本帖最后由 deepgreen 于 2009-3-5 15:06 编辑
原文： http://www.astronomynow.com/090224Turbulencetriggersbirthofmassivestars.html
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Turbulence triggers birth of massive stars
湍流引发大质量恒星形成
By probing the newborn stars in the constellation Serpens Cauda, scientists using the Submillimeter Array have captured the first moments of massive star formation.
通过探测巨蛇座尾部的新生恒星，科学家们使用亚毫米阵列捕获了大质量恒星诞生之初的情形。
While scientists know the basics of star formation - a cloud of cosmic gas draws itself together, growing hotter and denser until nuclear fusion ignites - how massive star formation is triggered and what determines how many stars form from a single cloud is still a grey area.
科学家们已经了解恒星形成的基本机制-星际气云在自身引力作用下收缩凝聚，温度不断升高，密度不断加大，直到核反应启动。但是大质量恒星的形成是如何被引发的，以及单一星云能形成的恒星数量由什么决定仍是有待探索的灰色区域。
New data from the Submillimeter Array (SMA) is helping astronomers begin to answer these questions. The Harvard Smithsonian Center for Astrophysics (CfA) astronomers studied two dusty regions of star formation in the constellation Serpens Cauda, located 15,000 light years away. One region revealed significant heating, indicating that massive new stars must have already formed. The other region had ample material to form massive stars, but showed little signs of star formation, meaning that it is at one of the earliest stages yet identified in the birth of stars.
在亚毫米阵列(SMA)所获得的新数据的帮助下，天文学家们开始尝试回答这些问题。哈佛大学史密森天体物理中心（CfA）的天文学家们研究了位于15000光年之外巨蛇座尾部的两个富含星际尘埃的恒星形成区域。其中一个区域被发现有明显的热源，这意味着有大质量的恒星早已形成了。另一区域虽然拥有足以形成大质量恒星的物质，却几乎没有恒星形成的迹象，这意味着它处于目前所知的恒星形成的最早阶段之一。
"The SMA enables us to see the dust and gas in the cocoon with amazing details, and to probe the initial stages of massive star formation," says Smithsonian astronomer Qizhou Zhang, who is lead author on the report that has just been accepted for publication in The Astrophysical Journal.
“亚毫米阵列使我们能以令人惊讶的细节观察（星云）茧内的尘埃和气体，并探测到大质量恒星形成初始阶段的情形”，史密森中心的天文学家Qizhou Zhang说道。他是已被天体物理学期刊接受的那篇报告的主要作者。
Another piece of the picture of star formation is gravity, which acts to fragment the contracting cloud of gas and dust into smaller and smaller pieces, creating clusters of stars. Such fragmentation may also inhibit the formation of massive stars. As a result, some theorists propose that massive stars must form from collisions of smaller protostars.
恒星形成的重要因素是引力。在它的作用下，不断收缩的尘埃气体云破碎成越来越小的团块，形成一群群的恒星。这样的破碎过程可能也限制着大质量恒星的形成。因此有些理论家提出大质量恒星必定起源于较小的原恒星之间的碰撞。
There are two forces that counteract gravity to suppress the fragmentation of the cloud: thermal pressure from the heat of protostars, and turbulence, which may allow massive stars to form directly from accretion. Previous work suggested that thermal pressure was the stronger influence, but the new SMA study finds that turbulence is more important, at least at the spatial scales examined.
有两种力可以抵消引力的作用从而抑制星云的破碎：源于原恒星热量的温压，以及湍流--它可能允许大质量恒星通过吸积直接形成。以前的研究认为温压的影响更大，但是基于SMA的新研究发现湍流更为重要，至少在已检测过的空间尺度上如此。
"What's unique about these SMA observations is that we can check some of the hypotheses for massive star formation against the observations for the first time," says Zhang. "Unlike what has been assumed in theoretical models, we found that fragmentation is suppressed in these clouds, not by stellar heating but rather by turbulence."
“基于SMA的观测的特别意义在于，我们第一次可以通过实际观测来检验一些有关大质量恒星形成的假说的正确性，”Zhang说道。“与理论模型里的假设不同的是，我们发现破碎过程在这些星云中被抑制了，不是恒星热量影响而是湍流的影响。”
The team already has planned future studies. "We have just started to understand the initial conditions in distant, massive star-forming regions. A large survey that we have launched with the SMA will, in the near future, reveal the nature of more of such objects," said Thushara Pillai of CfA, a co-author of the report.
他们的团队已经定好下一步的研究计划了。“我们才刚开始了解遥远的大质量恒星形成区域的初始状态。我们已在进行的SMA巡天会在不久的将来揭示更多这类天体的性质，”CfA的Thushara Pillai说道，他是该报告的合著者。 |
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