The X-ray image shows an expanding shell of hot gas produced by the explosion.
这张X射线的照片展示了爆炸后产生的气体膨胀的外壳。
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Such stars eventually blow off the material of their outer layers, which creates an expanding shell of gas called a planetary nebula.
这样的恒星最终炸开了它们的外层物质，形成了向外扩展的气体盔甲，名为行星状星云。
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Infrared images from the Spitzer Space Telescope (yellow, red, and green) expose a surrounding shell of dust and gas that's being lit up as the material streams through a nearby star cluster.