探索宇宙! 每天发布一张有专业天文学家的简短解释和说明的反映我们迷人宇宙的不同影像或照片。

                          2008 January 10



Active Galaxy Centaurus A
活动星系半人马座A

Credit: X-ray - NASA, CXC, R.Kraft (CfA), et al.;
Radio - NSF, VLA, M.Hardcastle (U Hertfordshire) et al.; Optical - ESO, M.Rejkuba (ESO-Garching) et al.


影像提供：X射线 - NASA, CXC, R.Kraft (CfA), et al.;
射电- NSF, VLA, M.Hardcastle (U Hertfordshire) et al.; 可见光 - ESO, M.Rejkuba (ESO-Garching) et al.

Explanation: A mere 11 million light-years away, Centaurus A is a giant elliptical galaxy - the closest active galaxy to Earth. This remarkable composite view of the galaxy combines image data from the x-ray ( Chandra), optical(ESO), and radio(VLA) regimes. Centaurus A's central region is a jumble of gas, dust, and stars in optical light, but both radio and x-ray telescopes trace a remarkable jet of high-energy particles streaming from the galaxy's core. The cosmic particle accelerator's power source is a black hole with about 10 million times the mass of the Sun coincident with the x-ray bright spot at the galaxy's center. Blasting out from the active galactic nucleus toward the upper left, the energetic jet extends about 13,000 light-years. A shorter jet extends from the nucleus in the opposite direction. Other x-ray bright spots in the field are binary star systems with neutron stars or stellar mass black holes. Active galaxy Centaurus A is likely the result of a merger with a spiral galaxy some 100 million years ago.

说明：巨大的椭圆星系半人马座A距离我们近1,100光年远，也是距离地球最近的活动星系。这张壮观的合成影像中，合成星系影像的数据分别来自X射线（钱德拉），可见光（ESO），和射电（VLA）下拍摄得到。在可见光下，半人马座A的中心区域由气体、尘埃以及恒星混合而成，但在射电和X射线望远镜下都能看到从星系核内喷射出一道壮观的高能微粒喷流。宇宙微粒加速器的能量源是一个黑洞，质量大约是太阳的1,000万倍，就是X射线下星系核中央的蓝点。高能喷流从活动星系核喷向影像左上方，一直延长大约有1.3万光年远。而从星系核爆发的另一个较小的喷流朝向反方向。在这片区域中，其它X射线下的亮点是拥有中子星和黑洞的双星系统。活动星系半人马座A可能是1亿年前与一个旋涡星系合并而成。0

[ 本帖最后由 咖啡君 于 2008-7-23 00:39 编辑 ]

图片来源:每日天文一图(NASA主站)  

译文来源每日天文一图(北京天文馆分站)
Polaris Dust Nebula
北极星尘埃星云

Image Credit & Copyright: Steve Mandel (Hidden Valley Observatory)
Research Collaboration: Adolf Witt (University of Toledo) et al.
影像提供及版权：Steve Mandel (Hidden Valley Observatory)
合作研究：Adolf Witt (University of Toledo) et al.

Explanation: Centered on North Star Polaris, this 4 degree wide field of view covers part of a complex of relatively unfamiliar, diffuse dust clouds soaring high above the plane of our Milky Way Galaxy. The combined light of the Milky Way stars are reflected by the dusty, galactic cirrus, the reflected starlight having the same blue tint characteristic of better known reflection nebulae. But this deep color image also records a faint reddish luminescence from the dust grains as they convert invisible stellar ultraviolet radiation to visible red light. Dubbed extended red emission, the dim cosmic glow is thought to be caused by complex organic molecules known as PAHs (polycyclic aromatic hydrocarbons), common constituents of interstellar dust. On planet Earth, PAHs are widely encountered as the sooty products of combustion.
说明：在这张宽4度的广域影像中，中心是北极星，还包含了部分相对生疏且较模糊的复杂尘埃云，高高地漂浮在我们银河系盘面上。银河系恒星发出的光经过尘埃，星系卷云反射后混合在一起，反射星光有一种同样的特征色彩，它们被称为反射星云。但是在这张颜色深暗的影像中，还拍摄到从尘埃发出的昏暗而又略带红色的发光带，它们将不可见的恒星紫外线转变成了可见的红光。那暗淡的宇宙光热被称为广延红色辐射，其被认为是复杂有机分子多环芳烃PAHs，它也是普通的星际尘埃组成成分。在地球上，燃烧之后经常能出现焦黑色的产物那就是多环芳烃。

   


[ 本帖最后由 咖啡君 于 2008-1-25 11:11 编辑 ]

