His first great discovery was made when he recognized a Cepheid variable star.It was in the outer area of the great nebula called Andromeda.是什么意思_His first great discovery was made when he recognized a Cepheid variable star.It was in the outer area of the great nebula called Andromeda.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句