The Mass, Density, and Figure of the Kuiper Belt Dwarf Planet Makemake

The recent discovery and subsequent orbital characterization of Makemake's satellite have provided a means to measure the mass of the dwarf planet for the first time. As Makemake is a fast rotator, it is expected to have a non-spherical equilibrium figure. If the orbital pole of the satellite is aligned with the spin pole of Makemake, then the spin pole is nearly orthogonal to the occultation chords presented in Ortiz et al. (2012). It is difficult to constrain the equatorial radius of a spheroid aligned in such a way; the resulting preferred volume and its uncertainty are larger than previous estimates. The preferred figure has a ratio of equatorial to polar diameters of 1.13. Combining this new figure estimate and the mass measurement of 3.1x10²¹ kg, we derive a relatively low density for Makemake of 1.7 g/cc; adopting the Brown (2013) volume estimate results in a higher density of 2.1 g/cc. In this presentation, we will describe the existing and upcoming Hubble Space Telescope observations of the system that enable these mass and orbit plane measurements, derivation of the mass, figure, and density of Makemake, and the implications for the internal structure of Makemake. We will also describe possible upcoming opportunities to observe mutual events between Makemake and its satellite.