are visible.

2023年11月25日:小小行星的极光-（Little Planet Aurora） 2023年11月25日:小小行星的极光-（Little Planet Aurora）--原图下载{mtitle title="小小行星的极光"/}Image Credit &Copyright: Victor Lima说明: 沉浸在阴森绿光中的这颗崎岖小小行星，是美丽瀑布和高耸山峰的家园。不过，它只是地球一隅的投影。11月9日那晚，位在冰岛西部柯克朱费尔（Kirkjufell）山区的数位相机，拍下了这幅以天底为中心的併接环景影像。在这张带着圆形地平线的立体投影图里，摇曳的北极光帘把大地渲染成淡绿的世界，而其中心即为柯克朱费尔山。在11月初，因太阳活动而受到激荡的地球磁层，产生了强烈的磁暴并诱发了明亮的极光。北半球的观星者，不难认出在柯克朱费尔山顶的极光后方之北斗七星。而在右下角，则可见到在这颗小小行星夜空中绽放光芒的紧实昴宿星团，以及木星这颗如假包换的巨行星。{lamp/}原文：{mtitle title="Little Planet Aurora"/}Image Credit &Copyright: Victor LimaExplanation: Immersed in an eerie greenish light, this ruggedlittle planetappears to be home to stunning water falls andan impossibly tall mountain.It's planet Earthof course.On the night of November 9the nadir-centered 360 degree mosaic wascaptured by digital camerafrom theKirkjufell mountain areaof western Iceland.Curtains of shimmering Aurora Borealisor Northern Lights provide the pale greenish illumination.The intense auroral display was caused by solar activity that rockedEarth's magnetospherein early November and produced strong geomagnetic storms.Kirkjufell mountain itself stands at the top of thestereographicprojection's circular horizon.Northern hemisphere skygazers will recognizethe familiar stars of the Big Dipper just above Kirkjufell's peak.At lower rightthe compact Pleiades star clusterand truly giantplanet Jupiter also shinein this little planet's night sky.