地球历史上的这次重大灾难以物种的大量消亡为标志；当时，地球上多达一半的物种都灭绝了。

This break in Earth's history is marked by a mass extinction, when as many as half the species on the planet became extinct.

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作为银河系最密集的一部分，大量恒星周期性诞生消亡产生了这些尘埃。

Being such a crowded part of the Galaxy, there have been many cycles of starbirth to produce such dust.

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这也意味着大的恒星快速地释放大量的物质，在大规模的爆炸中燃烧自己，从而寿命短，消亡早。

That also means that massive stars live fast and die young, quickly shedding huge amounts of material and burning themselves out in what are thought to be spectacular explosions.

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