探索宇宙! 每天发布一张有专业天文学家的简短解释和说明的反映我们迷人宇宙的不同影像或照片。 2008 年 01 月 12 日

Mercury Chases the Sunset
追逐落日的水星

Image Credit & Copyright: Doug Zubenel
Explanation: This colorful view of the western sky at sunset features last Wednesday's slender crescent Moon. Of course, when the Moon is in its crescent phase it can never be far from the Sun in the sky. Also always close to the Sun in Earth's sky is innermost planet Mercury, seen here below and right of center against the bright orange glow along the horizon. Mercury is usually difficult to glimpse because of overwhelming sunlight, but increasingly better views of the small planet after sunset will be possible as it wanders farther east of the Sun in the coming days. On January 14th, NASA's MESSENGER spacecraft will have a good view too, as it makes its first Mercury flyby. 2008 年 01 月 13 日
Hurricane Ivan from the Space Station
来自太空站的飓风Ivan

Credit: Expedition 9 Crew, International Space Station, NASA
Explanation: Ninety percent of the houses on Grenada were damaged by the destructive force of Hurricane Ivan. At its peak, Ivan was a Category 5 hurricane, the highest power category on the Saffir-Simpson Scale, and created sustained winds in excess of 200 kilometers per hour. Ivan was the largest hurricane to strike the US in 2004, and, so far, the 10th most powerful in recorded history. As it swirled in the Atlantic Ocean, the tremendous eye of Hurricane Ivan was photographed from above by the orbiting International Space Station. The name Ivan has now been retired from Atlantic Ocean use by the World Meteorological Organization. Note: Astronomy lectures by an APOD editor are now available as a free podcast.

[ 本帖最后由 咖啡君 于 2008-1-18 13:42 编辑 ]

探索宇宙! 每天发布一张有专业天文学家的简短解释和说明的反映我们迷人宇宙的不同影像或照片。

2008 年 01 月 14 日

The Cocoon Nebula from CFHT

CFHT望远镜下的茧状星云
Credit & Copyright: Jean-Charles Cuillandre (CFHT), Hawaiian Starlight, CFHT

影像提供及版权：Jean-Charles Cuillandre (CFHT), Hawaiian Starlight, CFHT

Explanation: What creates the colors of the Cocoon Nebula? The Cocoon Nebula, cataloged as IC 5146, is a strikingly beautiful nebula located about 4,000 light years away toward the constellation of the Swan (Cygnus). Inside the Cocoon Nebula is a newly developing open cluster of stars. Like other stellar nurseries, the Cocoon Nebula holds, at the same time, a bright red emission nebula, blue reflection nebulas, and dark absorption nebulas. Given different mixtures, these three processes create a host of colors in this image taken recently by the Canada-France-Hawaii Telescope (CFHT) in Hawaii, USA. Speculation based on recent measurements holds that the massive star towards the left of the picture opened a hole in an existing molecular cloud through which much of the glowing material flows. The same star, which formed about 100,000 years ago, now provides the energy source for much of the emitted and reflected light from this nebula.
说明：茧状星云的颜色是由什么形成的？茧状星云被编录为IC5146，是距离我们大约4,000光年远，位于天鹅座内的一个美丽而壮观的星云。茧状星云内部有一个正新形成的疏散星团。就像其它恒星孕育场一样，茧状星云同时具有明亮的红色发射星云，蓝色的反射星云以及黑暗的吸收星云的角色。星云不同的形成过程能释放出不同的混合物质，这就形成了这张影像中众多的颜色，影像是由位于美国夏威夷上的加拿大-法国-夏威夷望远镜（CFHT）近期拍摄。基于最近探测得到的数据推测，影像左侧大质量恒星在分子云中打开了一个洞，而炽热物质从中流出。诞生于10万年前的那颗恒星现今正为星云内发出的放射光和反射光提供能源。　

2008 年 01 月 15 日

Double Supernova Remnants DEM L316
双超新星遗迹DEM L316

Credit & Copyright: Gemini Observatory, GMOS-South, NSF
影像提供及版权：Gemini Observatory, GMOS-South, NSF

