万物简史 第28期:走进太阳系(6)

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　　因此，如果冥王星真是一颗行星，那肯定是一颗很怪的行星。它很小，只有地球的四百分之一大。假如你把它盖在美国上面，它还盖不住美国本土48州的一半面积。

　　This alone makes it extremely anomalous²; it means that our planetary system consists of four rocky inner planets, four gassy outer giants, and a tiny, solitary³ iceball. Moreover, there is every reason to suppose that we may soon begin to find other even larger icy spheres in the same portion of space.

　　光这一点就使它显得极其反常，这说明，我们的行星系统是由4颗稳固的内行星、4颗气态的外行星和1颗孤独的小冰球组成的。

　　Then we will have problems. After Christy spotted⁴ Pluto's moon, astronomers⁵ began to regard that section of the cosmos⁶ more attentively⁷ and as of early December 2002 had found over six hundred additional Trans-Neptunian Objects, or Plutinos as they are alternatively called. One, dubbed⁸ Varuna, is nearly as big as Pluto's moon.

　　接着，问题又来了。克里斯蒂发现冥王星的卫星以后，天文学家开始更加仔细地观察宇宙的这一部分，截至2002年12月初止，又在天王星以外发现了600多个物体，其中一颗被命名为伐楼拿星，差不多和冥王星的卫星一般大小。

　　Astronomers now think there may be billions of these objects. The difficulty is that many of them are awfully⁹ dark. Typically they have an albedo, or reflectiveness, of just 4 percent, about the same as a lump of charcoal¹⁰—and of course these lumps of charcoal are about four billion miles away.

　　天文学家现在认为，也许存在几十亿个这类物体。困难在于，它们当中有许多暗淡无光。一般来说，它们的反射度只有4％，大约相当于一块木炭的反射度--当然，这些"木炭"是在60多亿公里以外。

 

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