From the Minor Planet Mailing list (via the IAU Circulars):
(134340) PLUTO, (136199) ERIS, AND (136199) ERIS I (DYSNOMIA)
Following the Aug. 24 resolution by the IAU to the effect that
the solar system contains eight "planets" (Mercury-Neptune), with
(1) Ceres, Pluto (cf. IAUC 255), and 2003 UB_313 (cf. IAUC 8577) to
be considered representative "dwarf planets", the Minor Planet
Center included Pluto and 2003 UB_313 (along with two other new
potential dwarf-planet candidates) in the standard catalogue of
numbered objects with well-determined orbits as (134340) and
(136199), respectively (see MPC 57525). Following near-unanimous
acceptance by both the Committee on Small-Body Nomenclature and the
Working Group on Planetary-System Nomenclature (in consultation
with the discovery team), the IAU Executive Committee has now
approved the names Eris for (136199) and Dysnomia for its satellite
(136199) Eris I [formerly S/2005 (2003 UB_313) 1; cf. IAUC 8610].
special PDF circular
Eris is the goddess of strike, discord, and rivalry, and Dysnomia is the goddess of lawlessness.
My last post about the MPC designations for Pluto & the other large KBOs
2003 UB 313, Pluto, and other related Kuiper Belt posts:
An animation of Pluto
Direct measurements of 2003 UB 313
More science on 2003 UB 313
The The definition of a planet: IAU conference and the issue of 2003 UB313
Pluto's new moons named: Nix and Hydra
New Horizons--aka the Pluto and Kuiper Belt mission
2003 EL61: bulgy or salt and pepper?
Huge new Kuiper Belt Object / Transneptunian Object?