Explanation: Are these two supernova shells related? To help find out, the 8-meter Gemini Telescope located high atop a mountain in Chile was pointed at the unusual, huge, double-lobed cloud dubbed DEM L316. The resulting image, shown above, yields tremendous detail. Inspection of the image as well as data taken by the orbiting Chandra X-Ray Observatory indicate how different the two supernova remnants are. In particular, the smaller shell appears to be the result of Type Ia supernova where a white dwarf exploded, while the larger shell appears to be the result of a Type II supernova where a massive normal star exploded. Since those two stellar types evolve on such different time scales, they likely did not form together and so are likely not physically associated. Considering also that no evidence exists that the shells are colliding, the two shells are now hypothesized to be superposed by chance. DEM L316 lies about 160,000 light years away in the neighboring Large Magellanic Cloud (LMC) galaxy, spans about 140 light-years across, and appears toward the southern constellation of the Swordfish (Dorado).
说明：这两个超新星遗迹相互间有关系吗？为了找出答案，位于智利山顶上的８米双子望远镜指向了这个奇特，巨大而又具有双瓣的DEM L316。上面显示的影像，收获了大量重要的信息。仔细检查这张影像，同时查看钱德拉X射线天文台拍摄的数据来看两个超新星遗迹有什么不同。特别是，较小的遗迹好像是Ⅰ类超新星爆发的结果（白矮星爆炸），而较大的那个遗迹好像是Ⅱ类超新星爆发的结果（一颗普通大质量恒星爆炸）。因为两颗恒星类型在不同时间段演变，所以它们应该不是同时形成，在物理空间上是没有联系。而且没有证据表明两个遗迹发生碰撞，它们只是碰巧在我们的视线方向上重叠。DEM L316位于距离我们大约16万光年远的大麦哲伦星系内，大小约140光年，位于南方星座剑鱼座内。

[ 本帖最后由 咖啡君 于 2008-1-25 11:17 编辑 ]

探索宇宙! 每天发布一张有专业天文学家的简短解释和说明的反映我们迷人宇宙的不同影像或照片。
2008 年 01 月 16 日


MESSENGER Passes Mercury

MESSENGER飞船靠近水星

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

Explanation: Two days ago, the MESSENGER spacecraft became only the second spacecraft in human history to swoop past Mercury. The last spacecraft to visit the Sun's closest planet was Mariner 10 over 35 years ago. Mariner 10 was not able to photograph Mercury's entire surface, and the images it did send back raised many questions. Therefore, much about planet Mercury remains unknown. This week's flyby of MESSENGER was only the first of three flybys. Over the next few years MESSENGER will swing past twice more and finally enter Mercury's orbit in 2011. MESSENGER is currently moving too fast to enter orbit around Mercury now. The above image was taken two days ago during MESSENGER's flyby and shows part of Mercury's surface that has never been imaged in detail before. Many more MESSENGER will hopefully help scientists better understand how Mercury's surface was formed, and why it is so dense.
说明：两天前，MESSENGER飞船成为人类历史上第二颗掠过水星的探测器。上一艘拜访距离太阳最近行星的飞船是Mariner 10，那已经是35年前的事情了。Mariner 10不能够拍摄下水星整体全貌，而且发回拍摄到的影像都引发了很多疑问。因此，很多关于水星的信息还不清楚。这周MESSENGER的飞越只是计划三次飞越的第一次。在今后的几年里，MESSENGER将会围绕水星旋转两次以上，并最终在2011年围绕水星轨道绕行，但现在MESSENGER运行太快，不能进入水星轨道。这张影像是两天前MESSENGER靠近水星时在上方拍摄的。更多关于水星的详细影像将在今后的几天里传回。MESSENGER收集到的数据能帮助更好的理解水星表面是如何形成，以及为什么水星密度如此致密。

[ 本帖最后由 咖啡君 于 2008-1-25 11:24 编辑 ]

探索宇宙! 每天发布一张有专业天文学家的简短解释和说明的反映我们迷人宇宙的不同影像或照片。
2008 年 01 月 17 日


Thor's Emerald Helmet

雷神的翡翠头盔

Credit & Copyright: Robert Gendler
影像提供及版权：Robert Gendler

Explanation: This helmet-shaped cosmic cloud with wing-like appendages is popularly called Thor's Helmet. Heroically sized even for a Norse god, Thor's Helmet is about 30 light-years across. In fact, the helmet is actually more like an interstellar bubble, blown as a fast wind from the bright, massive star near the bubble's center sweeps through a surrounding molecular cloud. Known as a Wolf-Rayet star, the central star is an extremely hot giant thought to be in a brief, pre-supernova stage of evolution. Cataloged as NGC 2359, the nebula is located about 15,000 light-years away in the constellation Canis Major. The sharp image captures striking details of the nebula's filamentary structures and also records an almost emerald color from strong emission due to oxygen atoms in the glowing gas.
说明：这个带着羽翼，头盔形状的宇宙星云被称为雷神的头盔。该头盔大约30光年宽，对于北欧神话中的雷神来说已经很壮观了。事实上，这个头盔更像一个星际泡泡，从泡泡中央附近明亮，大质量恒星吹出了一道高速风，扫过了周围的分子云。这颗中央星被归类为沃夫-拉叶型恒星，是一颗极度炽热的巨星，正处在短暂且快速变化的前超新星演化阶段。这块被编录为NGC 2359的星云，位于大犬座内，距离我们大约有1.5万光年远。这张清晰的影像捕捉到了这个星云精彩的丝状结构，也记录了发光云气中由氧原子所发出的明亮翠绿色辐射。

