Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 February 3


Light Echoes from V838 Mon
麒麟座V838星的回光

Credit: NASA and the Hubble Heritage Team (AURA/STScI)
影像提供：NASA and the Hubble Heritage Team (AURA/STScI)

Explanation: What caused this outburst of V838 Mon? For reasons unknown, star V838 Mon's outer surface suddenly greatly expanded with the result that it became the brightest star in the entire Milky Way Galaxy in January 2002. Then, just as suddenly, it faded. A stellar flash like this has never been seen before -- supernovas and novas expel matter out into space. Although the V838 Mon flash appears to expel material into space, what is seen in the above image from the Hubble Space Telescope is actually an outwardly moving light echo of the bright flash. In a light echo, light from the flash is reflected by successively more distant rings in the complex array of ambient interstellar dust that already surrounded the star. V838 Mon lies about 20,000 light years away toward the constellation of the unicorn (Monoceros), while the light echo above spans about six light years in diameter.
说明：是什么造成了麒麟座V838星的这次爆发？因某些未知的原因，麒麟座V838星的外表面突然急剧地扩张，让它成为2002年1月整个银河系内最亮的天体。尔后突然之间它黯淡下来。像类似的恒星闪亮以前从来没有发生过—超新星和新星向空间喷射出物质。尽管麒麟座V838星闪烁看上去也是向空间喷射物质，在上面哈勃太空望远镜拍摄的影像中可以看到，实际上是外表层有一层向外移动的明亮回光。这颗恒星的周围，原来就包着数层结构很复杂的星际尘埃，而回光则是外围气壳反射闪光的现象。麒麟座V838距离我们大约2万光年远，位于麒麟座内，上面影像中的回光直径大约6光年。

[ 本帖最后由 咖啡君 于 2008-2-4 00:08 编辑 ]

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 February 4


A Spider Shaped Crater on Mercury
水星上蜘蛛状陨石坑

Credit: MESSENGER, NASA, JHU APL, CIW
影像提供：MESSENGER, NASA, JHU APL, CIW

Explanation: Why does this crater on Mercury look like a spider? When the robotic MESSENGER spacecraft glided by the planet Mercury last month, it was able to image portions of the Sun's closest planet that had never been seen before. When imaging the center of Mercury's extremely large Caloris Basin, MESSENGER found a crater, pictured above, with a set of unusual rays emanating out from its center. A crater with such troughs has never been seen before anywhere in our Solar System. What isn't clear is the relation of the crater to the radial troughs. Perhaps the crater created the radial rays, or perhaps the two features appear only by a chance superposition -- the topic is sure to be one of future research. MESSENGER is scheduled to fly past Mercury twice more before firing its thrusters to enter orbit in 2011.
说明：为什么水星上的这个陨石坑看起来像只蜘蛛？ 当上个月MESSENGER飞船掠过水星时，拍摄到了这颗离太阳最近行星的影像，而那些都是从未看过的。当拍摄水星中央巨大的卡洛斯盆地时，MESSENGER发现了一个陨石坑，如上图所示，可以看到从它的中心放射出一组奇怪的射线。具有如此低谷的陨石坑在我们太阳系内还从未发现过。陨石坑与辐射状盆地有没有联系现在还不清楚。可能是陨石坑形成了放射状的线条，或者可能是两种特征看上去只是偶然重叠而以—可以确定它将成为未来的研究课题。2011年在MESSENGER飞船点燃推进器进入水星轨道之前，预计它还将飞越水星两次以上。

