Dix Planetary Science Seminar
"Direct Characterization of Exoplanets with Long-Baseline Optical Interferometry"
By coherently interfering light from multiple telescopes, we can achieve angular resolutions that are orders of magnitude better than what can be achieved with current single dish telescopes. While interferometry has long been used the study the properties of bright stars, exoplanets are faint, making it difficult to maintain coherent interference in the presence of a turbulent atmosphere and fluctuations in the optical train. At the Very Large Telescope Interferometer (VLTI), we achieved the first detection of an exoplanet with long-baseline interferometry using the GRAVITY instrument and its dual-field capabilities where we can use the bright host star to maintain coherent interference of faint exoplanets over the course of minutes. We were able to measure the positions of exoplanets to 50 microarcsecond precision, a factor of 20 times better than what has been achieved on single dish telescopes. GRAVITY also uses the combination of adaptive optics and coherent rejection of starlight allows us to obtain high signal-to-noise K-band spectra of these exoplanets to measure their atmospheric composition. I will present some of our recent results with GRAVITY on studying the orbits and atmospheres of known exoplanets and future science potential with an upcoming survey.
"Characterizing Extrasolar Clouds in Polarized Light"
Current high-contrast imagers have enabled direct characterization of the atmospheres of young Jupiter-mass planets through multi-wavelength and spectroscopic measurements using light emitted by the planets themselves. The interpretation of these measurements relies on fitting the observations to atmospheric models, allowing us to estimate basic physical properties of these objects (e.g. effective temperature and surface gravity). However, comparisons between the observed data and model spectra have revealed that our understanding of cloud properties is incomplete and limits our ability to accurately infer the physical characteristics of these objects. Polarized light emitted by these objects provides an alternative observable that is sensitive to cloud properties and can provide critical inputs to these models. In this talk I will provide an introduction to using polarimetry to learn more about cloud properties in directly imaged planets and their free-floating analogs, brown dwarfs. I will summarize a recent detection of cloud banding in the nearby brown dwarf binary, Luhman 16AB, as well as preliminary results from the WIRC+Pol spectropolarimeter at Palomar.