来源:http://hubblesite.org/newscenter ... es/2008/24/image/a/
http://hubblesite.org/newscenter/archive/releases/2008/24/image/a/format/web_print/
ABOUT THIS IMAGE:NASA's Hubble Space Telescope captures the magnificent starry population of the Coma Cluster of galaxies, one of the densest known galaxy collections in the universe.
The Hubble's Advanced Camera for Surveys viewed a large portion of the cluster, spanning several million light-years across. The entire cluster contains thousands of galaxies in a spherical shape more than 20 million light-years in diameter.
Also known as Abell 1656, the Coma Cluster is over 300 million light-years away. The cluster, named after its parent constellation Coma Berenices, is near the Milky Way's north pole. This places the Coma Cluster in an area unobscured by dust and gas from the plane of the Milky Way, and easily visible by Earth viewers.
Most of the galaxies that inhabit the central portion of the Coma Cluster are ellipticals. These featureless "fuzz-balls" are pale goldish brown in color and contain populations of old stars. Both dwarf, as well as giant ellipticals, are found in abundance in the Coma Cluster.
Farther out from the center of the cluster are several spiral galaxies. These galaxies have clouds of cold gas that are giving birth to new stars. Spiral arms and dust lanes "accessorize" these bright bluish-white galaxies that show a distinctive disk structure.
In between the ellipticals and spirals is a morphological class of objects known as S0 (S-zero) galaxies. They are made up of older stars and show little evidence of recent star formation; however, they do show some assemblage of structure — perhaps a bar or a ring, which may give rise to a more disk-like feature.
This Hubble image consists of a section of the cluster that is roughly one-third of the way out from the center of the cluster. One bright spiral galaxy is visible in the upper left of the image. It is distinctly brighter and bluer than galaxies surrounding it. A series of dusty spiral arms appears reddish brown against the whiter disk of the galaxy, and suggests that this galaxy has been disturbed at some point in the past. The other galaxies in the image are either ellipticals, S0 galaxies, or background galaxies far beyond the Coma Cluster sphere.
The data of the Coma Cluster were taken as part of a survey of a nearby rich galaxy cluster. Collectively they will provide a key database for studies of galaxy formation and evolution. This survey will also help to compare galaxies in different environments, both crowded and isolated, as well as to compare relatively nearby galaxies to more distant ones (at higher redshifts).
译文来源:http://www.phys.ncku.edu.tw/~astrolab/mirrors/apod/apod.html
后发座星系团内部
影像版权: NASA, ESA, Hubble Heritage (STScI/AURA);
感谢: D. Carter (LJMU) et al. and the Coma HST ACS Treasury Team
说明:下图中的天体几乎全是星系。这幅影像中的后发座星系团(Coma Cluster of Galaxies)是现知最致密的星系团，它拥有数千个成员星系。每个星系都和我们的银河系相当，是数十亿颗恒星的家园。和大多数的星系团比起来，后发座星系团算相当邻近的，不过光还是得用上数亿年才能传到我们这里。事实上后发座星系团非常庞大，光要从这端传到另一端也要花上数百万年。上面这张嵌合影像是由哈伯太空望远镜所拍摄的后发座星系团的一部份，借以研究丰富星系团中星系如何形成与演化。后发座星系团及其他星系团内的成员则大多是椭圆星系，虽然影像中有一些明显地是螺旋星系。上图中，左上方较偏蓝的螺旋星系在这张广视野的影像中的左上方也可以看到。往背景看去，穿过宇宙空间，可以看到成千上万毫无关联的星系。
[ 本帖最后由 寻找拉玛 于 2008-6-16 13:01 编辑 ] |
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为什么上传不了图片老是说是无效图片文件?斑竹在哪?帮解决一下。
