很难的一句英语：Upwards of a billion stars in our galaxy have burnt

题目

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

答案

这个句子,前后句主语是一样的,所以so后面其实省略了主语（这里据我推测应该是stars）.难度并不是很大.and并列的是两个主语后的部分,即burnt up和 can no longer.