[ 本帖最后由 咖啡君 于 2008-1-25 11:26 编辑 ]

探索宇宙! 每天发布一张有专业天文学家的简短解释和说明的反映我们迷人宇宙的不同影像或照片。
2008 年 01 月 18 日  



Supernova Factory NGC 2770

NGC2770内的超新星  

Credit: A. de Ugarte Postigo (ESO) et al., Dark Cosmology Centre (NBI, KU),
Instituto de Astrofísica de Andalucía (CSIC), University of Hertfordshire
影像提供：A. de Ugarte Postigo (ESO) et al., Dark Cosmology Centre (NBI, KU),
Instituto de Astrofísica de Andalucía (CSIC),University of Hertfordshire

Explanation: The stellar explosions known as supernovae are among the most powerful events in the universe. Triggered by the collapsing core of a massive star or the nuclear demise of a white dwarf, supernovae occur in average spiral galaxies only about once every century. But the remarkable spiral galaxy NGC 2770 has lately produced more than its fair share. Two still bright supernovae and the location of a third, originally spotted in 1999 but now faded from view, are indicated in this image of the edge-on spiral. All three supernovae are now thought to be of the core-collapse variety, but the most recent of the trio, SN2008D, was first detected by the Swift satellite at more extreme energies as an X-ray flash (XRF) or possibly a low-energy version of a gamma-ray burst on January 9th. Located a mere 90 million light-years away in the northern constellation Lynx, NGC 2770 is now the closest galaxy known to host such a powerful supernova event.
说明：超新星爆炸是宇宙中能量最强的恒星爆炸事件。由于大质量恒星核或白矮星致密星核坍塌引发，但一般一个旋涡星系在一个世纪内才会发生一次超新星暴发。但在壮观的旋涡星系NGC2770发生的事件打破了这个常规。在这张影像中，有两颗仍然明亮的超新星，但是在1999年发现的第三颗超新星已经在原本位置上看不到了，其位置就在影像旋臂边缘标明处。三个超新星现在被认为是星核坍塌类型，但是三个超新星中最近发现一颗SN2008D，首次由斯威夫特卫星在1月9日监测到了极高能x射线(XRF)或低能伽马射线爆发．NGC2770位于距离我们大约9千万光年元的天猫座内，是迄今为止拥有如此高能超新星事件最近星系．

[ 本帖最后由 咖啡君 于 2008-1-25 11:30 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 January 19

  

Starry Night Castle
星夜城堡
Credit & Copyright: P-M Hedén
影像提供及版权：P-M Hedén

Explanation: The tantalizing Pleiades star cluster seems to lie just beyond the trees above a dark castle tower in this dramatic view of The World at Night. Recorded earlier this month, the starry sky also features bright star Aldebaran below the Pleiades and a small, faint, fuzzy cloud otherwise known as Comet Holmes near picture center at the top of the field. Starry Night Castle might be an appropriate name for the medieval castle ruin in the foreground. But its traditional name is Mörby Castle, found north of Stockholm, near lake Skedviken in Norrtälje, Sweden.
说明：在这张生动的夜晚影像中，心急的昴星团就位于黑暗城堡上方树木的外侧。这张影像拍摄于本月初，星空中还有明亮的毕宿五，就位于昴星团下方，影像中央上方附近小而昏暗模糊的点就是Holmes彗星。前景中的中世纪城堡应该被命为星夜城堡更为恰当。但它传统的名字为M?rby 城堡，位于瑞典首都斯德哥尔摩北部，Skedviken湖附近。

[ 本帖最后由 咖啡君 于 2008-1-25 11:31 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 January 20


