| The study of planets outside of the solar system, known as exoplanets, is a very young field. Since the first discovery of an exoplanet in 1992 (and around a solar-type star in 1995), this field in astronomy has garnered much interest. The ultimate goal of discovering life elsewhere in the universe seems to be within reach, despite current technological limitations. First, the limits of current technology need to be found in order to see how limited such observations are using modern telescopes. Second, the atmospheres of exoplanets must be accurately described and modeled. To determine the detection limits, one can study the atmospheres of currently known exoplanets. These exoplanets are typically the mass of Jupiter, but are very close to their host stars, thus typically referred to as "hot" Jupiters. While these are not necessarily cradles of life, they represent advantageous testbeds of exoplanet atmospheres. Observations can constrain models and test the limits of current telescopes.; One such laboratory to test both observational limits and atmospheric models is the exoplanet HD 209458b, a transiting exoplanet. In particular, the molecule H+3 is a diagnostic of the thermal regulation in the ionosphere of the exoplanet, and therefore is an advantageous molecule to test both atmospheric models and observational limits. Recent observations of the transiting exoplanet HD 209458b have revealed evidence of sodium in the lower atmosphere and escaping hydrogen, carbon, and oxygen from the exosphere, providing new insight to the composition and physical processes relevant to short-period exoplanets.; The exoplanet HD 209458b was observed using Phoenix on Gemini South in 2005. The observations can constrain the physical conditions and photo-processing of the planet's atmosphere and characterize the gas that may currently be radiatively removed from it, as well as potentially provide insight to the interplay between the stellar and planetary magnetic fields. The observations represent significant and timely tests for both models of exoplanetary atmospheres and observational limits. |
