English-Chinese/Stars are hot because nuclear reactions happen inside them

The star is very hot because of a nuclear reaction inside. These reactions are called nuclear fusion. Nuclear fusion produces light and heat and produces increasingly large chemical elements.

恒星很热，因为内部发生核反应。 这些反应称为核聚变。 核聚变产生光和热，并产生越来越大的化学元素。