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楼主: 咖啡君

[天文] [中英对照]每日天文一图专题(更新至2008.08.15 正面的NGC6946)

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 楼主| 发表于 2008-7-16 20:55:19 | 显示全部楼层
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 July 8

In the Heart of the Virgo Cluster
室女座星系团的中心
Credit & Copyright: Günter Kerschhuber (Gahberg Observatory)
影像提供及版权:Günter Kerschhuber (Gahberg Observatory)
Explanation: The Virgo Cluster of Galaxies is the closest cluster of galaxies to our Milky Way Galaxy. The Virgo Cluster is so close that it spans more than 5 degrees on the sky - about 10 times the angle made by a full Moon. With its heart lying about 70 million light years distant, the Virgo Cluster is the nearest cluster of galaxies, contains over 2,000 galaxies, and has a noticeable gravitational pull on the galaxies of the Local Group of Galaxies surrounding our Milky Way Galaxy. The cluster contains not only galaxies filled with stars but also gas so hot it glows in X-rays. Motions of galaxies in and around clusters indicate that they contain more dark matter than any visible matter we can see. Pictured above, the heart of the Virgo Cluster includes bright Messier galaxies such as Markarian's Eyes on the upper left, M86 just to the upper right of center, M84 on the far right, as well as spiral galaxy NGC 4388 at the bottom right.
说明:室女座星系团是距离我们银河系最近的星系团。室女座星系团距离我们如此之近,以至于它在天空中覆盖了5度多的天区――大小约是满月的10倍。而它的中心位于距离我们大约7,000万光年的地方,作为距离我们最近的星系团,室女座星系团内包含超过2,000个星系,而且与我们银河系周围的本地星系团之间产生了显著的引力作用。星系团包含的不仅仅只是富含恒星的星系团,还包括发出x射线的炽热气体。星系团内星系的运动表明那里的暗物质比我们看到的可见物质要多。上面影像拍摄得是室女座星系团的中心,包括明亮的梅西耶星系,比如左上方的马卡林之眼,影像中央右上方的M86,最右边的M84,还有影像右侧底部的旋涡星系NGC4388。

[ 本帖最后由 咖啡君 于 2008-7-16 20:56 编辑 ]
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 楼主| 发表于 2008-7-16 20:57:23 | 显示全部楼层
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 July 9

Planets and Fire by Moonlight
月光下的行星和火焰
Credit & Copyright: Dmitrii Zagorodnov
影像提供及版权:Dmitrii Zagorodnov
Explanation: On July 5th, wandering planets, bright stars, and a young crescent Moon graced western skies after sunset. Arrayed along the solar system's ecliptic plane, the three celestial beacons forming this skyscape's eye-catching line-up with the Moon are Saturn (upper left), then Mars, and finally Regulus, alpha star of the constellation Leo. Of course planet Earth itself lies in the foreground, a scene dominated by the city lights of Santa Barbara, California. The smoky haze hanging over the city is from threatening wild fires still burning along the hill at the right. On Thursday evening, Saturn and Mars can be seen in a much closer pairing or conjunction, separated by only about 3/4 degree on the sky.
说明:7月5日,迷离的行星,明亮的恒星,以及一轮新月优美地出现在日落后的西方天空中。沿着太阳系的黄道盘面排列,这三个天体形成了这张影像中引人注目的风景,与月球排列在一起的是土星(左上),然后是火星,最后是轩辕十四-狮子座α星。当然地球本身位于影像前景中,这就是加利福尼亚州、圣芭芭拉城市灯光的美景。而影像右侧的黑烟弥漫在城市的上空,这是由仍在燃烧中的森林大火造成。在星期四晚上,能看到土星与火星靠得很紧,形成了合,在天空中相互间距离仅仅3/4度。
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 楼主| 发表于 2008-7-16 20:58:43 | 显示全部楼层
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 July 10

