Solar System -
Trans-Neptunian Objects
While no longer classified as a planet, Pluto remains the ninth largest, and tenth heaviest, object that orbits the sun directly. It is 2,372 km (1,483 miles) across. Ccompared, for example, to the Moon, which is 3,474 km (2,159miles) in diameter, it is relatively small. In fact, the SDO Eris is more than 25% heavier, though a few kilometers less in diameter at 2,326 km (1,454 miles) across. Pluto has five moons: Charon , Styx , Nix, Kerberos, and Hydra in order outwards from Pluto.
Pluto orbits the sun about every 248 Earth years. While the other planets orbit more or less in the plane of the ecliptic, Pluo's orbit is inclined over 17°. Its orbit is also rather an eccentric elipse taking it closer to the Sun than Neptune during part of its orbit for a period of about 20 Earth years. Pluto's orbit is in a 2:3 resonance with Neptune's meaning that for every three orbits Neptune makes around the Sun, Pluto makes just two, repeating every 496 years (approximately).
Pluto orbits the sun about every 248 Earth years. While the other planets orbit more or less in the plane of the ecliptic, Pluo's orbit is inclined over 17°. Its orbit is also rather an eccentric elipse taking it closer to the Sun than Neptune during part of its orbit for a period of about 20 Earth years. Pluto's orbit is in a 2:3 resonance with Neptune's meaning that for every three orbits Neptune makes around the Sun, Pluto makes just two, repeating every 496 years (approximately).
Pluto System
| Name | Diameter/Size (km) | Diameter/Size (Miles) | Orbits Pluto every (Days) | Discovered |
| Charon | 1,212 | 758 | 6.39 | 1978 |
| Styx | 16 x 9 x 8 | 10 x 5 x 5 | 20.16 | 2012 |
| Nix | 50 x 35 x 33 | 31 x 22 x 21 | 24.85 | 2005 |
| Kerberos | 19 x 10 x 9 | 12 x 6 x 6 | 32.17 | 2011 |
| Hydra | 65 x 45 x 25 | 41 x 28 x 16 | 38.2 | 2005 |