They are thought to travel to Earth from other galaxies and extragalactic sources.

他们被认为是从其他星系和星系外到地球。

That's because scientists don't know for sure if they've identified an extragalactic exoplanet.

这是因为们不确定他们是否发现了一颗银河系外行星。

The researchers say more data will be needed to confirm the observation as an actual " extragalactic exoplanet" .

研究人员说，还需要更多数据证实这是一颗真正" 星系外系外行星" 。