Enhanced Color Caloris
色彩增强了的Caloris盆地
Image Credit: Courtesy of Science/AAAS
影像提供:Courtesy of Science/AAAS
Explanation: The sprawling Caloris basin on Mercury is one of the solar system's largest impact basins. Created during the early history of the solar system by the impact of a large asteroid-sized body, the basin spans about 1,500 kilometers and is seen in yellowish hues in this enhanced color mosaic. The image data is from the January 14th flyby of the MESSENGER spacecraft, captured with the MDIS instrument. Orange splotches around the basin's perimeter are now thought to be volcanic vents, new evidence that Mercury's smooth plains are indeed lava flows. Other discoveries at Mercury by NASA's MESSENGER mission include evidence that Mercury, like planet Earth, has a global magnetic field generated by a dynamo process in its large core, and that Mercury's surface has contracted significantly as its core cooled.
说明:水星上的Caloris盆地是太阳系内最大的撞击盆地之一。在太阳系形成早期,由一颗巨大的小行星状天体碰撞而成,这个盆地大小约1,500公里,在这张色彩增强的影像中显黄色。这张影像数据是由1月14日,信使号飞船飞越水星时利用MDIS设备拍摄的。盆地边缘的桔红色斑点被认为是火山口,新的证据表明,水星的平原实际上是熔岩流区域。NASA的信使号使命还有其他发现,包括水星像地球一样具有全球性磁场,从巨大的核心中由一个类似发电机效应产生,当它的核心冷却下来后,水星表面有明显的收缩。
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 楼主| 发表于 2008-7-16 21:35:26 | 显示全部楼层
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 July 11

The Far 3kpc Arm
远三千秒差臂
Illustration Credit: R. Hurt (SSC), JPL-Caltech, NASA
图像提供:R. Hurt (SSC), JPL-Caltech, NASA
Explanation: A major discovery was lurking in the data. By accident, while preparing a talk on the Galaxy's spiral arms for a meeting of the American Astronomical Society, Tom Dame (Harvard-Smithsonian CfA) found it - a new spiral arm in the Milky Way. The arm is labeled in this illustration as the Far 3kpc Arm, located at a distance of 3 kpc (kiloparsecs) or about 10,000 light-years from the galactic center, on the opposite side from the Sun. Along with the Near 3kpc Arm whose presence was known since the mid 1950s, the counterpart inner arms now establish that the galaxy has a simple symmetry. The arms are defined by shocked interstellar gas flowing along both sides of the Milky Way's central bar. Dame and his collaborator Patrick Thaddeus recorded the presence of both inner spiral arms in their radio data tracking emission from carbon monoxide molecules along the galactic plane. How much star formation goes on in the counterpart arms? Despite this depiction of stars and star forming regions along the arms, the last attempt to search for star formation in the Near 3kpc Arm was in 1980 and didn't turn up any. The discovery of the Far 3kpc Arm has renewed interest in this and other questions about the center of the Milky Way.
说明:主要的发现都在影像数据里。正为美国天文协会的一次关于星系旋臂的会议上准备一次会谈时,Tom Dame偶然间(哈佛-史密松恩天文物理中心)发现了它--银河系内新出现的一条旋臂。这条旋臂在这张插图里被标为远三千秒差臂,位于距离星系中央大约三千秒差距,或者1万光年远的地方,与我们太阳相对。沿着自20世纪50年代中期就已经了解其存在的近三千秒差臂看去,在其对应位置上的内旋臂已经形成,星系已经是一个较为简单的对称形状。旋臂是由银河系中心棒两边的星际激冷气体形成。Dame和他的搭档Patrick Thaddeus在沿着银河系盘面方向上,利用一氧化碳分子放射出的射电数据跟踪,同时纪录下了两道内部旋臂。在这对内部旋臂上有多少恒星正在形成呢?尽管这里有旋臂上恒星和恒星形成区域的描述,但是最后一次在近三千秒差臂上寻找恒星形成的最后一次尝试是在1980年,但是没有找到任何结果。远三千秒差臂的发现再一次引起人们的兴趣,并且提出了另外的一些关于银河系中心的问题。

[ 本帖最后由 咖啡君 于 2008-7-16 21:36 编辑 ]
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 楼主| 发表于 2008-7-16 22:01:37 | 显示全部楼层
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 July 12

翻译:咖啡君
NGC 7331 and Beyond
NGC 7331及更远处
Credit & Copyright: Don Goldman, Sierra Remote Observatories
影像和版权提供:Don Goldman, Sierra Remote Observatories
Explanation: Big, beautiful spiral galaxy NGC 7331 is often touted as an analog to our own Milky Way. About 50 million light-years distant in the northern constellation Pegasus, NGC 7331 was recognized early on as a spiral nebula and is actually one of the brighter galaxies not included in Charles Messier's famous 18th century catalog. Since the galaxy's disk is inclined to our line-of-sight, long telescopic exposures often result in an image that evokes a strong sense of depth. The effect is further enhanced in this well-framed view by the galaxies that lie beyond this gorgeous island universe. The background galaxies are about one tenth the apparent size of NGC 7331 and so lie roughly ten times farther away. Their strikingly close alignment on the sky with NGC 7331 occurs just by chance. The visual grouping of galaxies is also known as the Deer Lick Group.
说明:巨大美丽的螺旋星系NGC 7331经常被认为与我们自己的银河类似。在北部大约5千万光年的距离的飞马座,NGC 7331早些时候被认定为一个螺旋星云,而且是未包括在18世纪的查尔斯梅西耶星团星云列表里面的最亮的星系之一。由于这个星系的圆盘倾向我们的直视线,长的望远镜曝光得到的往往是引起强烈深度感效果的图片。这个效果进一步被存在于这个灿烂的岛宇宙之外的星系的充分限定的视野加强。背景星系是NGC 7331视觉大小的十分之一,大约在十倍远之外。它们偶尔会出现在天空中明显的与NGC7331接近形成队列。这组视觉上的星系也被称为Deer Lick Group。
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 楼主| 发表于 2008-7-16 22:03:27 | 显示全部楼层
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 July 13

