很难的一句英语：Upwards of a billion stars in our galaxy have burnt
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
后半句
and so can no longer produce the heat a star needs to oppose the inward force of gravity
是什么结构,哪个是主语,谓语动词,哪个是宾语,哪些是定状补
用了省略 或者倒装了吗