But after the X-ray pulse passes through, the cloud fades to its normal brightness.

但当X射线脉冲通过后星云就暗淡下来回到通常的亮度。

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They report in their paper that this is likely due to a thermal pulse where a wave of high-pressure gas mixes layers of elements like carbon and oxygen and spews them out into the surrounding cloud.

在报告中，他们解释说这估计是因为热脉冲膨胀把的C、O等喷发到周围的气体云，就像高压气体把多层基础冲乱一样。

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Once the "messenger" group had merged with the second cloud, a second laser was shone through the condensate to revive the original pulse of light.

BBC: NEWS | Science/Nature | Cool clouds turn light to matter