Comet McNaught Over Chile
智利上空的麦克诺特彗星

Credit & Copyright: Stéphane Guisard
影像提供及版权：Stéphane Guisard

Explanation: Comet McNaught was perhaps the most photogenic comet of our time. After making quite a show in the northern hemisphere in early January, the comet moved south and developed a long and unusual dust tail that dazzled southern hemisphere observers. In this image, Comet McNaught was captured one year ago above Chile. The bright comet dominates on the left while part of its magnificent tail spreads across the entire picture. From this vantage point in the Andes Mountains, one looks up toward Comet McNaught and a magnificent sky, across at a crescent moon, and down on clouds, atmospheric haze, and the city lights of Santiago. Comet McNaught has glided into the outer Solar System and is now only visible as a speck in a large telescope. The other spectacular comet of 2007, Comet Holmes, has also faded from easy view.
说明：在我们这个时代，麦克诺特彗星可能是我们所见最上镜的彗星。今年一月初在北半球大放异彩后，该彗星运行到地球南方，形成了一条长而奇特的尘埃尾，让南半球的观测者们大饱眼福。上面这张影像，是一年前在智利拍摄的麦克诺特彗星。明亮的彗星占据了影像左侧部分，它那壮观的彗尾扫过了整张影像。站在安第斯山脉有利的地势上，一人朝向麦克诺特彗星就会看到一片壮观的天空中有一轮新月，在云层和大气层雾霾下就是圣地亚哥城市的灯光。麦克诺特彗星已经飞出我们太阳系，现在只能用专业的大型望远镜才能看到它。2007年其它壮观的彗星还有Holmes彗星，它也已从人们的视野里慢慢退去。

[ 本帖最后由 咖啡君 于 2008-1-25 11:33 编辑 ]

探索宇宙! 每天发布一张有专业天文学家的简短解释和说明的反映我们迷人宇宙的不同影像或照片。
2008 年 01 月 21 日


Mercury's Horizon from MESSENGER

MESSENGER拍摄到的水星地平线

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

Explanation: What would it look like to fly past Mercury? Just such an adventure was experienced last week by the MESSENGER spacecraft during its first flyby of the strange moon-like world nearest the Sun. Pictured above is the limb of Mercury seen by MESSENGER upon approach, from about 1 1/2 Earth diameters away. Visible on the hot and barren planet are many craters, many appeared to be more shallow than similarly sized craters on the Moon. The comparatively high gravity of Mercury helps flatten tall structures like high crater walls. MESSENGER was able to take over 1,000 images of Mercury which will be beamed back to Earth for planetary geologists to study. The robotic MESSENGER spacecraft is scheduled to fly past Mercury twice more before firing its thrusters to enter orbit in 2011.
说明：飞越水星上空那将会是什么样子？就是这样的一次冒险旅行，上周MESSENGER飞船就经历了，它首次飞越了距离太阳最近，类似一颗奇怪月球一样的行星。上面的影像是MESSENGER飞船在上方靠近时拍摄到的部分水星表面，拍摄的距离大约为1.5个地球直径那么远。可以看到这颗炽热而荒凉的星球上有许多陨石坑，许多看上去比相同大小的月球环形山浅。水星相对较高的重力作用让较高的结构如陨石坑壁变得更加平坦。MESSENGER飞船拍摄了1000多张水星形象，都将传回地球让行星地质学家进行研究。MESSENGER飞船预计还将对水星进行2次以上的飞越，直到2011年最终进入水星同步轨道位置。

[ 本帖最后由 咖啡君 于 2008-1-25 11:37 编辑 ]

探索宇宙! 每天发布一张有专业天文学家的简短解释和说明的反映我们迷人宇宙的不同影像或照片。
2008 年 01 月 22 日


Shelf Cloud Over Saskatchewan

萨斯喀彻温省上空的滩云

Credit: Jeff Kerr
影像提供：Jeff Kerr

Explanation: Perhaps it's time to go inside. Such thoughts might occur to people witnessing the approach of an impressive shelf cloud. Shelf clouds are typically seen leading thunderstorms, although they may precede any well defined front of relatively cold air. Shelf clouds differ from roll clouds because shelf clouds are attached to a larger cloud system lurking above. Similarly, shelf clouds differ from wall clouds because wall clouds typically trail storm systems. The above pictured shelf cloud was photographed toward the southwest during a trip crossing the prairies of Saskatchewan, Canada on the Trans-Canada Highway in 2001 August. A rising Sun illuminated the impressive cloud from the east as it advanced from the west.
说明：或许应该是待在室内的时候了。当一块壮观的滩云靠近时，目击者就会有这样的想法。滩云经常位于锋面或是相对较冷的空气之前，通常是雷雨降临的前兆。滩云与滚轴云不同，因为滩云上方紧接着的就是一片巨大的云系。同样，滩云与墙云也有些不同，因为墙云通常尾随着风暴系统之后。上面这张滩云影像是2001年8月，在加拿大萨斯喀彻温省横加高速公路上，朝西南方拍摄到的。当壮观的滩云往西移动时，一轮正升起的太阳从东方照亮了它。

[ 本帖最后由 咖啡君 于 2008-1-25 11:38 编辑 ]

探索宇宙! 每天发布一张有专业天文学家的简短解释和说明的反映我们迷人宇宙的不同影像或照片。
2008 年 01 月 23 日


Orbiting Astronaut Reflects Earth

宇航员头盔中地球倒影

Credit: Clayton C. Anderson, Expedition 15 Crew, NASA
影像提供：Clayton C. Anderson, Expedition 15 Crew, NASA

