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

们被认为星系和星系外的来源来到地球的。

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

这因为科学家们不确定们现了一颗银河系外的行星。

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

研究人员说，还需要更多的数据来证实这一颗真正的" 星系外系外行星" 。