“a nine day's wonder”可以理解为“九天的奇迹”，其实就是我们中文说的“昙花一现”，可以用来形容一时引起轰动但是很快就被遗忘的事物或人。

【例句】
Last year the art critics praised Jonas as if he were a maser, but he turned out to be a nine day's wonder.
去年艺术评论家们还赞颂乔纳斯为大师呢，但后来证明它只是一个昙花一现的人物。

As a pop star she was a nine days'wonder: she only made one successful record.
她是个昙花一现的歌星,只录制过一张受欢迎的唱片。