Explanation: Astronaut self-portraits can be particularly interesting. Visible in the above picture, working in from the outer borders, are the edges of the reflecting helmet of a space suit, modules of the International Space Station (ISS), the Earth, the arms of Expedition 15 astronaut Clay Anderson, and the digital camera used to snap the image. This picture was taken during the shuttle orbiter Endeavour's mission to expand the space station last August. The large curvature of the Earth appearing in the visor reflection is not the true curvature of our spherical Earth, but rather an artifact of the curve of the space helmet. Earth's horizon appears only slightly curved when viewed from the height of the ISS -- approximately 400 kilometers. The next space shuttle mission to the space station is currently expected to take place next month and includes the installation of the scientific Columbus Laboratory.
说明：这张宇航员的自拍像特别有意思。在上面的影像中，从外向内依次是宇航服反射头盔的边缘，国际空间站的模块，地球，第15远征队宇航员Clay Anderson的手臂以及用来拍摄这张照片的数码相机。这张影像是在去年8月奋进号执行空间站扩建使命期间拍摄。头盔反射看到的巨大的地球弯曲度并不是我们球形地球真正的弯曲度，而恰恰反映的是太空中头盔弯曲度。从距离地球大约400公里远的国际空间站上看，地球的地平线看上去只是微微弯曲而已。预计下月，航天飞机将再一次飞往空间站进行使命活动，其中包括装配哥伦比亚科学实验室。

[ 本帖最后由 咖啡君 于 2008-1-25 11:40 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 January 24


Andromeda Island Universe

仙女座宇宙岛

Credit & Copyright: Tony Hallas
Explanation: The most distant object easily visible to the unaided eye is M31, the great Andromeda Galaxy some two and a half million light-years away. But without a telescope, even this immense spiral galaxy - spanning over 200,000 light years - appears as a faint, nebulous cloud in the constellation Andromeda. In contrast, a bright yellow nucleus, dark winding dust lanes, gorgeous blue spiral arms and star clusters are recorded in this stunning telescopic digital mosaic. While even casual skygazers are now inspired by the knowledge that there are many distant galaxies like M31, astronomers seriously debated this fundamental concept only 80 years ago. Were these "spiral nebulae" simply outlying components of our own Milky Way Galaxy or were they instead "island universes" -- distant systems of stars comparable to the Milky Way itself? This question was central to the famous Shapley-Curtis debate of 1920, which was later resolved by observations of M31 in favor of Andromeda, island universe.

说明：我们肉眼能轻易看到最遥远的天体就是M31，也就是巨大的仙女座星系，距离我们大约250万光年远。但是，如果没有一架望远镜，即使是如此巨大的旋涡星系（覆盖约20万多光年）看上去也只是一个位于仙女座内昏暗模糊的星云。与之相反，在这张壮观的望远镜数码影像中有明亮的黄色星系核，黑暗的缠绕尘埃带，绚丽的蓝色旋臂和星系团。现在连刚刚入门的观测者也知道宇宙中有许多类似M31的遥远星系，但是在短短的80年内，天文学家们之间连基础的概念都有很严重的争论。这些“旋涡星系”仅仅是我们银河系简单的外围成员，抑或它们是“宇宙岛”—与银河系相当的遥远恒星系统？而这就是1920年著名的Shapley-Curtis之间争论的话题要点，而后通过对M31的观测发现仙女座星云是一个宇宙岛。

[ 本帖最后由 咖啡君 于 2008-1-25 11:00 编辑 ]

探索宇宙! 每天发布一张有专业天文学家的简短解释和说明的反映我们迷人宇宙的不同影像或照片。

2008 年 01 月 25 日

Winter Night at Pic du Midi

南方山峰上的冬季夜空

Credit & Copyright: Alain Sallez (picdumidi.org), David Romeuf (Université Lyon 1)

影像提供及版权：Alain Sallez (picdumidi.org), David Romeuf (Université Lyon 1)

Explanation: This dreamlike view looking south from the historic mountain top Pic du Midi Observatory combines moonlit domes, a winter night sky, and the snowy peaks of the French Pyrenees. Encroaching on the night, lights from the La Mongie ski resort illuminate the mountain slopes nearby while the glow along the distant horizon is from urban areas in southern France and Spain. The night sky features stars of the constellations Orion and Gemini with a bright planet Mars very near the top edge, left of center. The three prominent domes visible (from left to right) house a 0.6 meter telescope reserved for amateur astronomers, a 1 meter telescope that was used to support the Apollo lunar landing missions, and the new, Sun-watching CLIMSO.

