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托福听力练习-科学美国人60秒:银河系的重量

2017-03-11 17:02:00来源：科学美国人60秒

点击查看>>科学美国人60秒音频：银河系的重量

　　科学美国人60秒中英文翻译：银河系的重量

　　科学美国人60秒英文文本

　　Weighing the Milky Way is no easy task. It's not like you can just step outside the galaxy and place it on a humongous scale.

　　Plus, most of the galaxy's heft is in invisible dark matter, which betrays its presence only through its gravitational pull. So astronomers have devised clever ways of inferring the mass of our galaxy by measuring how it pulls on smaller objects moving around it.

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　　A new estimate, based on its effect on the motion of a nearby dwarf galaxy, has the Milky Way a bit beefier than some past measurements that relied on the motions of massive stars. The study is in the Astrophysical Journal.

　　The researchers first used the Hubble Space Telescope to track the dwarf galaxy Leo I, which at 850,000 light-years away is one of the most distant of the satellite galaxies swarming around the Milky Way. Then they simulated galaxies able to host such an object. Turns out that anything less massive than one trillion suns is very unlikely. In fact, the researchers estimate that the Milky Way's dark matter has as much mass as 1.6 trillion suns. That's some pretty heavy-duty astrophysics.

　　中文翻译请点击下一页

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