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 February 13


Elliptical Galaxy NGC 1132
椭圆星系NGC1132
Credit: NASA, ESA, M. West (ESO, Chile), and CXC / Penn. State / G. Garmire, et al.
影像提供：NASA, ESA, M. West (ESO, Chile), 和 CXC / Penn. State / G. Garmire,等。
Explanation: NGC 1132 is one smooth galaxy -- but how did it form? As an elliptical galaxy, NGC 1132 has little dust and gas, and few stars have formed in it recently. Although many elliptical galaxies are in clusters of galaxies, NGC 1132 appears as a large, isolated galaxy toward the constellation of the River (Eridanus). To probe the history of this intriguing trillion-star ball, astronomers imaged NGC 1132 in both visible light with the Hubble Space Telescope and X-ray light with the Chandra X-ray Observatory. In this composite false-color image, visible light is white, while the X-ray light is blue and indicates the unusual presence of very hot gas. The X-ray light also likely traces out the location of dark matter. One progenitor hypothesis is that NGC 1132 is the result of a series of galaxy mergers in what once was a small group of galaxies. NGC 1132 is over 300 million light years away, so the light we see from it today left before dinosaurs roamed the Earth. Many fascinating background galaxies can be seen far in the distance.
说明：NGC1132是一个圆滑的星系—但它是怎么形成的呢？作为一个椭圆星系，NGC1132几乎没有尘埃和气体，最近其内也很少有新形成的恒星。尽管许多椭圆星系存在于星系团内，但NGC1132看上去是波江座内一个巨大而又孤立的星系。为了探索这个其内有着万亿颗恒星的神秘星系球的历史，天文学家利用哈勃太空望远镜的可见光和钱德拉Ｘ射线望远镜的Ｘ射线分别对NGC1132进行拍摄。在这张合成假色影像中，可见光是白色的，而Ｘ射线拍摄到的蓝色象征着那里有异常炽热的气体存在。Ｘ射线同样描绘出了暗物质的位置。一种最初的假说是，NGC1132是一系列星系合并的结果，曾经那里是一小团星系群。NGC1132距离我们3亿多光年远，因此我们今天所看到的光是地球上恐龙盛行前该星系发出的。在遥远的地方还能看到很多绚丽的背景星系。

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 February 14

Long Stem Rosette
长梗玫瑰
Credit & Copyright: Adam Block (Caelum Observatory) and Tim Puckett
影像提供及版权：Adam Block (Caelum Observatory) and Tim Puckett
Explanation: The Rosette Nebula (aka NGC 2237) is not the only cosmic cloud of gas and dust to evoke the imagery of flowers. But it is the one most often suggested as a suitable astronomy image for Valentine's Day. Of the many excellent Rosette Nebula pictures submitted to APOD editors, this view seemed most appropriate, with a long stem of glowing hydrogen gas in the region included in the composition. At the edge of a large molecular cloud in Monoceros, some 5,000 light years away, the petals of this rose are actually a stellar nursery whose lovely, symmetric shape is sculpted by the winds and radiation from its central cluster of hot young stars. The stars in the energetic cluster, cataloged as NGC 2244, are only a few million years old, while the central cavity in the Rosette Nebula is about 50 light-years in diameter. Happy Valentine's Day!
说明：玫瑰星云（也被称为NGC2237）不是宇宙尘埃星云中唯一演变得像花朵图案的星云。但它是最能代表情人节的天文图案。在众多APOD编者拍摄到的美妙玫瑰星云影像中，这张影像是最合适的，在这张合成影像中由一条炽热氢气形成的长梗。星云位于麒麟座巨大分子云的边缘，距离我们大约5,000光年远，而玫瑰的花瓣实际上就是一个恒星孕育场，而其可爱而对称的形状是由于中央年轻炽热恒星团发出的恒星风和放射线侵蚀而成。高能恒星团（被归类为NGC2244）内的恒星年龄只有数百万年，而玫瑰星云中央的空洞直径约50光年。情人节快乐！

[ 本帖最后由 咖啡君 于 2008-2-15 09:10 编辑 ]

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 February 15


Young Stars in the Rho Ophiuchi Cloud
心宿增四星云内的年轻恒星

Credit: NASA JPL-Caltech, Harvard-Smithsonian CfA
影像提供：NASA JPL-Caltech, Harvard-Smithsonian CfA

