Dysnomia (moon)

  • M. E. Brown
  • C. A. Trujillo
  • D. L. Rabinowitz

Dysnomia, too ( 136199 ) Eris I, is the only known satellite of the most massive known dwarf planet Plutoiden and SDO asteroid Eris. Estimates of the diameter vary 100-490 kilometers.

Discovery and designation

Dysnomia was by Mike Brown ( Caltech ), Chadwick A. Trujillo (Gemini Observatory ) and David Rabinowitz Lincoln ( Yale University) on the 10-meter Keck II telescope on Mauna Kea in Hawaii with the laser guide star adaptive optics system discovered on 10 September 2005. Dysnomia was 0.53 ± 0.01 arcsec distance from Eris found a difference between the apparent magnitude of 4.43 ± 0.05. The name was provisionally Gabrielle suggested by the discovery team, the name of the Sidekick supporting role in the U.S. television series Xena. The discovery was announced on 4 October 2005; the moon was given the provisional designation S/2005 (2003 UB313 ) 1

On 13 September 2006, the moon was by the International Astronomical Union ( IAU) officially named ( " the Missgesetzlichkeit " Greek for ) by Dysnomia, in Greek mythology, the daughter of Eris and the Daimona of lawlessness.

The name was suggested for several reasons by Michael E. Brown. First, the tradition is taken into account to select the name of associated gods to the name of the primary object, secondly, the reference to the lawlessness (English lawlessness ) is a reference to the actress Lucy Lawless the figure of Xena the TV series of the same name, the loose plays in Greek mythology. In addition, Brown argues that the first two letters of the name are a reference to the name of his wife Diane, whose nickname " Di" is why he pronounce the moon also " Daisnomia ". He makes reference to Pluto, whose first two letters refer to Percival Lowell's initials, the Clyde Tombaughs search for the Planet X inspired and supported, and especially on Charon, indicate the first four letters of the woman whose discoverer James W. Christy Charlene.

Eris and Dysnomia addition, represent aspects of chaos and thus reflect the effects that had caused their discovery, namely the subsequent controversy on the definition of a planet, and in particular the debate over the status of Pluto and Ceres.

Web properties

Dysnomia Eris orbits a nearly circular orbit at 37,430 km average distance to the center (approx. 31 Erisradien ). The orbital eccentricity is a maximum of 0.013, the track is 61.3 ° or 142 ° inclined to the ecliptic.

Dysnomia Eris orbits in 15 days, 18 hours and 31.7 minutes, resulting in a Eris - year corresponds to approximately 12909.1 rounds (about 557.40 Earth years ).

Physical Properties

Since about Dysnomia has the 1/500 part of the luminosity of Eris, the diameter should be about 100 kilometers. If the albedo of Dysnomia is substantially less than that of Eris, the diameter may even be up to 250 kilometers. Other claims to the diameter may even be 350-490 km. The moon is probably too small to have been pressed by its own gravity in a spherical shape.

It is believed that Dysnomia inside largely of water ice and similar so probably the two moons of the dwarf planet Haumea.

The discovery team assumes that Dysnomia is caused by an impact of a large body of Eris, analogous to the theory of the origin of Earth's moon.


Since the discovery in 2005 Dysnomia was observed by ground-based telescopes and the Hubble Space Telescope, while its orbital elements could be determined. Since the albedo of the moon is still unknown, the information on the diameter of the moon are still very vague.

The discovery of Dysnomia conclusions on the mass of Eris could be drawn by its speed. Significantly, the discovery was primarily due to the fact that three of the four known dwarf planets of the outer solar system moons have, which suggests that these are frequent and in the Kuiper Belt and beyond frequently than in the main belt ( about 10%) are found.