Faraway Eris is Pluto's Twin

European astronomers have accurately measured the diameter of the dwarf planet Eris for the first time. Using the faint light of a distant star as Eris passed in front of it, astronomers were able to ascertain the dwarf planets size.

This event was seen at the end of 2010 by telescopes in Chile, including the Belgian TRAPPIST telescope at ESO’s La Silla Observatory. The observations show that Eris is an almost perfect twin of Pluto in size. Eris appears to have a very reflective surface, suggesting that it is uniformly covered in a thin layer of ice, probably a frozen atmosphere. The results will be published in the 27 October 2011 issue of the journal Nature.

ESO - eso1142 - Faraway Eris is Pluto's Twin