Explanation: Cosmic dust clouds and embedded newborn stars glow at infrared wavelengths in this tantalizing false-color view from the Spitzer Space Telescope. Pictured is of one of the closest star forming regions, part of the Rho Ophiuchi cloud complex some 400 light-years distant near the southern edge of the pronounceable constellation Ophiuchus. The view spans about 5 light-years at that estimated distance. After forming along a large cloud of cold molecular hydrogen gas, newborn stars heat the surrounding dust to produce the infrared glow. An exploration of the region in penetrating infrared light has detected some 300 emerging and newly formed stars whose average age is estimated to be a mere 300,000 years -- extremely young compared to the Sun's age of 5 billion years.
说明：在这张由斯皮策太空望远镜利用红外波段拍摄的假色影像中，宇宙尘埃云和其内的新星发出光和热。上面影像中是距离我们最近的恒星形成区域之一，它是心宿增四复杂星云的一部分，距离我们大约400光年远，位于易辨认的蛇夫座南边缘附近。在这个距离上估计，这张影像大约有5光年。形成于一大片较冷的氢气分子云中，新星激发了周围的尘埃产生了红外光。经过敏锐的红外光线探测后，发现大约有300颗正在出现和新形成的恒星，平均年龄在估计只有30万年，相对于太阳年龄50亿年来说，它们相当年轻

[ 本帖最后由 咖啡君 于 2008-2-16 22:47 编辑 ]

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 February 18


BLG-109: A Distant Version of our own Solar System
BLG-109：太阳系在遥远宇宙中的一个翻版

Illustration Credit: KASI, CBNU, ARCSEC, NSF
插图提供：KASI, CBNU, ARCSEC, NSF

Explanation: How common are planetary systems like our own? Perhaps quite common, as the first system of planets like our own Solar System has been discovered using a newly adapted technique that, so far, has probed only six planetary systems. The technique, called gravitational microlensing, looks for telling brightness changes in measured starlight when a foreground star with planets chances almost directly in front of a more distant star. The distant star's light is slightly deflected in predictable ways by the gravity of the closer system. Recently a detailed analysis of microlensing system OGLE-2006-BLG-109 has related brightness variations to two planets that are similar to Jupiter and Saturn of our own Solar System. This discovery carries the tantalizing implication that interior planets, possibly including Earth-like planets, might also be common. Pictured above is an artistic conception of how the BLG-109 planetary system might look.
说明：类似我们太阳系的行星系统，在宇宙中普遍吗？或许很常见，因为利用一种新技术已经发现了类似我们太阳系的系统，迄今为止，已经发现6个行星系统。这种新技术被称为微重力透镜，通过测量拥有行星的前景恒星几乎直接通过更遥远恒星的前方时，远方恒星星光亮度会有所变化。遥远恒星发出的星光经较紧密行星系统重力影响后，其经过的轨迹会产生微小的偏离。最近对微重力透镜OGLE-2006-BLG-109进行详细分析后，显示光的亮度变化是通过两颗类似我们太阳系内木星和土星的行星造成。这个发现暗示着其内的行星很可能包含类似地球一样的行星，而且有可能普遍存在。上面的图片是艺术家的概念画，展示了BLG-109行星系统可能的模样。

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 February 19


Columbus Laboratory Installed on Space Station
国际空间站安装了哥伦布实验舱

Credit: STS-122 Crew, Expedition 16 Crew, ESA, NASA
影像提供：STS-122 Crew, Expedition 16 Crew, ESA, NASA

Explanation: The International Space Station (ISS) has been equipped with a powerful new scientific laboratory. The Space Shuttle Atlantis delivered the Columbus Laboratory to the ISS and installed the seven meter long module over the past week. Columbus has ten racks for experiments that can be controlled from the station or the Columbus Control Center in Germany. The first set of experiments includes the Fluid Science Laboratory that will explore fluid properties in the microgravity of low Earth orbit, and Biolab which supports experiments on microorganisms. Future Columbus experiments include an atomic clock that will test minuscule timing effects including those expected by Einstein's General Theory of Relativity. Pictured above, mission specialist Hans Schlegel works on the outside of Columbus. Scientists from all over the world may propose and carry out experiments to be done on the laboratory during its ten year mission.
说明：国际空间站（ISS）已经安装上了一个功能强大的新的科学实验室。亚特兰蒂斯号航天飞机将哥伦布实验室送到了国际空间站上，并在过去的一周里将这个7米长的舱体安装完成。哥伦布上的10个实验框架，从空间站或位于德国的哥伦布控制中心都能控制进行。首批试验仪器包括流体科学实验室，研究在地球低轨道微重力下研究流体特性，以及能进行微生物实验的生物实验室。未来的哥伦布试验仪器还有一台原子钟，将被用来测试爱因斯坦广义相对论对时间的微小影响。上面的影像，任务专家Hans Schlegel正在哥伦布实验舱外操作。在哥伦布的十年使命期间，来自全世界的科学家们都能提出计划并在实验室中完成实验。

