If it were to blow up~

以下在講一顆恆星爆炸
If it were to blow up before moving away from us it would wipe out life on Earth.
文章的中文翻譯是"如果它在遠離我們之前爆炸,那將會滅絶地球上的一切生物"

但這句話的假設語氣文法與我知道的結構都不符合
請高手協助說明這句話的文法是如何應用的,多謝!
3 個解答 3