Why did they decide Pluto is no longer a planet?
It was misclassified. That is the short answer. Now, for the long answer. When Pluto was first discovered in 1930, it was hailed as the “ninth planet”. Even from the start, it was recognized as an “oddball” of the solar system. First of all, it had an unusual orbit. Most planets orbit the sun in an orderly fashion, sweeping out nearly-circular paths, and staying more-or-less in line with the sun’s rotation. But Pluto has more of a surfboard-shaped orbit, which takes it far “above” and “below” the other planets’ orbits, and occasionally even brings it inside of Neptune’s orbit. Pluto is also much smaller than the other eight planets, and has a different physical composition (being made of ice, rather than rock or gas like the others). In spite of these irregularities, Pluto was readily accepted as a planet by scientists, the public, and popular culture. Yet, in 1930, humans knew very little about the true nature of the outer solar system. As it turns out, Pluto was only the first discov
