The idea of rogue planets wandering the galaxy is not as far-fetched as it may sound. Gravitational tugs-of-war with other planets or passing stars can boot a planet out of its solar system.

流浪行星在星系中游走这个概念并没有它听起来那么难以捉摸，与其他星球或流星的引力之战很有可能使该星球脱离太阳系。

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It will also map out in 3D the distribution of galaxy clusters, measuring what are known as baryon acoustic oscillations - literally relics of the sound echoes of the Big Bang.

BBC: Dark energy camera snaps first images ahead of survey