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 February 20


Moon Slide Slim
苗条的月球轨迹

Credit & Copyright: Stefan Seip (TWAN)
影响提供及版权：Stefan Seip (TWAN)

Explanation: No special filters - or even a telescope - are required to enjoy a leisurely lunar eclipse. In fact, watched from all over the night side of planet Earth, these regular celestial performances have entertained many casual skygazers. Still, this eye-catching picture of a lunar eclipse may look unfamiliar. To make it, astroimager Stefan Seip set his camera on a tripod and locked the shutter open during the total lunar eclipse of March 3, 2007. The resulting image records the trail of the Moon (and narrower trails of stars) sliding through the night. Reddish hues common during the total phase of a lunar eclipse, are evident along the darker, slimmer portion of the Moon trail. At least part of tonight's lunar eclipse will be visible in clear skies over the Americas, Europe, Africa and western Asia. The eclipse lasts over three hours from start to finish, with about 50 minutes of totality. Tonight's eclipse is the last total lunar eclipse until December of 2010.
说明：不需要特殊的滤镜-甚至是望远镜就能欣赏到美妙的月食景观。事实上，位于地球夜晚面的观测者偶然间就能欣赏到这规则的天体表演。但是，这张引人注目的月食影像看起来比较新奇。为了拍成这样的效果，天文学家Stefan Seip把相机固定在三角架上，在2007年3月3日月全食期间一直保持快门打开着，结果就得到的上面这张影像。最后影像中月球的轨迹（还有较窄的星轨）划过夜空。红色的弧线就是月全食期间的阶段，在月球轨迹上有一段很明显的较暗较瘦的痕迹。美洲，欧洲，非洲和西亚地区的晴朗天空中至少能看到今晚的部分月食。月食从开始到结束将持续3个多小时，全食期间大约50分钟。今晚的月食是2010年12月前最后一次月全食。

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 February 21


Orion's Horsehead Nebula
猎户座马头星云

Credit & Copyright: Victor Bertol
影像提供及版权：Victor Bertol

Explanation: The Horsehead Nebula is one of the most famous nebulae on the sky. It is visible as the dark indentation to the red emission nebula seen just below and left of center in the this photograph. The brightest star on the left is located in the belt of the familiar constellation Orion. The horse-head feature is dark because it is really an opaque dust cloud that lies in front of the bright red emission nebula. Like clouds in Earth's atmosphere, this cosmic cloud has assumed a recognizable shape by chance. After many thousands of years, the internal motions of the cloud will alter its appearance. The emission nebula's red color is caused by electrons recombining with protons to form hydrogen atoms. Also visible in the picture are blue reflection nebulae that preferentially reflect the blue light from nearby stars.
说明：马头星云是天空中最为著名的星云之一，它是这张影像中央左下方红色发射星云里的一块黑暗区域。左侧最亮的恒星位于著名的猎户座腰带上。马头显黑色是因为它实际上是红色明亮发射星云前方的一片不透明的尘埃云。就像地球大气层中的云朵一样，这块宇宙云恰好有我们熟悉的形状。经过数千年后，云层内部的活动将改变它的外观。发射星云显现的红色是由质子再次与电子结合形成氢原子后形成。在照片中还可以看到蓝色的反射星云，优先反射了附近恒星发出的蓝光。

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 February 22


Eclipsed Moonlight
月食光

Credit & Copyright: Jerry Lodriguss (Catching the Light)
影像提供及版权：Jerry Lodriguss (Catching the Light)

