Conventional theory suggests that it must have formed like a star, from a collapsing cloud of interstellar gas.

传统的理论认为它一定像一颗恒星那样是由一团星际气体形成的压缩星云组成的。

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Within the cloud, some parts are sufficiently dense to start collapsing under their own gravity.

在星云里面，某些部分足够致密而在自身重力影响下开始塌缩。

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Collapsing interstellar cloud reverses its gravitational infall and expands outward into the relatively quiescent interstellar environment.

坍缩的星际云克服向内的引力而向外膨胀到较宁静的星际环境中去。

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