英语听力：自然百科 穿越银河系的旅行 Through Milky Way—19
时间：2014-05-27 07:09:58
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（单词翻译）
One of the puzzles about our galaxy1 is that we know that it's had stars forming continuously for about the last ten billion years. But at the rate/ it's eating up its gas now, it's forming new stars, it should burn out that gas soon, should run out of fuel, and so there has to be some source/ for new fuel.
That source must be beyond the galaxy. And recently,
astronomers2 have made an
astounding3 discovery. Globular clusters are not the only groups of stars orbiting the Milk Way, there are also ultra-faint
dwarf4 galaxies5.
The reason why we haven’t known about these dwarf galaxies for very long, these so called ultra-faint dwarf galaxies, is that they contain just a few hundred stars, a thousand stars. So, you try to find a column of a thousand/ stars while looking through a mass of a billion stars, it is not easy. It's the needle-in-a-haystack problem. And it's only because we have the precise maps, it's precision of modern astronomy that's allowed us to discover these extremely interesting dwarf galaxies.
They may be
illusive6, but they can help to solve the mystery of what's fueling the galaxy.
So these dwarf galaxies are whizzing around our galaxy, they are orbiting around it. Now sometimes they get to close, and when they get too close, they get ripped apart, in fact they get eaten as some things by our galaxy.
This computer model shows dwarf galaxies as colored discs. Over time our galaxy at the center
devours7 many of them, pulled in by gravity, supplying more gas and dust from which / new stars / will eventually form.
So in much the same way that a large city might sort of cannibalize its neighbors, the
Milky8 Way is cannibalizing its dwarf galaxy population.
Globular clusters and dwarf galaxies give an insight just how old our galaxy is, and how it's survived for so long.
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