翻译:咖啡君
A Dark Sky Over Death Valley
死谷上的黑暗天空
Credit: Dan Duriscoe, U.S. National Park Service
影像提供:Dan Duriscoe, U.S. National Park Service
Explanation: This eerie glow over Death Valley is in danger. Scrolling right will show a spectacular view from one of the darkest places left in the continental USA: Death Valley, California. The above 360-degree full-sky panorama is a composite of 30 images taken two years ago in Racetrack Playa. The image has been digitally processed and increasingly stretched at high altitudes to make it rectangular. In the foreground on the image right is an unusually placed rock that was pushed by high winds onto Racetrack Playa after a slick rain. In the background is a majestic night sky, featuring thousands of stars and many constellations. The arch across the middle is the central band of our Milky Way Galaxy. Light pollution is threatening dark skies like this all across the US and the world, and therefore the International Dark-Sky Association and the US National Parks Service are suggesting methods that can protect them.
说明:死谷上方奇异的光芒陷入危险了。向右移动能看到美国大陆剩下的最暗的地方的壮观的景象:死谷,加利福尼亚。上方360度整个天空的全景是由两年前在Racetrack Playa拍的30张照片合成的。这张图像经数字处理,渐增地延伸到高纬度使它成为一个矩形。在图像右侧最显眼的位置,是一个在一场雨后被大风毫不费力地推至Racetrack Playa的不寻常的石头。背景是一个宏伟的夜空,展示了数千的星星和许多星座。穿过中部的拱形是银河系的中央光带。这样的光污染威胁着美国和这个世界的夜空,于是国籍黑暗天空协会和美国国家公园管理局在提出能够保护它们的办法。

[ 本帖最后由 咖啡君 于 2008-7-16 22:05 编辑 ]
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 楼主| 发表于 2008-7-16 22:07:21 | 显示全部楼层
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 July 14

Changes in Angular Mars
火星视角的变化
Credit & Copyright: Richard Bosman
影像提供及版权:Richard Bosman
Explanation: Does Mars always appear the same? No. As both Earth and Mars orbit the Sun, the apparent angular size of Mars changes as viewed from the Earth. Pictured above from Enschede, Holland, Mars was captured in 2007 and 2008 with 30 separate images, all taken with the same magnification. When Earth and Mars are on opposite sides of the Sun, Mars appears relatively small. Conversely, when Earth and Mars are near each other, Mars looms large and bright. The largest Mars has appeared in recent history was the opposition of August 2003. Since Mars is always more distant from the Sun than the Earth, Mars never shows a crescent phase to Earthlings. Visible also in the above images are the north polar cap of Mars, dark and light soil, clouds, and, in the early images, a global dust storm. The next opposition, when Earth again passes near to Mars, will occur in early 2010.
说明:火星始终看起来都一样吗?不是。地球和火星都绕太阳旋转,火星外观视角从地球上看在不断变化。上面的影像是在荷兰恩斯赫德拍摄,分别捕捉到了2007年和2008年火星的30张影像,并且都是以同样的放大倍数拍摄。当地球和火星在太阳的不同面时,火星看上去相对较小。相反地,当地球和火星距离较近,火星看上去就显得很大很明亮。在近期,最大时候的火星出现在2003年8月发生冲的时候。因为火星距离太阳始终比地球远,因此火星不会出现盈亏现象。在上面的影像中还可以看到火星的北极冰帽,色彩深浅不一的土壤,云层,以及在早期相片中的出现的全球性沙尘暴。下一次冲将发生在2010年初,到时候地球将再一次近距离距离通过火星。

[ 本帖最后由 咖啡君 于 2008-7-16 22:10 编辑 ]
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 楼主| 发表于 2008-7-16 22:11:13 | 显示全部楼层
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 July 15

