Is there a limit to how large a planet can be to support life? i always was fascinated at how large the sun vy canis majoris was, though it's not as hot as smaller suns, theoretically it could still support life if planets were in the right proximity to it. it would be fascinating if there were planets as large or larger, not just gaseous planets, than the largest known sun. theoretically, if there was a planet as large, how long would it take to discover and map it all? earth is a pretty small planet with much of it already explored except for the ocean bottoms.