Explanation: Moon watchers blessed with clear skies over the Americas, Europe, Africa and western Asia enjoyed a total lunar eclipse this week. Catching eclipsed moonlight, astroimager Jerry Lodriguss offers this view of the inspiring celestial event with the shadowed Moon accompanied by wandering planet Saturn at the left, and bright Regulus, alpha star of the constellation Leo, above. The engaging composite picture was made by combining a filtered, telephoto image of the Moon and surrounding starfield with a telescopic exposure. The combination dramatizes the reddened moonlight while clearly showing the variation of brightness and color in Earth's not-so-dark shadow across the lunar surface.
说明：由于本周美洲，欧洲，非洲和西亚地区天空晴朗，让月球观测者们欣赏到了一次美妙的月全食天象。影像拍摄到了月食期间的月光，天文学家Jerry Lodriguss提供了这张激动人心的天文影像，其中附有阴影的月球左侧伴随着若隐若现的土星，而上方则是狮子座α星轩辕十四。这张迷人的合成影像是通过合成一张经过滤波片拍摄到月球的望远镜影像和一张望远镜拍摄周围星场的影像制作合成。这张合成影像加深了红色的月光，清楚地显示了月表阴影处亮度和色彩的差异。

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 February 25


Dawn of the Large Hadron Collider
大型强子对撞机的曙光

Credit & Copyright: Maximilien Brice, CERN
影像提供及版权：Maximilien Brice, CERN

Explanation: Why do objects have mass? To help find out, Europe's CERN has built the Large Hadron Collider (LHC), the most powerful particle accelerator yet created by humans. This May, the LHC is scheduled to start smashing protons into each other with unprecedented impact speeds. The LHC will explore the leading explanation that mass arises from ordinary particles slogging through an otherwise invisible but pervasive field of virtual Higgs particles. Were high energy colliding particles to create real Higgs bosons, the Higgs mechanism for mass creation may be bolstered. LHC will also look for micro black holes, magnetic monopoles, and explore the possibility that every type of fundamental particle we know about has a nearly invisible supersymmetric counterpart. The LHC@Home project will allow anyone with a home computer to help LHC scientists search archived LHC data for these strange beasts. Pictured above, a person stands in front of the huge ATLAS detector, one of six detectors being attached to the LHC.
说明：为什么物体都有质量？为了找到答案，欧洲粒子物理研究所建造了大型强子对撞机（LHC），它是迄今为止人类创造的最高能粒子加速器。预计今年五月，大型强子对撞机将进行以前所未有的速度开始冲撞质子的试验。大型强子对撞机将主要研究质量的起源，普通微粒猛击另一种不可见但普遍存在的希格斯虚粒子而形成。高能粒子碰撞会形成真正的希格斯波色子，这就对希格斯原理产生质量提供支持。大型强子对撞机还将寻找微型黑洞，磁单极子，以及探索我们所知道的每一类基本微粒是否有一种不可见的超对称微粒存在。LHC@Home工程允许每一位有家用电脑的人来帮助LHC科学家利用这些已经入档的LHC数据寻找那些奇怪的微粒。上面的影像中，一个人站在巨大的ATLAS侦测器前，这是六个侦测器中连接到大型强子对撞机的一个。

[ 本帖最后由 咖啡君 于 2008-2-25 23:02 编辑 ]

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 February 26


Mysterious Acid Haze on Venus
金星上神秘的酸性薄雾

Credit: ESA/MPS, Katlenburg-Lindau, Germany
影像提供：ESA/MPS, Katlenburg-Lindau, Germany

