Hobbies And Interests
Mythological Names
Pluto was named for the Roman god of the underworld. The name was chosen by a young school girl in Oxford, England soon after the planet's discovery by Clyde Tombaugh and his team in 1930. "Pluto" seemed perfect for the mysterious, remote heavenly object. Mike Brown of Cal Tech, whose team discovered Sedna in 2003, chose the name of the Alaskan Inuit Indian goddess because of its extreme cold surface temperature.
Anything but Planets
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune are undisputed planets in our solar system. Since 2006, Pluto and Sedna, among other heavenly bodies, have been classified as "dwarf planets" by the International Astronomical Union. The astronomers who discovered Sedna prefer to call Pluto and Sedna "asteroids." Still others in the scientific community prefer to call them "planetoids." All parties seem to agree, however, that they belong in the same class of heavenly body.
Composition
Both Pluto and Sedna appear reddish in color in telescope photos taken from Earth and from space. Both dwarf planets are thought to be roughly composed of half rock and half ice. That combination is similar to the composition of most comets in our solar system. Sedna's orbit has even been compared to that of a comet, but astronomers stop short of labeling it one because it has gravity.
Irregular Orbits
Both Pluto and Sedna have irregular and long orbits around the sun. Pluto's 248 year-long orbital path is elliptical and very strange. There are times when Pluto is actually closer to the sun then Neptune, its next nearest planetary neighbor. Sedna's long orbit is even more elliptical. It orbits the sun much like comets do, but it is much farther out than most comets found in our solar system. In fact, Sedna's orbit around the sun takes 10,500 years to complete.