The Seven Dwarves

Thursday, 01 August 2013 1 p.m. — 2 p.m. MST

AURA Lecture Hall

NOIRLab South Colloquia
WESLEY FRASER (National Research Council Canada and Gemini South Visiting Astronomer)

The Kuiper Belt is a population of icy planetesimals which are left over from the planet formation process. It is now well accepted that Kuiper Belt Objects (KBOs) originated from a region closer to the Sun compared to their current locales. This presents one of the most attractive reasons for studying the Kuiper Belt: these objects provide a probe of a region of the primordial disk which is not afforded by any other planetesimal population. The compositions of KBOs therefore, hold the key to understanding the composition of the primordial disk. The observed surface compositions of large KBOs - the dwarf planets - are, in the most general sense, moderately well understood. That is, the existence of a volatile ice on one object, and the lack of that same ice on a similar object, can be simply explained by Jeans Escape. What remains unexplained (and unmeasured) however, is the specific fractional abundances of ices on KBOs, fractions that can be measured through study of their atmospheres.

To date, only one atmosphere around a KBO is known, that of Pluto. This is primarily the result of the fact that, barring satellite measurement, the only tool we have to detect distant atmospheres is through stellar occultation. Until recently, the techniques used in predicting and observing stellar occultations by KBOs has been ad hoc and imprecise, resulting in only scattered success. I will present a new technique my group has developed for accurate occultation predictions, a technique which has just recently been vetted. I will then discuss the power of occultations to detect and characterize the atmospheres, and discuss the dwarf planets of the Kuiper Belt, and their - likely varied - atmospheres, which have to date, avoided detection. I will finish by discussing the planned observations we will make at Gemini of three separate, and excellent looking occultation possibilities. I hope to impress that, with the use of the Acquisition-Cameras, Gemini presents the most powerful tool currently available for occultation work.