Colloquium
Comparative
Exoplanetology: Observing the Atmospheres of Transiting Exoplanets
Dr. Seth Redfield
Department of Astronomy
University of Texas
Tuesday, February
26, 2008,
1:40 p.m., SCIC 126
High signal-to-noise ratio (S/N) and high spectral
resolution observations of transiting exoplanets provide an opportunity to measure
the properties of exoplanet atmospheres and exospheres through transmission
spectroscopy. I will present the results of a large-scale program which led
to the first ground-based detection of absorption due to an exoplanetary
atmosphere. Observations were taken with the Hobby-Eberly Telescope (HET),
which is well suited for this type of program given its large mirror, high
resolution spectrograph, and queue scheduling. We observe significant
additional absorption in the cores of the neutral sodium doublet relative
to the continuum, when in-transit observations are compared to
out-of-transit observations. Two tests are performed to confirm the
detection: (1) analysis of a strong control line that is predicted to show
no absorption, and (2) an empirical Monte Carlo
analysis to quantify the impact of systematic errors. Physical properties
of the exoplanet atmosphere, such as atomic and molecular composition,
cloud altitudes, and wind speeds may be derived from the transmission
spectrum. I will discuss the richness of the acquired datasets and describe
several complimentary research projects, including some which could utilize
College of Charleston facilities. Such future observational programs will
make direct comparisons of the physical characteristics of exoplanet
atmospheres possible, enabling studies in comparative exoplanetology.
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