Some Astronomers Say "Long Live Planet Pluto - Latest …
Two people, John Couch Adams and Urbain Jean Joseph Le Verrier, satdown with pen and paper and a long set of measurements of the position ofUranus, and did the math to figure out where the unseen planet ought to bein the sky. Neither one had their own telescope, so they couldn't then golook for the object themselves. Adams then sent his answer off to GeorgeAiry, then the leading astronomer in Britain. Le Verrier sent his answeroff to Paris Observatory, and then to Berlin Observatory.
Why is Pluto no longer a planet? - BBC News
The "planet" defenders point out that we've called Pluto a planetsince it was found in 1930. Everybody is used to learning that thereare nine planets when they're in grade school, and we shouldn't justrewrite all the textbooks for no good reason. Also, it's a lotbigger than anything we call an asteroid. (Pluto is something like2400 kilometers across, 2/3 as big as the Moon. The largestasteroid, Ceres, is about 900 km.)
Posted - March 23, 2017
Is Pluto a planet or not? Pluto is a rocky celestial object and was the smallest of the nine planets when it still had the status. This definition differs from the three-element IAU definition in that it makes no reference to the celestial body's surroundings.