時(shí)差N小時(shí):灶神星

You can see the planet Jupiter on a clear night, but Jupiter ishumongous.

在晴朗的夜空下我們能夠看到木星，那是因?yàn)槟拘菈虼?

Mars and Mercury are smaller than that, and youcan see them, too.

盡管火星和水星比木星要小，但我們依然能看到。

Wait a minute, our moon is even smaller,and you can see that.

等等，月球更要小一些，我們還是能看到。

Could anything smaller than the moon be visible without a telescope?

那么，在不使用望遠(yuǎn)鏡的情況下，我們還能看到比月亮更小的天體嗎?

Actually, yes.

事實(shí)上，答案是肯定的。

Though it takes a lot of patience and excellent sky conditions, it is possible to see atiny object called Vesta.

只要我們足夠有耐心，天公也作美，我們還有機(jī)會(huì)看到一個(gè)小天體—它就是被命名為灶神星的小天體。

Although it had a molten interior and volcanoes, Vesta isn't a planet or amoon: it's an asteroid.

盡管它以溶化的金屬為核心且地表遍布火山，灶神星卻既不是行星也不是月球：它僅僅是一顆小行星。

Asteroids are straychunks of rocky or metallic materials that orbit thesun but were never drawn into any of the planets.

小行星是由巖石或是金屬塊構(gòu)成的小天體，他們繞太陽運(yùn)動(dòng)但絕不會(huì)卷入其他行星的運(yùn)行軌道中。

Vesta is quite far away.

灶神星距地球的距離很遠(yuǎn)。

Like many asteroids, it has an orbit out between the orbits of Mars and Jupiter.

像其它許多小行星一樣，它在火星與木星之間有自己的運(yùn)行軌道。

Astronomers first spotted it when looking for a new planet they thought should existbetween these two.

天文學(xué)家們首次發(fā)現(xiàn)它時(shí)是在尋找介于這兩大行星間的另一個(gè)行星。

As I said, Vesta is quite small-about three hundred and twenty-five miles across.

正如我所說，灶神星是很小的—它的直徑也就只有325英里而已。

So if it's small and far away, how come we can see it from here?

那問題就是，它又小，距離我們又遠(yuǎn)，我們怎么能從地球上靠肉眼就看到它呢?

Vesta's surface has a coating of pyroxine and olivine,two minerals that are actually also spewed up by volcanoes here on earth.

在灶神星的表面覆蓋了厚厚的一層玄武巖和橄欖石，這兩種礦物質(zhì)都是由此處的火上噴發(fā)而出的。

They give it a whitishexterior that reflects well,

這兩種礦物質(zhì)使得灶神星的表面呈白色，且發(fā)光的效果相當(dāng)好。

making it just possible to see Vesta with your eyes, even when the onlytwo larger asteroids, Ceres and Pallas, are completely invisible.

如此一來，我們便僅憑肉眼就可以看到灶神星了。甚至在比它還大的另外兩個(gè)小行星—谷神星和智神星都無法看到的情況下，我們還是能看到它。