Dysnomia (moon)
Dysnomia, to the left, and Eris, center
(Hubble Space Telescope) |
|
| Discovery | |
|---|---|
| Discovered by | Michael E. Brown, M. A. van Dam, A. H. Bouchez, D. Le Mignant, R. D. Campbell, J. C. Y. Chin, A. Conrad, S. K. Hartman, E. M. Johansson, R. E. Lafon, D. L. Rabinowitz, P. J. Stomski Jr., D. M. Summers, C. A. Trujillo, and P. L. Wizinowich |
| Discovery date | September 10, 2005 |
| Designations | |
| MPC designation | (136199) Eris I Dysnomia |
| Pronunciation | /dɪsˈnoʊmiə/ or /daɪsˈnoʊmiə/ |
| S/2005 (2003 UB313) 1 | |
| Adjectives | Dysnomian |
| Orbital characteristics | |
| 37350±140 km | |
| Eccentricity | < 0.013 |
| 15.774±0.002 d | |
|
Average orbital speed
|
0.172 km/s |
| Inclination | 142°±3° |
| Satellite of | Eris |
| Physical characteristics | |
|
Equatorial radius
|
342±25 km (albedo five times lower than Eris's) |
| ~23.1 | |
| ~3.2 | |
Dysnomia (Greek: Δυσνομία)—officially (136199) Eris I Dysnomia—is the only known moon of the dwarf planet Eris (the most massive known dwarf planet in the Solar System). It was discovered in 2005 by Mike Brown and the laser guide star adaptive optics team at the W. M. Keck Observatory, and carried the provisional designation of S/2005 (2003 UB313) 1 until officially named Dysnomia (from the Ancient Greek word Δυσνομία meaning anarchy/lawlessness) after the daughter of the Greek goddess Eris.
During 2005, the adaptive optics team at the Keck telescopes in Hawaii carried out observations of the four brightest Kuiper belt objects (Pluto, Makemake, Haumea, and Eris), using the newly commissioned laser guide star adaptive optics system. Observations taken on 10 September revealed a moon in orbit around Eris, provisionally designated S/2005 (2003 UB313) 1. In keeping with the Xena nickname that was already in use for Eris, the moon was nicknamed "Gabrielle" by its discoverers, after Xena's sidekick.
Dysnomia was found 4.43 magnitudes fainter than Eris, and its diameter is estimated to be between 350 and 490 km, though Mike Brown claims that it is 500 times fainter and between 100 and 250 km in diameter. It is 60 times fainter than Eris in the K band and 480 times fainter in the V band, which means a very different, and quite redder, spectrum, indicating a significantly darker surface. Assuming its albedo is five times lower than Eris's, its diameter would be 685±50 km, meaning that Dysnomia is itself likely a rather large Trans-Neptunian object. Of the Solar System's dwarf planet and minor planet moons, only Charon is definitely larger than Dysnomia.
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