Gas and Dust of the Lagoon Nebula
礁湖星云内的气体和尘埃
Credit & Copyright: Fred Vanderhaven
影像提供及版权:Fred Vanderhaven
Explanation: This beautiful cosmic cloud is a popular stop on telescopic tours of the constellation Sagittarius. Eighteenth century cosmic tourist Charles Messier cataloged the bright nebula as M8, while modern day astronomers recognize the Lagoon Nebula as an active stellar nursery about 5,000 light-years distant, in the direction of the center of our Milky Way Galaxy. Striking details can be traced through this remarkable picture, processed to remove stars and hence better reveal the Lagoon's range of filaments of glowing hydrogen gas, dark dust clouds, and the bright, turbulent hourglass region near the image center. This color composite view was recorded under dark skies near Sydney, Australia. At the Lagoon's estimated distance, the picture spans about 50 light-years.
说明:当望远镜扫过人马座天空时,这块美丽的宇宙云将会成为一道美丽的风景。18世纪天文学家查尔斯.梅西耶将这个明亮的星云编录为M8,而如今的天文学家将礁湖星云认为是一个活跃的恒星孕育场,距离我们大约5,000光年远,处于我们银河系中心方向上。在这张显著的影像中还可以看到详尽的细节,影像经过处理后去掉了恒星,这样就能更好地显示礁湖星云中炽热氢气发出的灯丝状物质的范围,黑暗的尘埃云,以及影像中央附近明亮而喧闹的沙漏状区域。这张彩色合成影像是在澳大利亚悉尼附近的黑夜下拍摄的。据礁湖星云的估计距离,这张影像大约覆盖50光年。
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发表于 2008-7-21 15:10:15 | 显示全部楼层
膜拜。。。。。学习。。。
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发表于 2008-7-21 16:23:06 | 显示全部楼层
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 July 16

Makemake of the Outer Solar System
外太阳系的Makemake
Credit: R. Hurt (SSC-Caltech), JPL-Caltech, NASA
影像提供:R. Hurt (SSC-Caltech), JPL-Caltech, NASA
Explanation: Recently discovered Makemake is one of the largest objects known in the outer Solar System. Pronounced MAH-kay MAH-kay, this Kuiper belt object is only slightly smaller than Pluto, orbits the Sun only slightly further out than Pluto, and appears only slightly dimmer than Pluto. Makemake, however, has an orbit much more tilted to the ecliptic plane of the planets than Pluto. Designated 2005 FY9soon after its discovery by a team led by Mike Brown(Caltech) in 2005, the outer Solar System orb was recently renamed Makemake for the creator of humanity in the Rapa Nui mythology of Easter Island. Additionally, Makemake has been recently classified as a dwarf planetunder the new subcategory plutoid, making Makemake the third cataloged plutoid after Pluto and Eris. Makemake is known to be a world somewhat red in appearance, with spectra indicating it is likely covered with frozen methane. Since no images of Makemake's surface yet exist, an artist's illustration originally meant to depict Sedna has been boldly co-opted above to now illustrate Makemake. A hypothetical moon is visualized above nearly in the direction of our distant Sun.
说明:最近发现的Makemake是迄今未止所知外太阳系最大的天体之一。发音为MAH-kay MAH-kay的这颗柯伊伯带天体只比冥王星略小,其绕太阳的轨道比冥王星轨道略远,而且看上去比冥王星略暗。然而,Makemake轨道面对于黄道的倾斜角度比冥王星还大。Mike Brown (Caltech)带领的小组在2005年发现了它之后,就把它命名为2005FY9,最近这颗外太阳系天体才以复活岛的神话中人类的创造神Makemake名字来重新命名。另外,Makemake最近也被归类为类冥矮行星下的一颗矮行星,这也使得Makemake成为冥王星和闹神星之后第三颗类冥矮行星。Makemake外观偏红色,光谱分析显示它很可能被冰冻的甲烷覆盖。现在还没有关于Makemak的表面影像,上面这张影像是艺术家原本用来描述赛德娜的照片被用来描绘Makemake了。在其附近朝向遥远太阳的方向上还有一颗假想的卫星。


[ 本帖最后由 qazwsxedcrfv 于 2008-7-21 16:33 编辑 ]

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发表于 2008-7-21 19:52:07 | 显示全部楼层
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 July 17

