Nature http://dx.doi.org/10.1038/nature11597 (2012)
The icy dwarf planet Makemake lies between dwarf planets Pluto and Eris. Measurements made when Makemake passed in front of a star suggest that, unlike Pluto, it lacks an appreciable atmosphere.
Jose Ortiz of the Instituto de Astrofísica de Andalucía, Spain, and a multinational group of colleagues recorded the passage of Makemake between a faint star and the Earth using seven telescopes from five sites. Timing the disappearance and reappearance of the star's light, they estimated the geometry of Makemake: slightly elliptical, with axes of about 1,430 and 1,500 kilometres. The researchers ruled out the existence of a global atmosphere such as that found on Pluto, which had previously been expected based on the size and surface reflectance of Makemake.
However, localized patches of atmosphere, possibly consisting of nitrogen or methane, are consistent with the data. The effects of such patches could help to explain earlier observations that require the presence of two different types of terrain on the dwarf planet's surface.