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发帖数: 623 | 1 2011年03月25日 来源： 新华网
http://news.xinhuanet.com/world/2011-03/25/c_121229284.htm
一个国际天文学家团队２３日说，发现一颗已知温度最低的褐矮星。它的表面温度
为１００摄氏度左右。
德新社报道，欧洲南方天文台先前利用位于智利的甚大望远镜，观测到一个距离地
球大约７５光年的星系。一个国际天文学家团队后在美国夏威夷用两个天文望远镜观测
，发现这一星系由两颗褐矮星组成。
其中一颗褐矮星表面温度为１００摄氏度左右，仅相当于一杯咖啡或桑拿浴室的热
度。天文学家把这颗褐矮星标记为CFBDSIR 1458+10B，称它是已知“最冷”褐矮星。
相比之下，太阳表面温度则高不少，为５５００摄氏度。
褐矮星是一种“流产恒星”，大小介于普通恒星和行星之间，形成过程与恒星相似
。不过，由于质量太小，褐矮星无法在中心产生足够的压力引发氢核聚变，因而无法像
普通恒星一样发出强烈光线，难以观测。
这颗“最冷”褐矮星相关研究报告将发表在最新一期美国《天体物理学杂志》上。
研究报告第一作者、夏威夷大学天文学研究所的马克尔·刘说：“我们预计，这种
温度的褐矮星具备与先前已知褐矮星不同的特点，与太阳系外行星类似。”
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另一个译文：
http://www.astron.ac.cn/bencandy-3-4691-1.htm
重点：
“这颗恒星可能是至今探测到最冷的褐矮星，进一步模糊了寒冷恒星和灼热行星
之间的界线。”
“这两颗天体相当于木星的大小，但为了更好地确定恒星的质量，这个研究团队计划在十年的时间里绘制双星系统的轨道。”
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http://cosmiclog.msnbc.msn.com/_news/2011/03/23/6324415-brown-d
重点：可能褐矮星与行星界定的定义要改了。
Dwarf vs. planet
But is it a brown dwarf? One definition astronomers use to differentiate between stars, brown dwarfs and planets is mass. Anything below about 13 Jupiter masses doesn't get hot enough or dense enough to fuse anything in its interior, so it considered a planet.
The smaller member of the binary system is estimated to be between six and 15 Jupiter masses. "So, most likely it is below the line, and so by that measure one could call it a planet," Liu said.
"But at the same time, I think most of us (astronomers) feel that the way in which something forms, which is difficult to measure, probably has something to do with the way we should classify them," he added.
And this is without a doubt a binary star system – that is two stars orbiting around a common center of mass. Liu and colleagues think it likely formed as low-mass tail of the star forming process, which is different than the way a gas giant planet forms in a disc of material around a star.
"Even though it formed in a different way, it is very low mass, very little energy is coming out and it is very, very cool," Liu said. "And it is a significant leap over the previous coolest known brown dwarf."
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嗯，记得之前有过类似的情况
http://www.mitbbs.com/article_t/Astronomy/31167855.html |
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