Earth is a target in a cosmic shooting gallery, subject to random violent events that were unsuspected a few decades ago.

地球是“宇宙射击场”中的一个靶子，容易随机遭遇各种猛烈的撞击事件，这在数十年前从未受到过怀疑。

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One calls for launching microsatellites into low Earth orbit in constellations that would provide continuous target coverage.

其中之一是将小卫星发射到低地球轨道构成卫星星座，以便能提供对目标的持续覆盖。

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Given realistic propulsion options, and the requirement that the spacecraft can slow down to orbit its target, the target star cannot be more than 15 light-years from Earth.

根据实际的推进选择，以及航天器能够减速以环绕其目标公转的需要，目标恒星不能离地球超过15光年。

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If all goes well, NuSTAR's first target will be the black hole nearest Earth.

WSJ: NASA NuStar Telescope to Hunt for Black Holes

Dr Cordey said the company had worked with a number of space authorities on other methods of protecting the Earth from asteroids but this one would be able to target a wider range.

BBC: British plan to tackle asteroids

The inquiry comes after Wales failed to meet the 2010 biodiversity target set as part of the UK government's commitment to the Earth Summit.

BBC: Sustainability committee