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今年3月份，宇宙半空中的一颗恒星爆发出一股伽马射线喷流，直接射向地球。 A Bright Light Shining Upon Us By Phil Berardelli 胡德良 译
| The incident was so extreme, it almost defies description. In the wee hours of the morning of 19 March, astronomers detected from more than halfway across the universe a burst of gamma rays brighter than a hundred-billion suns--and aimed squarely at Earth. Now, after 6 months of analysis, an international team of astronomers has discovered why the event was so extraordinary. | 这是一个如此极端的事件，简直无法形容。3月19日凌晨时分，天文学家们发现了伽马射线的爆发现象，射线来自宇宙半空之外，比一千亿个太阳还要明亮，径直地射向地球。目前，一个由天文学家构成的跨国研究小组经过6个月的分析之后，发现了这次伽马射线爆发事件为何如此异乎寻常。 | | From brief glimpses throughout the past decade, astronomers have pieced together a standard theory of gamma ray bursts. When massive stars exhaust their nuclear fuel and can no longer resist the relentless, crushing force of gravity, they collapse violently. As a star much more massive than the sun contracts to the size of an asteroid--or even smaller if it becomes a black hole--it creates unimaginable densities, temperatures, and energy. A great deal of that energy rebounds outward in a jet of particles traveling at nearly the speed of light. When that jet meets surrounding gas or dust, it generates gamma rays. | 在过去的整整十年中，天文学家们综合了所瞥见的爆发现象，创建了有关伽马射线爆发的标准理论。当耗尽核燃料的时候，大型恒星再也抵挡不住核心引力造成的残酷的粉碎性重压，它们发生剧烈塌缩。一颗比太阳大许多的恒星塌缩成一颗小行星大小的星体，如果成为黑洞的话，塌缩后会比小行星更小，因而产生了无法想象的高密度、高温和高能，其中大量的能量以粒子喷流的形式向外弹回，以接近光速的速度穿行于宇宙空间。当这种喷流遇到周围的气体或尘埃的时候，伽马射线就产生了。 | | New details are revising that picture. A team of 93 scientists report tomorrow in Nature that the "naked eye" burst from March--originating in a galaxy about 7.5 billion light-years away in the direction of the constellation Bootes--shows a feature that has never been seen before. After analyzing data from NASA's Swift spacecraft, which was designed to move very quickly in the direction of gamma radiation, and other data from both satellite and ground-based telescopes and detectors, the team says the super bright beam was surrounded by a less energetic, slower jet about 20 times wider. This could mean, the team suggests, that a bright, narrow beam accompanies all gamma ray bursts but can't be spotted unless it is aimed directly at Earth. | 然而，新发现的详情正在使上述画面有所改动。由93名科学家组成的研究小组在明天出版的《自然》杂志上报道：3月份，“肉眼可见”的伽马射线爆发起源于75亿光年以外的一个星系中，该星系处于牧夫座的方向上；这次伽马射线爆发呈现出以前从未见过的特点。美国国家航空航天管理局“雨燕”号太空船的设计目的就是为了神速地对准伽马射线射来的方向。对“雨燕”号太空船的数据资料，以及对其他太空和地面望远镜与探测器的数据资料进行分析之后，研究小组称：这个超级明亮的光束周围是能量较低的、速度较慢的喷流，其宽度是约光束的20倍。研究小组提出：这有可能意味着，明亮的细光束伴随着所有的伽马射线，但是其方向若不是直指地球，是不会被发现的。 | | Events such as the naked-eye burst "are cracking away at the simple picture" theorists have assembled over the past decade, says astrophysicist Joshua Bloom of the University of California, Berkeley. Moreover, this incident could constitute the first of a remarkable series of glimpses into the most distant parts of the universe, he says. The burst was so bright, Bloom explains, that it could be observed with relatively small telescopes--and even with the naked eye. If astronomers get lucky again, they might spy similar bursts from even farther away, perhaps among the very earliest stars. | 加州大学伯克利分校的天体物理学家乔舒亚·布卢姆指出，在理论学家们利用过去十年的资料所拼凑起来的那幅简单画面中，肉眼可见的爆发事件是不存在的。他说：况且，在对最遥远的宇宙天区进行的一系列引人注目的观测中，该事件可以算得上是首屈一指的。布卢姆解释说，这次爆发极为明亮，利用相对小型的望远镜就可以观察到，甚至用肉眼都可以观察到。如果再次拥有好运气的话，天文学家们会发现来自更远处的类似爆发，这种爆发可能会来自一颗最早的恒星。 |
译自：美国《科学》杂志网站（10 September 2008）
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