Extra Galaxies
星系大观
Credit & Copyright: Dietmar Hager
影像提供及版权:Dietmar Hager
Explanation: (xxxedit and linkxxx) A careful look at the full field of view for this sharp image reveals a surprising number of galaxies both near and far toward the constellation Ursa Major. The most striking is clearly NGC 3718, the warped spiral galaxy right of center. NGC 3718's faint spiral arms look twisted and extended, its bright central region crossed by obscuring dust lanes. A mere 150 thousand light-years to the left is another large spiral galaxy, NGC 3729. The two are likely interacting gravitationally, accounting for the peculiar appearance of NGC 3718. While this galaxy pair lies about 52 million light-years away, the remarkable Hickson Group 56 can also be seen clustered just below NGC 3718. Hickson Group 56 consists of five interacting galaxies and lies over 400 million light-years away.
说明:仔细观看这张清晰的全景影像,就会发现在大熊座方向上从远及近有大量的星系存在。其中最显著的是清晰的星系NGC3718,这个绕曲的旋涡星系位于影像中央右侧。NGC3718昏暗的旋臂看起来弯曲而且向两边延伸,它明亮的中央区域被模糊的尘埃带贯穿。而距离其左侧15万光年远的地方是另一个旋涡大星系NGC3729。这两个星系间好像存在着相互间的引力作用,因为NGC3718有着奇怪的外观。这对星系距离我们大约5,200万光年远,在影像中还可以看到显著的辛克森56星系群就位于NGC3718的下方。辛克森56星系群包含了5个相互间作用的星系,距离我们超过了4亿光年远。



[ 本帖最后由 qazwsxedcrfv 于 2008-7-22 08:45 编辑 ]
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发表于 2008-7-22 16:54:08 | 显示全部楼层
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 July 18

Jupiter over Ephesus
艾菲索斯上空的木星
Credit & Copyright: Tunç Tezel (TWAN)
影像提供及版权:Tun? Tezel (TWAN)
Explanation: A brilliant Jupiter shares the sky with the Full Moon tonight. Since Jupiter is near opposition, literally opposite the Sun in planet Earth's sky, Jupiter will rise near sunset just like the Full Moon. Of course, opposition is also the point of closest approach, with Jupiter shining at its brightest and offering the best views for skygazers. Recorded late last month, this moving skyscape features Jupiter above the southeastern horizon and the marbled streets of the ancient port city of Ephesus, located in modern day Turkey. At the left is a temple dedicated to the Roman emperor Hadrian. The beautiful night sky also includes the arc of the northern summer Milky Way. Lights on the horizon are from the nearby town of Selçuk. Clicking on the image will download the scene as a panorama.
说明:今晚,明亮的木星将与满月一同闪耀在天空中。因为木星正靠近冲,也就是在地球天空中木星的位置与太阳相对,当日落时木星就会升起,就像一轮满月一样。当然,冲是木星与地球最近的点,此时天空中的木星最亮,对于地球上的观测者来是最佳的观测时机。这张影像是上个月末拍摄的,其中拍摄到东南方地平线上空的木星以及古代港口城市艾菲索斯(位于现在的土耳其)大理石铺设的道路。影像左侧的一座寺庙是为了纪念罗马皇帝Hadrian。美丽的夜空还有一段北半球夏季银河。地平线上的光线来自附近城镇塞尔柱。点击上面这张影像可以下载全景影像。


[ 本帖最后由 qazwsxedcrfv 于 2008-7-22 16:55 编辑 ]

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发表于 2008-7-24 16:53:18 | 显示全部楼层
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 July21

The Colliding Spiral Galaxies of Arp 271
Arp 271内碰撞中的旋涡星系
Credit & Copyright: Gemini Observatory, GMOS-South, NSF
影像提供及版权:Gemini Observatory, GMOS-South, NSF
Explanation: What will become of these galaxies? Spiral galaxies NGC 5426 and NGC 5427 are passing dangerously close to each other, but each is likely to survive this collision. Most frequently when galaxies collide, a large galaxy eats a much smaller galaxy. In this case, however, the two galaxies are quite similar, each being a sprawling spiral with expansive arms and a compact core. As the galaxies advance over the next tens of millions of years, their component stars are unlikely to collide, although new stars will form in the bunching of gas caused by gravitational tides. Close inspection of the above image taken by the 8-meter Gemini-South Telescope in Chile shows a bridge of material momentarily connecting the two giants. Known collectively as Arp 271, the interacting pair spans about 130,000 light years and lies about 90 million light-years away toward the constellation of Virgo. Quite possibly, our Milky Way Galaxy will undergo a similar collision with the neighboring Andromeda Galaxy in about five billion years.
说明:这两个星系将会变成什么样?旋涡星系NGC5426和NGC5427以异常危险的距离通过对方,但双方似乎又幸免遇难。当星系发生碰撞时通常发生的是一个较大的星系吞并了较小的星系。在这张影像中,两个星系大小非常相似,都是具有广阔旋臂和致密星系核的旋涡星系。当星系再经历数千万年的演变之后,尽管在潮汐引力造成的气团内会形成新星,但它们的子星不太可能发生碰撞。仔细检查上面的影像,可以发现在两个巨大的星系之间有一条由物质暂时连接的桥梁,这张影像由位于智利,直径为8米的双子南方望远镜拍摄。二者被合称为Arp271,这对相互间作用的星系对覆盖大约13万光年,距离我们大约9,000光年远,位于室女座内。在今后的50亿年里,我们银河系很可能会与邻近的仙女座星系经历一次类似的碰撞。







