Eris is the dwarf planet with the most known mass in our solar system. He is one of the Plutoids, a subclass of dwarf planets that orbit the Sun beyond the orbit of Neptune.
After its discovery on 29 July 2005, the NASA and many media called this object of the Kuiper Belt with a similar diameter as Pluto initially as “tenth planet”. However the International Astronomical Union (IAU) published on 24 August 2006 a new planet definition – due to this new definition, Eris, just like Pluto, had to be classified as a dwarf planet. The object got accordingly to this a minor planet number 136199 in September 2006.
One solar circulation, a so called “year” on Eris, corresponds about 560 Earth years. The orbit is not unusual for an object of the Kuiper Belt, highly eccentric (numerical eccentricity 0.44). So the perihelion of its orbit is only 38 AU. It may temporarily be closer to the sun than Pluto, its aphelion is 49 AU. Currently, Eris is near the aphelion of its orbit, about 98 AU from the sun. This corresponds a distance of about 13.5 light hours.
Eris is large enough to hold a very thin atmosphere of nitrogen, methane and carbon monoxide like Pluto. This would periodically decrease with increasing distance from the Sun, and so decrease like the temperature on the surface. When the temperature rises again it would form an atmosphere again. Since Eris is currently staying very close to its aphelion, currently there is no atmosphere.
The surface temperature of Eris is estimated at 30 K (about -242 °C). It is therefore once again significantly lower than that of Pluto. This is primarily due to the greater distance from the sun.
Eris has a moon named Dysnomia, which was discovered on 10 September 2005 by the same team as Eris. Dysnomia required for one orbit around the dwarf planet nearly 16 days its distance to Eris is about 37,000 km.
| Discovery date | 2005 (M. E. Brown, C. A. Trujillo, D. L. Rabinowitz) |
| Semi-major axis | 10 126 130 222 km = 10.126 x 109 km (67.689 AU) Comparison: 67.689 x Earth |
| Perihelion | 5 684 719 820 km = 5.684 x 109 km (37.765 AU) Comparison: 37.765 x Earth |
| Aphelion | 14 602 547 286 km = 14.602 x 109 km (97.612 AU) Comparison: 97.612 x Earth |
| Diameter | 2326 km = 2.32 x 103 km Comparison: 0.1823 x Earth |
| Mass | 16 600 000 000 000 000 000 000 kg = 1.66 ±0,02 × 1022 kg Comparison: 0.00277 x Earth |
| Density | 2.3 g/cm3 Comparison: 0.4170 x Earth |
| Orbital period (Length of a year) |
560 Earth years 204 534 Earth days |
| Eccentricity | 0.44 Comparison: 26.3311 x Earth |
| Inclination | 44° |
| Minimum/Maximum surface temperature |
-242 °C = 30 K Comparison: The temperature of the Earth is ~ 185/331 K |
| Composition of the atmosphere |
unknown Comparison: The atmosphere of the Earth is mainly composed of N2 and O2. |
Moons:
Eris has one known moon named Dysnomia.