Albedo and atmospheric constraints of dwarf planet Makemake from a stellar occultation

Makemake is an icy dwarf planet with a spectrum similar to Eris and Pluto, and is currently at a distance to the Sun intermediate between the two. Although Makemake’s size (1,420±60km) and albedo are roughly known, there has been no constraint on its density and there were expectations that it could have a Pluto-like atmosphere. Here we report the results from a stellar occultation by Makemake on 2011 April 23. Our preferred solution that fits the occultation chords corresponds to a body with projected axes of 1,430±9km (1σ) and 1,502±45km, implying a V-band geometric albedo pV = 0.77±0.03. This albedo is larger than that of Pluto, but smaller than that of Eris. The disappearances and reappearances of the star were abrupt, showing that Makemake has no global Pluto-like atmosphere at an upper limit of 4–12nanobar (1σ) for the surface pressure, although a localized atmosphere is possible. A density of 1.7±0.3gcm−3 is inferred from the data.

(Nature 491, 566–569, 22 November 2012)

17/01/2012 - 13:30
José Luis Ortiz