"tb42"> But why do stars shine in the first place? A star is made when a huge cloud of mostly hydrogen gas collapses. As the cloud gets denser, it also gets hotter. Finally, the center of the cloud gets so hot that it begins to produce its own energy through nuclear reactions. The temperature in the middle of our sun is about fifteen million degrees. That s hard to imagine! 不过星星为何会发光呢？当一个主要由氢气组成的星气团崩解时，一颗星星就形成了。当云变得更绸密时，温度也会跟着升高，最后，星云的中心温度不断升高，然后就形成核反应所产生的能量。太阳中心点的温度大约是一千五百万度，真是令人难以想象。 编辑推荐：名师指导公共英语阅读考试技巧 公共英语pets三级全真模拟试卷 公共英语pets二级语法讲解汇总