哈勃偷窥恒星育儿室英文原文
译:
Jack


  NASA的HST最近往对临近星系的深处进行了观察,并且看到了新恒星的形成时的细节。HST这次的目标是我们银河系的一个小伴星系——小麦哲伦星云中的一个新形成的星团。这张新照片向我们展示了编号为N81的星云中明亮的新星群。

  这些在N81中的大质量的恒星以一个很高的速率在向外抛射物质,它们向外发射出强大的星风和震波,以至于在它周围的星云中挖出了一个“茧”。在照片中两颗最明亮的恒星接近N81的中部,向外界发射出很强的紫外线,使得整个星云渐渐地,从头至尾都发出荧光。

              


  在灼热的气体外边,是由氢分子和灰尘组成的较冷的物质。平时,我们是看不见这些物质的,但是,我们通过星云这个背景可以看见它的一部分,它就像是一条长长的灰尘组成的细线,或者是一个一个很小的椭圆形的结。人们相信,新恒星是由这些冷物质通过引力坍缩形成的。

  利用地基望远镜,我们可以看见它很少的一部分特征,所以,它得到了一个绰号,叫“小斑点”。天文学家们弄不清,是不是在N81中还有一些灼热的恒星,或者是N81是一个名副其实的恒星托儿所,因为它的内部可能含有很多的小质量的恒星。最终,在证明后面一个猜测是正确的时候,哈勃的高清晰度照片帮了大忙。在这张彩色照片中,我们可以看见,在N81内部,有着成千上万的白色炽热的恒星。

  同时,N81让我们有了一个仔细观察大质量恒星形成时狂暴的情形,这些至关紧要的信息强有力地支持了横行形成的学说。在那个星团中,最亮的恒星是我们太阳亮度的300,000倍。天文学家们对小麦哲伦星云中恒星的形成一直和热衷,因为,小麦哲伦星云的化学组成和银河系的不同。所有的金属元素(除了氢和氦以外的元素)的丰度,只有我们银河系的十分之一。

  因此,对N81的研究就为我们提供了一个研究很久以前,在远距离的星系中——也就是说在恒星的核形成比氦更重的元素之前,恒星产生的模型。

  以费迪南·麦哲伦命名的小麦哲伦星云,位于距我们200,000光年的地方,而且,只有在南半球,我们才可以看见它。N81是在1950年由Karl Henize进行的名为“SMC”的观测中看见的第81个星云。后来Karl Henize成为了一名宇航员,他乘NASA的宇宙飞船飞向了太空。

  哈勃的N81的照片是由哈勃行星2号宽视野照相机于1997年9月拍摄的。为了得到氧(OⅢ)和氢(H-α,H-β)的发射的光线,拍摄时,他们用了滤镜。

 

   译自 哈勃网站(http://oposite.stsci.edu

Hubble Peeks into a Stellar Nursery in a Nearby Galaxy
Chinese Version


  NASA's Hubble Space Telescope has peered deep into a neighboring galaxy to reveal details of the formation of new stars. Hubble's target was a newborn star cluster within the Small Magellanic Cloud, a small galaxy that is a satellite of our own Milky Way. The new images show young, brilliant stars cradled within a nebula, or glowing cloud of gas, cataloged as N 81. 
NASA的HST

  These massive, recently formed stars inside N 81 are losing material at a high rate, sending out strong stellar winds and shock waves and hollowing out a cocoon within the surrounding nebula. The two most luminous stars, seen in the Hubble image as a very close pair near the center of N 81, emit copious ultraviolet radiation, causing the nebula to glow through fluorescence. 

  Outside the hot, glowing gas is cooler material consisting of hydrogen molecules and dust. Normally this material is invisible, but some of it can be seen in silhouette against the nebular background, as long dust lanes and a small, dark, elliptical-shaped knot. It is believed that the young stars have formed from this cold matter through gravitational contraction. 

  Few features can be seen in N 81 from ground-based telescopes, earning it the informal nick-name "The Blob." Astronomers were not sure if just one or a few hot stars were embedded in the cloud, or if it was a stellar nursery containing a large number of less massive stars. Hubble's high-resolution imaging shows the latter to be the case, revealing that numerous young, white-hot stars---easily visible in the color picture---are contained within N 81. 

  This crucial information bears strongly on theories of star formation, and N 81 offers a singular opportunity for a close-up look at the turbulent conditions accompanying the birth of massive stars. The brightest stars in the cluster have a luminosity equal to 300,000 stars like our own Sun. Astronomers are especially keen to study star formation in the Small Magellanic Cloud, because its chemical composition is different from that of the Milky Way. All of the chemical elements, other than hydrogen and helium, have only about one-tenth the abundances seen in our own galaxy. 

  The study of N81 thus provides an excellent template for studying the star formation that occurred long ago in very distant galaxies, before nuclear reactions inside stars had synthesized the elements heavier than helium. 

  The Small Magellanic Cloud, named after the explorer Ferdinand Magellan, lies 200,000 light-years away, and is visible only from the Earth's southern hemisphere. N 81 is the 81st nebula cataloged in a survey of the SMC carried out in the 1950's by astronomer Karl Henize, who later became an astronomer-astronaut who flew into space aboard NASA's space shuttle. 

  The Hubble Heritage image of N 81 is a color representation of data taken in September, 1997, with Hubble's Wide Field Planetary Camera 2. Color filters were used to sample light emitted by oxygen ([O III]) and hydrogen (H-alpha, H-beta). 

  N 81 is the target of investigations by European astronomers Mohammad Heydari-Malayeri from the Paris Observatory in France; Michael Rosa from the Space Telescope-European Coordinating Facility in Munich, Germany; Hans Zinnecker of the Astrophysical Institute in Potsdam, Germany; Lise Deharveng of Marseille Observatory, France; and Vassilis Charmadaris of Cornell University, USA (formerly at Paris Observatory). Members of this team are interested in understanding the formation of hot, massive stars, especially under conditions different from those in the Milky Way. 

 

   From Hubble Web(http://oposite.stsci.edu

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