Explanation: Why did an acidic haze spread across Venus? The unusual clouds were discovered last July by ESA's robotic Venus Express spacecraft currently orbiting Venus. The bright and smooth haze was found by Venus Express to be rich in sulfuric acid, created when an unknown process lifted water vapor and sulphur dioxide from lower levels into Venus' upper atmosphere. There, sunlight broke these molecules apart and some of them recombined into the volatile sulfuric acid. Over the course of just a few days last July, the smooth acidic clouds spread from the South Pole of Venus across half the planet. The above false-color picture of Venus was taken last July 23rd in ultraviolet light, and shows the unusual haze as relatively smooth regions across the image bottom. The cause of the dark streaks in the clouds is also not yet understood and is being researched.
说明：为什么酸性薄雾会遍布金星？这片奇特的云是欧空局正绕金星飞行的金星快车探测器在去年7月发现的。金星快车发现明亮而均匀的薄雾中富含硫酸，水蒸汽上升遇到低空中的二氧化硫，经过未知的化学反应，而后上升到金星高层大气中从而形成。在那里，太阳光将部分分子分解，其中一些又重新结合形成会挥发的硫酸。仅仅在去年7月的几天里，这些均匀的硫酸雾就从金星南极点一直蔓延开来，覆盖了半个行星。上面这张金星的假色影像是去年7月23日，在紫外线下拍摄的，在影像底部相对平滑的区域就显示这片奇特的薄雾。影像中云雾里暗纹的成因还未知，正在进一步研究中。

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2008 February 27

  
The Eagle Nebula in Hydrogen Oxygen, and Silicon
在氢，氧和硅元素特征光下拍摄的老鹰星云

Credit & Copyright: IAC, Daniel Lopez
影像提供：IAC, Daniel Lopez

Explanation: Bright blue stars are still forming in the dark pillars of the Eagle Nebula. Made famous by a picture from the Hubble Space Telescope in 1995, the Eagle Nebula shows the dramatic process of star formation. To above picture taken by a 0.8-meter telescope in the Canary Islands captures part of M16, the open cluster of stars that is being created. The high amount of detail in the above image results from it being taken only in specific colors of light emitted by hydrogen, oxygen, and silicon. The bright blue stars of M16 have been continually forming over the past 5 million years, most recently in the famous central gas and dust columns that have been informally dubbed the Pillars of Creation and the Fairy. Light takes about 7,000 years to reach us from M16, which spans about 20 light years and can be seen with binoculars toward the constellation of the Serpent (Serpens).
说明：明亮的蓝色恒星仍不停地在老鹰星云内黑暗气柱中形成。老鹰星云之所以出名是因为哈勃太空望远镜在1995年拍摄的一张影像，其中显示了老鹰星云内恒星生动的形成过程。上面这张影像是在加那利群岛上利用0.8米望远镜拍摄到的部分M16，其中疏散星团正在形成。上面影像中高清晰的画面是因为影像是在氢，氧和硅元素发出的特征光下拍摄的。M16内明亮的蓝色恒星在过去的500万年内陆续的形成，最近，著名的中央气体尘埃柱被戏称为恒星诞生地或是仙女。M16发出的光需要经过大约7,000年时间才能被我们看到，它覆盖大约20光年，在巨蛇座方向上，通过双筒望远镜就能看到它。

[ 本帖最后由 咖啡君 于 2008-2-27 21:59 编辑 ]

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 February 28


ISS: Sunlight to Shadow
国际空间站：白天到黑夜

Credit & Copyright: Till Credner, AlltheSky.com
影像提供及版权：Till Credner, AlltheSky.com

Explanation: Orbiting 400,000 kilometers above the Earth, the Moon slid into Earth's shadow to begin last week's total lunar eclipse. Of course the International Space Station (ISS) slides into Earth's shadow every 90 minutes, the time it takes it to complete one orbit at an altitude of about 400 kilometers. Recorded near sunset on February 7, looking toward the north, this composite of 70 exposures shows the trail of the ISS (with gaps between exposures) as it moved left to right over the city of Tübingen in southern Germany. Beginning in sunlight on the left, the ISS vanishes as it enters Earth's shadow at the far right, above the northeastern horizon. As seen from Tübingen, the passage took about 4 minutes. Clicking on the image will download a time-lapse animation (mpg file) based on the individual exposures that includes a plane flying along the horizon.
说明：位于地球外40万公里轨道上的月球，慢慢地进入了地球的阴影，拉开上周月全食的序幕。当然，国际空间站（ISS）每90分钟就会进入地球阴影，它在大约400公里的高空完成了一次轨道绕行。上面这张影像是在2月7日日落时分向北拍摄的，这张影像经过70张曝光影像合成，其中显示了国际空间站从德国南部城市蒂宾根上空，自左向右移动的轨迹（存在曝光间隔）。国际空间站从左侧阳光能找到的地方开始，慢慢消失在最右方地球阴影内，也就是城市东北方地平线上空。从蒂宾根看去，此次国际空间站通过大约持续4分钟。点击上面的影像就能下载一段由单个影像组成的延时动画（mpg文件），其中沿着地平线有一架飞机飞过。

