As the number of detected extrasolar planets continues to rise, a particular subset provides unique opportunities for detailed investigations into the properties of the extrasolar planets themselves. The transmission spectrum of a transiting exoplanet, obtained by the comparison of observations taken in-transit with those taken out-of-transit, can be used to directly measure the effective radius of the exoplanet and its atmosphere or exosphere. Such measurements in strong optical transitions (e.g., Na I, K I) can be used to measure the atmospheric metallicity, rainout of condensates, distribution of stellar flux, and photoionization of atmospheric constituents.
Here, Dr. Redfield and his team will build upon their success in detecting the first atmosphere of a transiting exoplanet via transmission spectra. A recently granted large block of survey time on the 9.2-m Hobby Eberly telescope at the McDonald Observatory of the University of Texas at Austin will be used to expand their program to several other bright transiting exoplanets. This large-scale observational program is a major undertaking, and will require a nontrivial commitment to data reduction and analysis. Important issues that must be addressed include the removal of the telluric spectrum, a model of the contribution of differential stellar limb-darkening between the continuum and the cores of stellar lines, and an assessment of the contribution of systematic errors.
The main objective of this project is to measure the full optical transmission spectrum for several transiting exoplanets, and enable the first comparative study of exoplanetary atmospheric properties derived from transmission spectra. The resulting observational database will be very rich and will lead to several auxiliary research programs other than transmission spectroscopy, including stellar variability monitoring, reflected light searches, and stellar metallicity measurements.
To aid in the dissemination of the results, the McDonald Observatory Education and Public Outreach Office will work with Dr. Redfield to create a series of annual workshops. These workshops will be designed for fifteen secondary school teachers selected from a nationwide applicant pool, and will introduce them to the scientific issues related to extrasolar planets, their atmospheres, and the high spectral resolution observations used to study them. An extensive post-workshop evaluation will also take place in order to assess the effectiveness of the translation of activities developed in the workshop to the classroom.
This project seeks to measure the atmospheres of distant planets orbiting other stars, or exoplanets. We observed and studied gas giant planets, like Jupiter, but the techniques that we developed will be useful as we work to study the atmospheres of Earth-like planets in the future. We were able to observe the atmospheres of 6 other exoplanets and made a comparative study of the strongest spectral signatures, namely that of sodium and potassium. We also made an exciting discovery, the first detection of H-alpha, the strongest hydrogen line in the optical part of the electromagnetic spectrum. This is highly complementary to measurements of Lyman-alpha, the strongest hydrogen line in the ultraviolet part of the electromagnetic spectrum. Both will be used to understand the physical properties of the extended outer atmospheres of these planets, for which we had very little information on previously. Since many of these planets orbit very close to their host star (even closer than Mercury to our own Sun), these exoplanets have very substantial outer atmospheres heated by their proximity to their stars. This project led several secondary school teacher professional development workshops at McDonald Observatory, the site of the telescope that we used to make our scientific measurements. The Hobby-Eberly Telescope, a 9.2-meter diameter telescope is located at McDonald Observatory and provided hundreds of observations of our distant exoplanetary systems. The workshops were entitled, Worlds Beyond our Solar System. We worked with scores of science teachers from all over the country (from urban and rural schools, from all different age levels) to provide them tools and resources to bring back to their classrooms. Workshops included meeting with the scientists involved in the research, and touring and using the telescopes at the Observatory. The teachers bring their expertise and demonstrations back to many classrooms, often over the course of many years, thereby reaching hundreds to thousands of students across the country.