[ 本帖最后由 qazwsxedcrfv 于 2008-7-25 09:09 编辑 ]
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发表于 2008-7-25 19:20:30 | 显示全部楼层
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 July 23

High Cliffs Surrounding Echus Chasma on Mars
火星Echus裂谷周围陡峭的悬崖
Credit: G. Neukum (FU Berlin) et al., Mars Express, DLR, ESA
影像提供:G. Neukum (FU Berlin) et al., Mars Express, DLR, ESA
Explanation: What created this great cliff on Mars? Did giant waterfalls once plummet through its grooves? With a four-kilometer drop, this high cliff surrounding Echus Chasma, near an impressive impact crater, was carved by either water or lava. A leading hypothesis is that Echus Chasma, at 100-kilometers long and 10-kilometers wide, was once one of the largest water sources on Mars. If true, water once held in Echus Chasma likely ran over the Martian surface to carve the impressive Kasei Valles, which extends over 3,000 kilometers to the north. Even if initially carved by water, lava appears to have later flowed in the valley, leaving an extraordinarily smooth floor. Echus Chasma lies north of tremendous Valles Marineris, the largest canyon in the Solar System. The above image was taken by the robotic Mars Express spacecraft currently orbiting Mars.
说明:什么造成了火星上如此陡峭的悬崖?曾经有巨大的瀑布从这里倾泻而下?陡峭的悬崖围绕着Echus深谷,落差有4,000公里,而深谷就位于撞击坑附近,由流水或熔岩侵蚀而成。有一种主要假说认为,这长达100公里,宽为10公里的Echus裂谷曾经是火星上最大的水源之一。如果假设成立,曾经Echus裂谷内的水在火星表面流淌,从而侵蚀出了卡塞峡谷,这条峡谷向北一直延伸了3,000多公里。即使先前被水流侵蚀,但看上去后来熔岩还是流过峡谷,让峡谷底部变得异常地平坦。Echus深谷位于巨大的水手峡谷的北部,水手峡谷是太阳系内最大的峡谷。上面的影像是由火星快车飞船最近绕火星飞行时拍摄的。

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发表于 2008-7-25 19:35:02 | 显示全部楼层
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 July 24

When Storms Collide
当风暴相遇
Credit: NASA, ESA, Amy Simon-Miller (Goddard Space Flight Center), N. Chanover (NMSU), G. Orton (JPL)
影像提供:NASA, ESA, Amy Simon-Miller (Goddard Space Flight Center),N. Chanover (NMSU), G. Orton (JPL)

Explanation: These detailed Hubble Space Telescope close-ups feature Jupiter's ancient swirling storm system known as the Great Red Spot. They also follow the progress of two newer storm systems that have grown to take on a similar reddish hue: the smaller "Red Spot Jr." (bottom), and smaller still, a "baby red spot". Red Spot Jr. was seen to form in 2006, while the smaller spot was just identified earlier this year. For scale, the Great Red Spot has almost twice the diameter of planet Earth. Moving horizontally from left to right past the Great Red Spot, Red Spot Jr. clearly went below the larger storm, but the smaller spot was pulled in. Emerging on the right, the baby spot's stretched and now paler shape is indicated by the arrow in the frame from July 8. It is expected that the baby red spot will be pulled back and merge, becoming part of the giant storm system.
说明:这些清晰的哈勃太空特写影像,突出了木星古老的旋涡风暴系统—也被称为大红斑。影像同时还记录下了两个新生风暴系统的演化过程,它们成型之后也有类似的红颜色:较小的“小红斑”(位于底部),还有更小的“幼红斑”。小红斑是在2006年形成的,而幼红斑是在今年年初刚发现。就大小看来,大红斑的直径是地球的两倍。小红斑从左到右在水平方向上运动,在大红斑下通过,而幼红斑被大红斑拉了进去。在7月8日拍摄到的影像中,用箭头所指的就是颜色泛白、形状扭曲了的幼红斑,它位于影像的右侧。科学家们预期幼红斑将再次被大红斑拉回,并最终融合,成为巨大风暴系统的一部分。


