4月23日的这次伽马射线爆发（中间），在时间上几乎跟宇宙本身一样古老。
A Blast From the Deep, Dark Past
| Astronomers have imaged the most distant object ever seen--a star collapsing into a black hole more than 13 billion light-years away. The resulting burst of gamma rays, detected by NASA's SWIFT satellite on 23 April and reported tomorrow in two Nature papers, shows that stars were already forming and dying a mere 600 million years after the big bang. |
天文学家们拍下了所观察到的最为遥远的天体——130亿光年之外的一颗恒星，该恒星正在塌缩成为黑洞，由此产生的伽马射线爆发在4月23日被美国航空航天管理局的“雨燕”号轨道卫星探测到，两篇相关的论文将要报道在明天出版的《自然》杂志上。这次爆发显示，在宇宙大爆炸之后仅仅6亿年的时候，恒星就已经开始陆续地形成和灭亡了。 |
| Every week, astronomers sight two or three gamma ray bursts (GRBs), short flashes of high-energy radiation from collapsing stars. Most turn out to be from the nearby universe. But GRB 090423--named, by convention, after the date it was detected--shatters the previous record for farthest object, a galaxy 12.8 billion light-years away that was discovered in 2006. "It brings us close to that magical point of first light," says Volker Bromm, an astrophysicist at the University of Texas, Austin, who was not involved in the study. "We don't have to get much farther to catch the earliest stars." |
天文学家们每周都能看到两三次伽马射线爆发（GRBs）现象，这种现象是恒星塌缩时产生的高能辐射所造成的短暂闪光。多数伽马射线爆发来自宇宙中的附近之处。根据惯例，GRB 090423是根据此次伽马射线爆发被发现的日期命名的。这项发现在距离上打破了以前的记录——此前，在2006年曾发现过一个位于128亿光年之外的星系。“该发现使我们距离那神奇的第一束光线更近一步了，”德克萨斯大学奥斯汀分校的天体物理学家沃尔克·布罗姆说，“我们不必费很大的周折就能拍摄到最早期的恒星。” |
| Researchers are interested in spotting and studying such far-out objects because they provide a window on the early universe. Theoretical models predict that blobs of gas began collapsing into massive stars within a few hundred million years of the big bang. These stars burned for a while before exploding as supernova. The limited information obtained from GRB 090423's spectra indicates that despite its proximity to the big bang, it does not belong to the first generation of stars, the two teams report. |
研究人员对于发现和研究这样遥远的天体很感兴趣，因为这些天体可以为了解早期的宇宙打开一个窗口。理论模型预测：大爆炸之后的几亿年之内，气团开始塌缩，形成巨型恒星；这些恒星燃烧一段时间之后就会爆炸，成为超新星。两个研究小组报道说：通过GRB 090423的光谱所获得的有限信息表明，尽管这次爆炸在时间上接近宇宙大爆炸，但这颗恒星并不属于第一代恒星。 |
| One team was led by Nial Tanvir of the University of Leicester in the United Kingdom, the other by Ruben Salvaterra of the Italian Institute of Astrophysics in Merate. Soon after the burst was detected by SWIFT, both groups scrambled to observe it before the signal faded away using ground-based telescopes. The story of that race appeared in the 18 September issue of Science. |
一个研究小组由英国莱切斯特大学的尼尔·坦沃尔领导，另一个研究小组由意大利天体物理研究所的鲁宾·萨尔沃泰拉领导。“雨燕”号发现这次爆发之后不久，两个研究小组利用地面望远镜争先恐后地进行观察，直到信号消失。对那次观察竞赛的报道曾经发表在9月18日出版的《科学》杂志上。 |
| Tanvir and his colleagues estimate that the density of stars in the early universe was great enough for astronomers to expect the detection of even more distant GRBs in the future. "Finding such events is not an unreasonable hope," they write, noting that they took the first spectra from GRB 090423 15 hours after the burst. Taking spectra more quickly would have yielded more information about its composition, and that's exactly what researchers aim to do the next time they spot an ancient flare. |
坦沃尔及同事估计：早期宇宙中的恒星密度很高，天文学家们可以期待在未来发现更为遥远的GRBs现象。研究人员注意到GRB 090423爆发15个小时之后所获取的第一批光谱，他们在论文中写道：“有希望发现更为遥远的GRBs事件，这并非无稽之谈。”如果能够更早地获取光谱，就可以揭示有关其构成成分的更多信息，这也正是研究人员下次发现远古爆炸时将要做的事情。 |
