Studying the Atmospheres of Pluto, Titan and Eris with Stellar Occultations

On rare occasions, a planet moves in front of a relatively bright star. During these events, called occultations, the starlight shines through the planet's atmosphere and provides a sensitive measure of its pressure, temperature and density profiles. In the case of Pluto, stellar occultations let us monitor the atmosphere's column abundance as Pluto moves away from the Sun, and subsequently lets us examine the thermal inertia of Pluto's subsurface. For Titan, the occultation lightcurves provide vertical maps of the haze distribution with 1-km resolution, useful for addressing the question of how hazes form on Titan and how they are transported through the atmosphere. Eris is a distant Pluto-sized object on an eccentric orbit. Eris may have a thin atmosphere at the present time and certainly has one when Eris is close to the Sun. Stellar occultations will let us look for thin atmospheres and constrain the temperatures and compositions of surface ices.