The voice is not quite perfect on this sentence, as of August 7th, 2017, so I've taken the liberty of re-recording it.
As many others have noted in this thread and elsewhere, stressing PLAnet means "the plane". The stress should be on the second syllable.
Please find a correct recording on http://duolingo.vydea.io/87628c248b0c4640b9aa51e2329999db.mp3
For more info on re-recordings, please check the info thread: https://www.duolingo.com/comment/23723515
Thanks for listening. Ha en bra dag! :)