说明：这张梦幻般的影像是在著名的南方山峰天文台向南拍摄得到，其中有月光照亮了的圆顶，冬季夜空，以及法国比利牛斯山脉雪峰。在漆黑的夜晚中，La Mongie 滑雪场发出的光照亮附近的山坡，远处地平线的光芒来自法国南部和西班牙城市。夜空中显示了猎户座和双子座的星空特征，影像上边缘中央左侧位置是明亮的火星。影像中可以看到三个主要的圆顶（从左到右）分别装有专为业余天文爱好者配备的直径为0.6米的望远镜，一架曾被用来服务阿波罗月球登陆使命，直径为1米的望远镜，还有就是新建的太阳观测望远镜CLIMSO。

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 January 28


A Solar Eclipse Painting from the 1700s
18世纪的日食油画

Painting Credit: Cosmas Damian Asam; Digital Image Copyright: Jay Pasachoff
油画版权：Cosmas Damian Asam;数码影像版权：Jay Pasachoff

Explanation: Is this painting the earliest realistic depiction of a total eclipse of the Sun? Some historians believe it is. The above painting was completed in 1735 by Cosmas Damian Asam, a painter and architect famous in early eighteenth century Germany. Clearly drawn is not only a total solar eclipse, but the solar corona and the diamond ring effect visible when sunlight flows only between mountains on the Moon. The person depicted viewing these eclipse phenomena is St. Benedict. Roberta J. M. Olson and Jay Pasachoff have hypothesized that Asam himself may have seen first hand one or all of the total solar eclipses of May 1706, 1724, and 1733. Many facts about our astronomical universe that are taken for granted today have been known -- or accurately recorded -- only during the last millennium. Asam's painting currently hangs in Weltenburg Abbey in Bavaria, Germany.
说明：这张画是最早表现日全食写实作品吗？一些历史学家们相信这点。上面这张画是科斯玛斯.达米安.阿萨姆在1735年完成的作品，他是一位画家也是18世纪早期德国著名的建筑师。很明显画中并不仅仅是日全食，其中还能看到日冕以及当日光刚从月球山峰之间露出时出现的钻石环效应。影像中描述日食的人叫St. Benedict。Roberta J. M. Olson和Jay Pasachoff认为阿萨姆本人可能亲自看到一次或者所有1706年、1724年和1733年发生的日全食。仅仅通过上一个千年，我们已经了解，或是精确地记录许多宇宙间发生的事实。阿萨姆的画现在就挂在德国巴伐利亚州威尔腾堡修道院内。

[ 本帖最后由 咖啡君 于 2008-1-28 23:07 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 January 29


West Valley Panorama from the Spirit Rover on Mars
勇气号火星探测器拍摄到的西谷全景影像

Credit: Mars Exploration Rover Mission, Cornell, JPL, NASA
影像提供：Mars Exploration Rover Mission, Cornell, JPL, NASA

Explanation: What does Mars look like from here? Last September, before hiking across rugged and slippery terrain to reach its winter hibernation point, the robotic Spirit rover climbed a small plateau known as Home Plate and captured the spectacular vista pictured above. Part of the curious flat-topped Home Plate is visible as the light colored landscape across the panorama's foreground. On the image left, visible about eight kilometers in the distance, is Grissom Hill, while on the left foreground is rock strewn Tsiolkovski Ridge. On the right, at about 800 meters distant, is Husband Hill, a feature already explored by Spirit and notable as the highest point visible in the westward looking panorama. In the inset is a close-up of a small protrusion informally dubbed Little Bigfoot, a motionless rock that has drawn some attention for it superficial appearance to a humanoid life form. Tenacious image explorers might locate Little Bigfoot towards the front left of the high resolution panorama. Spirit successfully reached its energy-conserving winter haven in December.
说明：从这里看火星会是什么样子？去年9月，在穿过了高低不平而又光滑的岩层，到达过冬地点前，勇气号探测器爬到了一个名为本垒的小高地上，并且拍摄了上面这张壮观的影像。在这张全景影像的前景中，可以看到颜色较浅的地方就是部分奇怪而顶部平坦的本垒。影像左侧，可以看到8公里远处的Grissom 山丘，而在左侧前景中的是散乱的Tsiolkocski山脊岩石。右侧大约800米远的是Husband山，早已被勇气号探索过，并且是影像向西望去的制高点。而左侧这张插图是一个被戏称为小野人的小突起特写，由于这块静止不动的岩石外表与人的形象相似，从而吸引了很多目光。若果你够坚持的话就能在这张高清晰全景影像中的左前方找到这个小野人岩石。去年12月，勇气号成功地到达了节能较好的过冬地点。

