宇宙間最大的爆炸（圖）

Astronomers have observed possibly the biggest blast ever seen in the cosmos. When NASA"s SWIFT space observatory first spotted it 10 days ago, observers thought it was a massive star blowing up as a supernova and expected it to fade within hours or even minutes. But the high-energy radiation from the source has shown no sign of dying down, which suggests that astronomers may have caught a star in the process of being ripped to shreds by a black hole.

天文學家們可能觀察到了宇宙間最大的爆炸。十年前美國國家航空航天管理局（NASA）的「雨燕」號太空望遠鏡首次發現該爆炸的時候，觀測人員認為那是一顆大型恆星正在爆炸而形成超新星，他們預計幾個小時甚至幾分鐘之內就會暗淡下來。但是，來自那個爆發源的高能輻射一直沒有逐漸消失的跡象，這表明天文學家們所觀察到的可能是一顆恆星正在被黑洞撕成碎片的過程。

The blast is actually a series of bursts, like a string of firecrackers going off one after another. "We know of objects in our own galaxy that can produce repeated bursts, but they are thousands to millions of times less powerful than the bursts we are seeing," says Andrew Fruchter of the Space Telescope Science Institute in Baltimore, Maryland. "This is truly extraordinary."

此次爆炸實際上是一系列的爆發，就像鞭炮一樣一個接一個地燃放。「我們了解到銀河系的天體可以產生不斷地爆炸，但是那些爆炸的威力比我們正在觀測到的爆炸威力要小几千倍到幾百萬倍，」馬里蘭州巴爾的摩市太空望遠鏡科學研究院的安德魯·弗魯赫特說，「這真是太奇怪了！」

SWIFT"s Burst Alert Telescope detected the source of the bursts on 28 March. The Hubble Space Telescope took an image of the source on 4 April, which located the explosions at the center of a galaxy 3.8 billion light-years away. On the same day, NASA"s Chandra X-ray Observatory took a picture of the source by pointing at it for 4 hours. That image also showed that the source of the bursts was at the center of the galaxy imaged by Hubble.

「雨燕」號上搭載的爆發警示望遠鏡探測到3月28日的系列爆發之源。哈勃太空望遠鏡在4月4日拍到了一張該爆發源的圖像，確定了系列爆炸位於38億光年之外一個星系的中心。同一天，NASA的錢德拉X射線望遠鏡在四個小時的時間裡對準這個爆發源，為其拍下了一張圖像。該圖像也顯示，這個爆發源位於哈勃太空望遠鏡所拍星系的中心。

The position of the source within the galaxy offered a clue that the bursts might be associated with a black hole, as nearly all galaxies have a black hole in the middle. "We think that there is a dormant black hole there that has accreted a lump of matter—probably a star that has fallen into it," says astrophysicist Neil Gehrels, the lead scientist for SWIFT at NASA"s Goddard Space Flight Center in Greenbelt, Maryland.

位於星系中心位置的爆發源供了一個線索：系列爆發可能跟黑洞有關，因為幾乎所有星系的中間都有一個黑洞。「我們認為那裡潛伏著一個黑洞，黑洞吸積了大團的物質，這團物質很可能是落入其中的一顆恆星，」馬里蘭州格林貝爾特市NASA戈達德太空飛行中心的天體物理學家、研究「雨燕」號的首席科學家尼爾·格雷爾斯說。

What could be going on is the following: A star flitting too close to the black hole has been grabbed by its gravitational pull. The star"s gas has been falling into the black hole, causing enormous amounts of energy to be released in the form of high-energy particles shooting out like a jet.

可能發生了如下的情況：一顆恆星飛離那個黑洞太近了，被黑洞的引力捕捉到，恆星的氣體不斷地落入黑洞之中，引起大量的能量以高能粒子的形式釋放出來，射向太空，猶如一股射流。

Although this is not the first time astronomers have witnessed a star being gobbled up by a black hole, the bursts are putting out energy far greater than previously seen. One reason for the extreme brightness could be that the jet of particles shooting out of the black hole is pointing straight at Earth.

儘管這不是天文學家們首次目擊恆星被黑洞吞噬的情況，但是這次的系列爆發正在釋放出來的能量比以往所觀察到的要大得多。這一系列爆發極度明亮的一個原因可能是，從黑洞射出的射流正在徑直地朝著地球的方向而來。

Astronomers all over the world are working round the clock to collect more data on the event, and Hubble is snapping more images of the source. "Some spectra have been taken; there"s a lot more work to be done on how the spectrum changes over time," Gehrels says. "If it really is a star being torn up, then we"d expect it to fade away in the next few days. If it stays bright for several weeks or a month, that would tell us something different. I"m not sure what that would be."

為了更多地搜集該事件的數據資料，全世界的天文學家們正在夜以繼日地工作，哈勃太空望遠鏡正在為這個爆發源拍攝更多的快照。「已經拍到了一些光譜，然而要想弄清光譜是如何隨著時間的推移而發生變化的，還有大量的工作要做，」格雷爾斯說，「如果真是一顆正在被撕碎的恆星，那麼我們預計它在接下來的幾天之內就會逐漸消失；如果持續保持光亮幾周或一個月的時間，那麼就表明存在不同的情況。我還不能確定這屬於什麼樣的情況。」