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2008 February 29


Twelve Lunar Eclipses

12张不同时间的月食


Credit & Copyright: Tunç Tezel (TWAN)

影像提供及版权：Tun? Tezel (TWAN)

Explanation: Welcome to the extra day in the Gregorian Calendar's leap year 2008! To celebrate, consider this grid of lunar eclipse pictures - starting in leap year 1996 and ending with February's eclipse - with the date in numerical year/month/day format beneath each image. Mostly based on visibility from a site in Turkey, the 3x4 matrix includes 11 of the 13 total lunar eclipses during that period, and fills out the grid with the partial lunar eclipse of September 2006. Still, as the pictures are at the same scale, they illustrate a noticeable variation in the apparent size of the eclipsed Moon caused by the real change in Earth-Moon distance around the Moon's elliptical orbit. The total phases are also seen to differ in color and darkness. Those effects are due to changes in cloud cover and dust content in the atmosphere reddening and refracting sunlight into Earth's shadow. Of course, the next chance to add a total lunar eclipse to this grid will come at the very end of the decade.

说明：2008年是闰年，欢迎进入新历的额外一天。为了庆祝今天，特意公布了这张月食影像，其中有从闰年1996年开始直到今年2月的月食照片，月食的时间写在照片下方，以年/月/日的格式表示。照片几乎都来源于土耳其的一个观测站上空拍摄到的可见月食，总共包含这段期间13次月全食中的11次，将它们放在3x4的矩阵内，其中还放了一次在2006年9月发生的月偏食。照片没有缩放，可以清楚地看出月食期间月球的大小有所不同，那是因为月球绕着椭圆轨道运行，产生了地月距离上的差异引起。在颜色及阴影方面，月相图看起来也有些不同，那是由于云层与大气含尘量造成红化以及太阳光折射进入地球的阴影造成。当然，下次将月全食影像放入这里的时间会是在2010年底。

[ 本帖最后由 咖啡君 于 2008-3-1 20:27 编辑 ]

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 March 3

Sand Dunes Thawing on Mars
火星上消融中的沙丘

Credit: HiRISE, MRO, LPL (U. Arizona), NASA
影像提供：HiRISE, MRO, LPL (U. Arizona), NASA

Explanation: What are these strange shapes on Mars? Defrosting sand dunes. As spring now dawns on the Northern Hemisphere of Mars, dunes of sand near the pole, as pictured above, are beginning to thaw. The carbon dioxide and water ice actually sublime in the thin atmosphere directly to gas. Thinner regions of ice typically defrost first revealing sand whose darkness soaks in sunlight and accelerates the thaw. The process might even involve sandy jets exploding through the thinning ice. By summer, spots will expand to encompass the entire dunes. The Martian North Pole is ringed by many similar fields of barchan sand dunes, whose strange, smooth arcs are shaped by persistent Martian winds.
说明：火星上这些奇怪的形状是什么？那是消融中的沙丘。随着火星北半球春天的临近，上面影像中极点附近的沙丘开始慢慢消融了。实际上，二氧化碳和冰水会直接升华为气体，进入稀薄的大气层。冰层较薄的地区最先开始消融，而后露出沙子，影像中那些黑色的沙丘吸收了太阳光并加速了冰层的消融。在这个过程中，通过稀薄的冰层甚至可能会发生气沙喷流。到了夏天，这些斑点扩大，将包围整个丘陵。火星北极被许多类似的弧形沙丘包围着，由于一直不断吹着的火星风侵蚀出了这样奇怪而又平滑的形状。