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 January 30


Asteroid 2007 TU24 Passes the Earth
小行星2007TU24通过地球

Credit: Green Bank Radio Telescope, Arecibo Radio Telescope
影像提供：Green Bank Radio Telescope, Arecibo Radio Telescope

Explanation: Asteroid 2007 TU24 passed by the Earth yesterday, posing no danger. The space rock, estimated to be about 250 meters across, coasted by just outside the orbit of Earth's Moon. The passing was not very unusual -- small rocks strike Earth daily, and in 2003 a rock the size of a bus passed inside the orbit of the Moon, being detected only after passing. TU24 was notable partly because it was so large. Were TU24 to have struck land, it might have caused a magnitude seven earthquake and left a city-sized crater. A perhaps larger danger would have occurred were TU24 to have struck the ocean and raised a large tsunami. This radar image was taken two days ago. The Arecibo Radio Telescope in Puerto Rico broadcast radar that was reflected by the asteroid and then recorded by the Byrd Radio Telescope in Green Bank, West Virginia. The resulting image shows TU24 to have an oblong and irregular shape. TU24 was discovered only three months ago, indicating that other potentially hazardous asteroids might lurk in our Solar System currently undetected. Objects like TU24 are hard to detect because they are so faint and move so fast. Humanity's ability to scan the sky to detect, catalog, and analyze such objects has increased notably in recent years.
说明：昨天小行星2007TU24通过地球，没有对地球产生任何危险。这颗宇宙岩石直径估计约250米，刚好在月球轨道外侧滑过。此次小行星通过地球没有什么不寻常，每天都会有小岩石撞击地球，2003年一颗大小像巴士一样的岩石进入了月球轨道，在通过地球之后才被发现。之所以TU24被发现，是因为它太大了。如果TU24撞击地面，那将会形成一次7级地震，并且留下一个城市大小的陨石坑。如果TU24掉进海洋，将会形成一次巨大的海啸，那将造成更大的威胁。这张雷达影像是两天前拍摄的。位于波多黎各的阿雷西博射电望远镜放射出的雷达信号经小行星反射后，被西弗吉尼亚州Green Bank的伯德射电望远镜接收到。合成的影像显示TU24是一个不规则长方形状。TU24只是在3个月前发现的，这就暗示了其它对地球有潜在危险的小行星可能存在于我们太阳系内，只是没被发现。像类似TU24一样的天体很难检测到，因为它们异常昏暗而且运行很快。人类正在搜寻天空，检测，归类，分析这样的天体，在最近几年其数量有显著增加。

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 January 31



Young Star Cluster Westerlund 2
年轻星团Westerlund 2

Credit: X-ray; Y.Nazé, G.Rauw, J.Manfroid (Université de Liège), CXC, NASA
Infrared; E.Churchwell (University of Wisconsin), JPL, Caltech, NASA
影像提供：X-射线；Y.Nazé, G.Rauw, J.Manfroid (Université de Liège), CXC, NASA 红外线；E.Churchwell (University of Wisconsin), JPL, Caltech, NASA

Explanation: Dusty stellar nursery RCW 49 surrounds young star cluster Westerlund 2 in this remarkable composite skyscape from beyond the visible spectrum of light. Infrared data from the Spitzer Space Telescope is shown in black and white, complimenting the Chandra X-ray image data (in false color) of the hot energetic stars within the cluster's central region. Looking toward the grand southern constellation Centaurus, both views reveal stars and structures hidden from optical telescopes by obscuring dust. Westerlund 2 itself is a mere 2 million years old or less, and contains some of our galaxy's most luminous, massive and therefore short-lived stars. The infrared signatures of proto-planetary disks have also been identified in the intense star forming region. At the cluster's estimated distance of 20,000 light-years, the square marking the Chandra field of view would be about 50 light-years on a side.  
说明：在这张用不可见光波段拍摄的显著合成影像中，模糊恒星孕育场RCW49包围着年轻星团Westerlund 2。斯皮策太空望远镜拍摄的红外数据在上面影像中显示黑白色，而钱德拉X射线影像数据（假色）显示了星团中央区域的高能炽热恒星。往巨大的南方星座半人马座看去，上面影像显示的恒星和结构在光学望远镜下都被模糊的尘埃遮蔽了。Westerlund 2本身年龄仅仅只有200万年或者更小，其中包含有我们银河系内一些最亮，大质量恒星，因此也是寿命较短的恒星。在致密的恒星形成区域，已经测定了原行星盘面的红外信号。估计星团距离我们大约2万光年远，而钱德拉拍摄的正方形区域大约有50光年。

[ 本帖最后由 咖啡君 于 2008-1-31 16:48 编辑 ]