[ 本帖最后由 qazwsxedcrfv 于 2008-7-25 19:43 编辑 ]
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发表于 2008-7-27 14:30:19 | 显示全部楼层
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 July 25

Spitzer's M101
斯皮策望远镜下的 M101

Credit: NASA, JPL-Caltech, K. Gordon (STScI) et al.
影像提供:NASA, JPL-Caltech, K. Gordon (STScI) et al.
Explanation: Big, beautiful spiral galaxy M101 is one of the last entries in Charles Messier's famous catalog, but definitely not one of the least. About 170,000 light-years across, this galaxy is enormous, almost twice the size of our own Milky Way Galaxy. M101 was also one of the original spiral nebulae observed by Lord Rosse's large 19th century telescope, the Leviathan of Parsontown. Recorded at infrared wavelengths by the Spitzer Space telescope, this 21st century view shows starlight in blue hues while the galaxy's dust clouds are in red. Examining the dust features in the outer rim of the galaxy, astronomers have found that organic molecules present throughout the rest of M101 are lacking. The organic molecules tracked by Spitzer's instruments are called polycyclic aromatic hydrocarbons (PAHs). Of course, PAHs are common components of dust in the Milky Way and on planet Earth are found in soot. PAHs are likely destroyed near the outer edges of M101 by energetic radiation in intense star forming regions. Also known as the Pinwheel Galaxy, M101 lies within the boundaries of the northern constellation Ursa Major, about 25 million light-years away.
说明:美丽而又巨大的旋涡星系M101是最后几个进入查尔斯.梅西耶著名星云星团表的星系之一,但可以确定它不是最小的一个。该星系大小约17万光年,几乎是我们银河系的两倍。M101也是19世纪罗斯爵士的大型望远镜最初发现的旋涡星云之一,该望远镜曾是帕森镇的巨兽。在这张由21世纪斯皮策太空望远镜用红外波段拍摄的影像中,蓝色辉光是恒星光,而红色表示是星系尘埃云。仔细检查星系外围轮廓的尘埃特征后,天文学家发现在M101其它地方出现的有机分子在这里却很少出现。被斯皮策设备追踪的有机分子被称为多环芳香烃(PAHs)。当然,PAHs是银河系尘埃中很普通的组成成分,在地球的烟灰缸中就能找到。很可能是致密恒星形成区域内放射出的高能射线将M101外围边缘附近的PAHs给摧毁了。M101也被称为风车星系,位于北半球大熊座边界,距离我们大约2,500万光年远。


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发表于 2008-7-29 21:24:05 | 显示全部楼层
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 July 26

Central IC 1805
射电星云IC 1805的中心
Credit & Copyright: Keith Quattrocchi
影像版权提供: Keith Quattrocchi
Explanation: Cosmic clouds seem to form fantastic shapes in the central regions of emission nebula IC 1805. Of course, the clouds are sculpted by stellar winds and radiation from massive hot stars in the nebula's newborn star cluster (aka Melotte 15). About 1.5 million years young, the cluster stars appear on the right in this colorful skyscape, along with dark dust clouds silhouetted against glowing atomic gas. A composite of narrow and broad band telescopic images, the view spans about 15 light-years and includes emission from hydrogen in green, sulfur in red, and oxygen in blue hues. Wider field images reveal that IC 1805's simpler, overall outline suggests its popular name - The Heart Nebula. IC 1805 is located about 7,500 light years away toward the constellation Cassiopeia.
说明:发射星云IC 434中心区的宇宙云气,拥有各种非常奇特的形状。当然,它们是由星云内的新恒星星团(Melotte 15)之恒星风和辐射所雕塑出的。这群年龄只有一百五十万年的星团,位在这张彩色星野影像的右方,在辉光原子云气的衬托下,它的内部还有许黝黑的尘埃云。这张照片是由望远镜窄波段和宽波段影像组合出来的,视野横跨15光年的区域,并记录了来自氢(绿色)、硫(红色)和氧(蓝色)的辐射。更大视野的IC 1805照片,更可看出为何它被叫做心脏星云。心脏星云位于仙后座内,离我们约有七千五百光年远。
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发表于 2008-7-31 16:59:22 | 显示全部楼层
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 July 27