[ 本帖最后由 咖啡君 于 2008-3-3 23:53 编辑 ]

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 March 4


NGC 6334: The Cat's Paw Nebula
NGC6334：猫掌星云

Credit & Copyright: T. A. Rector (U. Alaska), T. Abbott, NOAO, AURA, NSF
影像提供及版权：T. A. Rector (U. Alaska), T. Abbott, NOAO, AURA, NSF

Explanation: Nebulae are perhaps as famous for being identified with familiar shapes as perhaps cats are for getting into trouble. Still, no known cat could have created the vast Cat's Paw Nebula visible in Scorpius. At 5,500 light years distant, Cat's Paw is an emission nebula with a red color that originates from an abundance of ionized hydrogen atoms. Alternatively known as the Bear Claw Nebula or NGC 6334, stars nearly ten times the mass of our Sun have been born there in only the past few million years. Pictured above, the end of the Cat's Paw nebula was imaged from Mayall 4-Meter Telescope on Kitt Peak, Arizona, USA.
说明：星云因类似人们熟知的形状而闻名，就像猫经常陷入麻烦一样。不过，还没有哪只猫能够创造出天蝎座内巨大的猫掌星云。猫掌星云距离我们5,500光年，是一个发射星云，而那红光是大量被电离了的氢原子发出的。其也被称为熊掌星云或是NGC6334，仅仅在过去的几百万年里，星云内产生了比我们太阳质量大十倍的恒星。上面这张猫掌星云末端的影像是由美国亚利桑那州基特峰国家天文台上的4米口径马亚望远镜拍摄的。

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 March 5


The International Space Station Expands Again
国际空间站再次扩建

Credit: STS-122 Shuttle Crew, NASA
影像提供：STS-122 Shuttle Crew, NASA

Explanation: The developing International Space Station (ISS) has changed its appearance again. Last month, the Space Shuttle orbiter Atlantis visited the ISS and added components that included the Columbus Science Laboratory. The entire array of expansive solar panels is visible in this picture taken by the Atlantis Crew after leaving the ISS to return to Earth. The world's foremost space outpost can be seen developing over the past several years by comparing the above image to past images. Also visible above are many different types of modules, a robotic arm, another impressive set of solar panels, and a supply ship. Construction began on the ISS in 1998.
说明：国际空间站(ISS)的不断扩建再一次改变了它的外观。上月，亚特兰蒂斯号航天飞机造访了国际空间站，并为其增加了组建，其中包括哥伦布科学实验室。在上面影像中可以看到整个宽大的太阳能电池板阵列，影像是亚特兰蒂斯号离开国际空间站返回地球时机组人员拍摄。通过将上面影像与过去拍摄到的国际空间站影像比较，这个太空前哨站在过去数年内被不断地扩建。在上面影像中还可以看到许多不同类型的模块，一条机械臂，另一组太阳能电池板，以及一条补给船。国际空间站开始建设的时间是1998年。

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2008 March 6

Vela Supernova Remnant
船帆座超新星的残余

Credit & Copyright: Robert Gendler
Explanation: The plane of our Milky Way Galaxy runs through this complex and beautiful skyscape. At the northwestern edge of the constellation Vela (the Sails) the 16 degree wide, 30 frame mosaic is centered on the glowing filaments of the Vela Supernova Remnant, the expanding debris cloud from the death explosion of a massive star. Light from the supernova explosion that created the Vela remnant reached Earth about 11,000 years ago. In addition to the shocked filaments of glowing gas, the cosmic catastrophe also left behind an incredibly dense, rotating stellar core, the Vela Pulsar. Some 800 light-years distant, the Vela remnant is likely embedded in a larger and older supernova remnant, the Gum Nebula. The broad mosaic includes other identified emission and reflection nebulae, star clusters, and the remarkable Pencil Nebula.

[ 本帖最后由 咖啡君 于 2008-3-12 10:01 编辑 ]