Dysnomia (moon)

Dysnomia (formally (136199) Eris I Dysnomia) is the only known <a href="/facts/Natural_satellite/AE4KQKbq">moon</a> of the <a href="/facts/Dwarf_planet/IkQoCdwD">dwarf planet</a> <a href="/facts/Eris_(dwarf_planet)/vuaR65F7">Eris</a> and is the second-largest known moon of a dwarf planet, after <a href="/facts/Charon_(moon)/elazjsMp">Pluto I Charon</a>. It was discovered in September 2005 by <a href="/facts/Michael_E._Brown/Y5Jn22Tl">Mike Brown</a> and the Laser Guide Star <a href="/facts/Adaptive_Optics/D1vWeHK0">Adaptive Optics</a> (LGSAO) team at the <a href="/facts/W._M._Keck_Observatory/4yhJmNde">W. M. Keck Observatory</a>. It carried the <a href="/facts/Provisional_designation/1XVyJynE">provisional designation</a> 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 <a href="/facts/Dysnomia_(deity)/0KsLkE1v">daughter</a> of the Greek goddess <a href="/facts/Eris_(mythology)/E3xrEVqq">Eris</a>.
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.: 8  In stark contrast to Eris's highly-reflective icy surface, Dysnomia has a very dark surface that reflects 5% of incoming visible light, resembling typical <a href="/facts/Trans-Neptunian_object/oF5vsbz9">trans-Neptunian objects</a> around Dysnomia's size. 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 <a href="/facts/Orcus_(dwarf_planet)/PbDdmqbd">Orcus</a>, and the Earth–Moon system.

Dysnomia (moon) open-in-new

Dysnomia (moon)