NGC 4013:透视星系的边缘英文原文

    HST拍下了处于宇宙边缘的这张关于NGC 4013的不寻常的照片。这张照片异常清晰地向我们显示了向外延伸的星际的气体和灰尘,同时,也让我们看清了在照片上方的星系盘。

    NGC 4013就像我们银河系一样,是一个旋涡星系,它处在大熊座离地球约55,000,000光年的地方。如果从上面看上去,它应该像一个圆形的风车,但是,在我们这个位置看上去,NGC 4013正好只能看见它的侧面。虽然NGC 4013处于离我们55,000,000光年的地方,哈勃的视场却容不下整个星系。虽然这张照片很清晰,但却只能让我们看见大约一半的星系。



    当星光穿过富含小微粒(例如地球大气中的分子,还有星系中的星际灰尘)的地方时,光会变暗变红。科学家们通过研究NGC 4013被吸收的星光的总数,估计出了星际物质的总量。个别的云层中含有胜过太阳百万倍的灰尘。

    人们相信,暗星际云是恒星诞生的地方。后来,当那些云层散开之后,由蓝星组成的星团变得清晰可见。NGC 4013在照片中间部分也就是银道面的黑边的前上方,让我们看见了几个所谓的“恒星托儿所”。而照片中特别明亮的几颗星不过是银河系中的几颗星,只不过位置正好在我们视线之内罢了。

    这张哈勃的Heritage照片是由约翰·霍普金斯大学的J. Christopher Howk博士和威斯康欣大学的Blair D. Savage博士于2000年1月拍摄的。拍摄这张照片用了三个滤镜,滤去了星系的核区(位于左上方,在那些明亮的恒星之前)。


名称:NGC 4013
位置(2000):赤经:11h 58m 31.13s
赤纬:+43°56' 50.1"

负责人:约翰·霍普金斯大学的J. Christopher Howk博士和威斯康欣大学的Blair D. Savage博士

颜色/滤镜:红:F814W I
蓝:F450W B
绿:F555W V


   译自 哈勃网站(

NGC 4013: A Galaxy on the Edge
Chinese Version

  NASA's Hubble Space Telescope has snapped this remarkable view of a perfectly "edge-on" galaxy, NGC 4013. This new Hubble picture reveals with exquisite detail huge clouds of dust and gas extending along, as well as far above, the galaxy's main disk. 

  NGC 4013 is a spiral galaxy, similar to our own Milky Way, lying some 55 million light-years from Earth in the direction of the constellation Ursa Major. Viewed pole-on, it would look like a nearly circular pinwheel, but NGC 4013 happens to be seen edge-on from our vantage point. Even at 55 million light-years, the galaxy is larger than Hubble's field of view, and the image shows only a little more than half of the object, albeit with unprecedented detail. 

  Dark clouds of interstellar dust stand out in the picture because they absorb the light of background stars. Most of the clouds lie in the plane of the galaxy, forming the dark band, about 500 light-years thick, that appears to cut the galaxy in two from upper right to lower left. A similar effect can be seen in our own sky. If one views the Milky Way by going well away from city lights, dust clouds in the disk of our own galaxy appear to split the glowing band of the Milky Way in two. 

  When light passes through a volume containing small particles (for example, molecules in the Earth's atmosphere, or interstellar dust particles in galaxies), it becomes fainter and redder. By studying the color and the amount of light absorbed by these distant clouds in NGC 4013, astronomers can estimate the amount of matter in them. Individual clouds contain as much as one million times the amount of mass in our Sun. 

  Dark interstellar clouds are believed to be where new stars are formed. Later, when the dust disperses, the young stars become visible as clusters of blue stars. NGC 4013 shows several examples of these stellar kindergartens near the center of the image, lying in front of the dark band along the galaxy's equator. The extremely bright star near the upper left corner, however, is merely a nearby foreground star belonging to our own Milky Way, which happens to lie in the line of sight to NGC 4013. 

  This Hubble Heritage picture was constructed from Hubble images taken in January 2000 by Dr. J. Christopher Howk (Johns Hopkins University) and Dr. Blair D. Savage (University of Wisconsin-Madison). Images taken through three different filters have been combined into a color composite, covering the region of the nucleus of the galaxy (behind the bright foreground star at the upper left). 

fast facts

About this Object 
Name: NGC 4013 
Object Type: Edge-on Spiral Galaxy 
Position (J2000): R.A. 11h 58m 31.13s
Dec. +43?56' 50.1" 
Constellation: Ursa Major 
Distance: About 17 Mpc (55 million light-years) 
Dimensions: The visible portion of the galaxy is 10.7 kpc (35,000 light-years) along its length.

About the Data 
Instrument: WFPC2 
Exposure Dates: January 25, 2000 
Total Exposure Time: 1.7 hours 
Principal Astronomers: J. C. Howk (Johns Hopkins University) and B. D. Savage (University of Wisconsin-Madison) 

About this Image 
Image credit: NASA and The Hubble Heritage Team (STScI/AURA) 
Release Date: March 1, 2001 1:00 a.m. (EST) 
Colors/Filters: Red: F814W I 
Green: F555W V 
Blue: F450W B


   From Hubble Web(