IC 4406: A Seemingly Square Nebula
IC 4406:近乎四方形的星云
Credit: C. R. O'Dell (Vanderbilt U.) et al., Hubble Heritage Team, NASA
影像提供: C. R. O'Dell (Vanderbilt U.) et al., Hubble Heritage Team, NASA

Explanation: How can a round star make a square nebula? This conundrum comes to light when studying planetary nebulae like IC 4406. Evidence indicates that IC 4406 is likely a hollow cylinder, with its square appearance the result of our vantage point in viewing the cylinder from the side. Were IC 4406 viewed from the top, it would likely look similar to the Ring Nebula. This representative-color picture is a composite made by combining images taken by the Hubble Space Telescope in 2001 and 2002. Hot gas flows out the ends of the cylinder, while filaments of dark dust and molecular gas lace the bounding walls. The star primarily responsible for this interstellar sculpture can be found in the planetary nebula's center. In a few million years, the only thing left visible in IC 4406 will be a fading white dwarf star.
说明:一颗圆形的恒星怎么会形成一个方形的星云呢?在探索行星状星云IC 4406C 4406时,这样的疑惑不禁显现出来。证据指出IC 4406可能是个中空的圆柱,只是从我们所在的角度看去,看到的是这个圆柱的侧面,所以就看到了方形的模样。若是从IC 4406的上方往下看,看起来就可能跟环状星云差不多。这张代表色照片,是张结合了哈伯太空望远镜在2001年及2002年所拍的影像。热气体自圆柱两端涌出,由黝西尘埃与分子气体组成的黑色细丝则镶嵌在周围壁上。至于造成这座星际雕塑品的始作俑者,我们可以在行星状星云的中心看到此恒星的尊容。再过几百万年,IC 4406将只剩下一颗凋零的白矮星供世人凭吊。
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发表于 2008-8-2 16:39:37 | 显示全部楼层
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 July 28

SDSSJ1430: A Galaxy Einstein Ring
SDSSJ1430:星系的爱因斯坦环

Credit: A. Bolton (UH/IfA) for SLACS and NASA/ESA
影像提供:A. Bolton (UH/IfA) for SLACS and NASA/ESA
Explanation: What's large and blue and can wrap itself around an entire galaxy? A gravitational lens mirage. Pictured above on the left, the gravity of a normal white galaxy has gravitationally distorted the light from a much more distant blue galaxy. More normally, such light bending results in two discernable images of the distant galaxy, but here the lens alignment is so precise that the background galaxy is distorted into a nearly complete ring. Since such a lensing effect was generally predicted in some detail by Albert Einstein over 70 years ago, such rings like SDSSJ1430 are now know as Einstein Rings. SDSSJ1430 was discovered during the Sloan Lens Advanced Camera for Surveys (SLACS) campaign, an observation program that inspected lens candidates found by the Sloan Digital Sky Survey (SDSS) with the Hubble Space Telescope's ACS. Strong gravitational lenses like SDSSJ1440 are more than oddities -- their multiple properties allow astronomers to determine the mass and dark matter content of the foreground galaxy lenses. Given these determinations, SLACS data has now been used, for example, to show that dark matter fraction increases with overall galaxy mass. The inset images on the right depict, from top to bottom, a computer reconstructed image of what the background blue galaxy really looks like, just the white foreground galaxy, and just the lensed blue background galaxy.
说明:那个蓝色巨大的东西是什么,而且能围绕在整个星系的周围?这是一个引力透镜幻象。上面影像的左侧是一个正常白色星系的重力将更遥远的蓝色星系发出的光引力扭曲后得到的结果。更普遍的情况是,光线的扭曲会让遥远星系形成两张独立的影像,但是在这里透镜排列很精确,以至于背景星系被扭曲后,形成了近似于一个圆环。因为透镜效应是70年前由艾波特.爱因斯坦预言提出,所以SDSSJ1430这样的光环现在被称为爱因斯坦环。SDSSJ1430是在斯隆透镜高级摄像仪观测计划活动期间发现,这是基于斯隆数字巡天和哈伯太空望远镜的ACS相机来寻找透镜候选体的计划。类似SDSSJ1430的强引力透镜有很多古怪的事情,它们的多个特性能让天文学家测定前景星系透镜中物质和暗物质的含量。SLACS的数据现在已经被使用,例如,数据显示随着整个星系质量越大,暗物质比例也就越高。而上面影像右侧的插入图片,从上到下依次是,背景蓝色星系真实看上去的样子,再经过计算机重新处理后的影像、白色的前景星系、以及引力透镜下的蓝色背景星系。
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发表于 2008-8-5 11:31:11 | 显示全部楼层
真的是太漂亮了。
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