萬物簡史 第28期:走進(jìn)太陽系(6)

　　So if Pluto really is a planet, it is certainly an oddone. It is very tiny: just one-quarter of 1 percent asmassive as Earth. If you set it down on top of theUnited States, it would cover not quite half the lowerforty-eight states.

　　因此，如果冥王星真是一顆行星，那肯定是一顆很怪的行星。它很小，只有地球的四百分之一大。假如你把它蓋在美國上面，它還蓋不住美國本土48州的一半面積。

　　This alone makes it extremely anomalous; itmeans that our planetary system consists of fourrocky inner planets, four gassy outer giants, and atiny, solitary iceball. Moreover, there is every reason to suppose that we may soon begin tofind other even larger icy spheres in the same portion of space.

　　光這一點(diǎn)就使它顯得極其反常，這說明，我們的行星系統(tǒng)是由4顆穩(wěn)固的內(nèi)行星、4顆氣態(tài)的外行星和1顆孤獨(dú)的小冰球組成的。

　　Then we will have problems. After Christy spotted Pluto's moon, astronomers began to regardthat section of the cosmos more attentively and as of early December 2002 had found over sixhundred additional Trans-Neptunian Objects, or Plutinos as they are alternatively called. One,dubbed Varuna, is nearly as big as Pluto's moon.

　　接著，問題又來了。克里斯蒂發(fā)現(xiàn)冥王星的衛(wèi)星以后，天文學(xué)家開始更加仔細(xì)地觀察宇宙的這一部分，截至2002年12月初止，又在天王星以外發(fā)現(xiàn)了600多個物體，其中一顆被命名為伐樓拿星，差不多和冥王星的衛(wèi)星一般大小。

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

　　天文學(xué)家現(xiàn)在認(rèn)為，也許存在幾十億個這類物體。困難在于，它們當(dāng)中有許多暗淡無光。一般來說，它們的反射度只有4%，大約相當(dāng)于一塊木炭的反射度--當(dāng)然，這些"木炭"是在60多億公里以外。