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

他们被认为从其他星系和星系外来源来到。

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

因为科学家们不确定他们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，还需要更多数据来证实一颗真正" 星系外系外行星" 。