Upwards of a billion stars in our galaxy have burnt up their internal energy sources, and so can no longer produce the heat a star needs to oppose the inward force of gravity.

在我们的星系中，超过10亿颗恒星已经耗尽了它们的内部能量来源，因此无法再产生恒星所需的热量来对抗向内的引力。