![]() Low-resolution image of Eris and Dysnomia as imaged by the Hubble Space Telescope, August 2006 | |
Discovery | |
---|---|
Discovered by | Brown et al.[a][1] |
Discovery date | 10 September 2005[1] |
Designations | |
Designation | Eris I |
Pronunciation | /dɪsˈnoʊmiə/, /daɪˈsnoʊmiə/[b] |
Named after | Δυσνομία Dysnomia |
S/2005 (2003 UB313) 1 Dy /ˈdaɪ/ (nickname) Gabrielle (nickname) | |
Adjectives | Dysnomian |
Orbital characteristics[2]: 5 | |
Epoch 31 August 2006 (JD 2453979.0) | |
37273±64 km | |
Eccentricity | 0.0062±0.0010 |
15.785899±0.000050 d | |
Average orbital speed | 0.172 km/s[c] |
Inclination | ≈ 0° (to Eris's equator; assumed) 78.29°±0.65° (to Eris's orbit) 45.49°±0.15° (to celestial equator) 61.59°±0.16° (to ecliptic)[d] |
126.17°±0.26° | |
180.83°[e] | |
Satellite of | Eris |
Physical characteristics | |
615+60 −50 km[3]: 7 | |
Mass | (8.2±5.7)×1019 kg[3]: 6 |
Mean density | 0.7±0.5 g/cm3[3]: 7 |
synchronous[4] | |
≈ 0° to orbit (assumed) | |
Albedo | 0.05±0.01[3]: 7 |
25.4[f] | |
5.6[f] | |
Dysnomia (formally (136199) Eris I Dysnomia) is the only known moon of the dwarf planet Eris and is the second-largest known moon of a dwarf planet, after Pluto I Charon. It was discovered in September 2005 by Mike Brown and the Laser Guide Star Adaptive Optics (LGSAO) team at the W. M. Keck Observatory. It carried the provisional designation of S/2005 (2003 UB313) 1 until it was officially named Dysnomia (from the Ancient Greek word Δυσνομία meaning anarchy/lawlessness) in September 2006, after the daughter of the Greek goddess Eris.[6]
With an estimated diameter of 615+60
−50 km, Dysnomia spans 24% to 29% of Eris's diameter. It is significantly less massive than Eris, with a density consistent with it being mainly composed of ice.[3]: 8 In stark contrast to Eris's highly-reflective icy surface, Dysnomia has a very dark surface that reflects 5% of incoming visible light,[3] resembling typical trans-Neptunian objects around Dysnomia's size.[7] These physical properties indicate Dysnomia likely formed from a large impact on Eris, in a similar manner to other binary dwarf planet systems like Pluto and Orcus, and the Earth–Moon system.
Cite error: There are <ref group=lower-alpha>
tags or {{efn}}
templates on this page, but the references will not show without a {{reflist|group=lower-alpha}}
template or {{notelist}}
template (see the help page).
Brown2006-discovery
was invoked but never defined (see the help page).Holler2021
was invoked but never defined (see the help page).Brown2023
was invoked but never defined (see the help page).Szakats2022
was invoked but never defined (see the help page).Grundy-Eris
was invoked but never defined (see the help page).IAUC 8747
was invoked but never defined (see the help page).Brown2018
was invoked but never defined (see the help page).