Pluto- what is it?
Pluto is the ninth planet in our solar system, and was discovered in 1930. Pluto is different from the other planets, because it's not classified as a gas giant planet, or a terrestrial planet. The reason pluto is not considered a either of these is, because it has too small of a density to be considered a terrestrial planet, and is made up of rock, and ice, and no gas. Pluto's orbit is so eccentric that its aphelion is 50 AU from the sun, and its perihelion is 30 AU from the sun. When Pluto is at its perihelion it's closer to the sun than Neptune. The axis of Pluto is turned over so far that the north pole points south of its orbital plane.
Pluto has one satellite called Charon, which orbits in Plutos equatorial plane. Charon, and Pluto have very similar masses, which has the most similar satellite pair in the solar system. They are in synchronous rotation with each other, this means that Pluto, and Charon keep the same side facing each other. The properties of Pluto are very similar to those of moons in gas giant planets. It's believed that Pluto was once a moon of Neptune's, which would explain why Pluto is highly eccentric.
Picture from: http://csep10.phys.utk.edu/astr161/lect/pluto/pluto.html
Pluto has one satellite called Charon, which orbits in Plutos equatorial plane. Charon, and Pluto have very similar masses, which has the most similar satellite pair in the solar system. They are in synchronous rotation with each other, this means that Pluto, and Charon keep the same side facing each other. The properties of Pluto are very similar to those of moons in gas giant planets. It's believed that Pluto was once a moon of Neptune's, which would explain why Pluto is highly eccentric.
Picture from: http://csep10.phys.utk.edu/astr161/lect/pluto/pluto.html