Transcript: When Pluto was discovered in 1930 it was hailed as the ninth planet, a great discovery of the twentieth century. Its discoverer Clyde Tombaugh was celebrated as the only living person to have discovered a planet. Now astronomers are not so sure whether Pluto is a planet or an interplanetary body for a number of reasons. Pluto is small, less than half the size of Mercury. Its orbit is the most elliptical in the solar system, crossing that of Neptune. There are other interplanetary bodies of similar size, although none quite as large as Pluto. Triton is similar in size, and it is a captured satellite. Pluto does have a moon, but so do interplanetary bodies. A few years ago the astronomers’ official governing body downgraded Pluto causing some consternation among the planetary science community and among the public.