Eris - The Largest Dwarf Planet
Created | Updated May 12, 2010
The Solar System
| Mercury
| Venus
| Earth
| Mars
| Ceres
| Jupiter
|
Saturn
| Chiron - a Celestial Entity
| Uranus
| Neptune
| Pluto
| The Kuiper Belt and The Oort Cloud
| Semi-planet Quaoar | Eris
| Sedna
Largest of the dwarf planets, Eris has been a source of consternation from the day it was first recognised as being a member of the The Solar System.
Discovered by the team of Brown,Trujillo, and Rabinowitz on 21 October, 2003, It has been named Eris after the goddess of discord after throwing large segments of the astronomical community into conflict as to whether it should be deemed a planet. The final decision was that this is not a planet.
The Facts
- Diameter: 2,400km
- Satellites: 1
- Mass: 0.0166x1024kg
- Mean Density: 2.3g/cm3
- Length of Day: 26hours1
- Period of Revolution about Sun: 556 years
- Acceleration due to Gravity on surface: 0.61 m/s2
- Mean Orbital Velocity: 3.436km/s
- Mean Distance from the Sun : 67.67 AU2
- Eccentricity: 0.4118
- Perihelion: 37.78 AU
- Aphelion: 97.56 AU
- Magnitude: 18.8
The orbit of Eris is very eccentric: it is inclined at an angle of 44.19° degrees to the plane on which Jupiter orbits. This
compares to 17° for Pluto and 11.9° for Sedna. This extreme angle places it south of the zodiac in the constellation Cetus (The Whale). The dwarf planet
Eris and its companion are currently near their furthest point from the sun. At this distance the surface temperature is 27°K (-246°C). At this temperature the methane which would have comprised its atmosphere is frozen.
By studying the motion of its moon, Dysnomia, scientists were able to deduce the mass of the Dwarf Planet but as of 2007 they still had not figured out anything about the length of a day on Eris. Use of the Swift Telescope in 2008 resulted in a likely value for one day.
Mythology
Eris is named after the Greek goddess of strife and discord.
One account has her tossing an apple labeled 'to the most beautiful' into the midst of three goddesses. This caused a dispute about who the apple referred to. Rather than summon her to explain Zeus instead commissioned Paris to choose who the most beautiful was. The three goddesses attempted to bribe Paris. He chose Aphrodite who had offered him Helen of Troy, initiating the Trojan War - much to the delight of Eris.
The Controversy
This object almost became a planet. The decision to make Eris and Pluto dwarf planets was decided on the basis of pragmatism rather than science. Had Eris been discovered forty years earlier it would have been a planet, but by the turn of the century a multitude of objects had been found in the Kuiper Belt and they couldn't all be planets just because they rotate around the sun, so where do you draw the line? In August 2006 astronomers meeting in Prague struggled with this problem, and finding one that was actually larger than Pluto they had to ask 'Were we wrong making Pluto a planet, and just what is a planet, anyway?' Some wanted to keep Pluto as a planet, and make Eris the next planet. The group that had the most votes, however, wanted to have no more additions to the list and hold the number at eight. So then what do you call something that is larger than Pluto and rotates around the Sun? The answer they came up with is a dwarf planet.
Dysnomia
The moon of Eris was discovered in September 2005. When the name Eris was submitted it was decided to use the name of one of her daughters to name this satellite.
Dysnomia translates to Lawless One. It rotates around Eris once in 15.774 days and has a diameter less than 150km.
The h2g2 Tour of the Solar System
Take the h2g2 Shuttle for your whistle-stop tour of the Solar System.
In The Neighbourhood- Explore locally
Next Stop (Inward Journey):
Next Stop (Outward Journey)
