Pluto Pluto was discovered in 1930, and its satellite, Charon, was discovered in 1978. Pluto is a tiny, low-density planet made up of 97 percent nitro
{"Image DocumentName": "Pluto", "Image ImageDescription": "Pluto was discovered in 1930, and its satellite, Charon, was discovered in Pluto is a tiny, low-density planet made up of 97 percent nitrogen and small amounts of frozen carbon monoxide and methane. Consistent variations in brightness can be observed on Pluto, indicating that its surface is irregular. Astronomers have used these variations to help determine the planet s rotational period: 6 days, 9 hours, and 17 minutes, in Earth time. Pluto s orbit is much more elliptic than those of the other planets and is tilted 17 degrees from the ecliptic plane. When it is at perihelion, Pluto is nearer the sun than is Neptune. Pluto s eccentric orbit and its physical similarities to icy satellites originally led some astronomers to believe that Pluto did not have the same origin as the other planets. One theory suggested that Pluto and Charon may once have been satellites of Neptune but were pulled away from Neptune s gravitational field. Most scientists, however, no longer believe this model is physically plausible.", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}