I cant find any info on how he became the star.
Realy, shouldnt that be here?
18.104.22.168 05:56, February 16, 2011 (UTC)
He was send to heaven for stealing a shiny stones from one the Alver to win marriage to Elrond and Elos's mother.
He went to Aman to make a plee for help. The law that the Valar had set forth meant that no mortals who set foot on Valinor were allowed to return, so Eärendil became an Elf and was set to guide the Silmaril that he bore through the heavens.