萬物簡史 第38期:埃文斯牧師的宇宙(7)

The reason we can be reasonably confident thatsuch an event won't happen in our corner of thegalaxy, Thorstensen said, is that it takes aparticular kind of star to make a supernova in thefirst place.

索爾斯坦森說，有理由相信，這種事情在星系的我們這個(gè)角落里不會(huì)發(fā)生，這是因?yàn)?，首先，形成一顆超新星要有一種特別的恒星。

A candidate star must be ten to twenty times as massive as our own Sun and "we don't haveanything of the requisite size that's that close. The universe is a mercifully big place." Thenearest likely candidate he added, is Betelgeuse, whose various sputterings have for yearssuggested that something interestingly unstable is going on there. But Betelgeuse is fiftythousand light-years away.

恒星非得要有我們的太陽10-20倍那么大小才有資格，而"我們附近沒有任何符合這個(gè)條件的星球"。非常運(yùn)氣，宇宙是個(gè)大地方。他接著說，離我們最近的、很可能有資格的，是獵戶座;多年來，它一直在噴出各種東西，表明那里不大穩(wěn)定，引起了大家的注意。但是，獵戶座離我們有5萬光年之遠(yuǎn)。

Only half a dozen times in recorded history have supernovae been close enough to be visible tothe naked eye. One was a blast in 1054 that created the Crab Nebula. Another, in 1604, made astar bright enough to be seen during the day for over three weeks. The most recent was in1987, when a supernova flared in a zone of the cosmos known as the Large Magellanic Cloud,but that was only barely visible and only in the southern hemisphere—and it was acomfortably safe 169,000 light-years away.

在有記載的歷史上，只有五六次超新星是近到肉眼看得見的。一次是1054年的爆炸，形成了蟹狀星云。另一次是在1604年，創(chuàng)造了一顆亮得在3個(gè)多星期里連在白天都看得見的恒星。最近一次是在1987年，有一顆超新星在宇宙一個(gè)名叫大麥哲倫云的區(qū)域閃了一下，然而僅僅勉強(qiáng)看得見，而且僅僅在南半球看得見--它在16.9萬光年以外，對(duì)我們毫無危險(xiǎn)。