Results from a stellar occultation by the dwarf planet Makemake

Pluto and Eris are icy dwarf planets with nearly identical accurately measured sizes, comparable densities, and similar surface compositions. Their different albedos and current distances from the Sun are likely reasons why Pluto possesses an atmosphere whereas Eris does not. Makemake, another icy dwarf planet with a similar spectrum to Eris and Pluto is currently at intermediate distance to the Sun between the two. Makemake’s size and albedo were poorly known, there was no constraint on its density and there were expectations that it could have a Pluto-like atmosphere. Here we will show results from a stellar occultation by Makemake that allowed us to determine its size and shape but also its geometric albedo (which turned out to be intermediate to that of Pluto and Eris). We will also show that Makemake does not have a global Pluto-like atmosphere at an upper limit of 4 to 12 nbar (1-sigma) for the surface pressure. We will discuss other implications.

17/01/2013 - 13:30
José Luis Ortiz