Each member of the Lowell Observatory was allowed to vote on a short-list of three names . The names were Minerva ( which was already the name for an asteroid ) , Cronus , and Pluto . Each member of the Lowell Observatory was allowed to vote on a short-list of three : Minerva ( which was already the name for an asteroid ) , Cronus ( which had lost reputation through being proposed by the unpopular astronomer Thomas Jefferson Jackson See ) , and Pluto .