Dr. Richard Freedman
The discovery of extrasolar planets that periodically pass in front of their home stars – producing a mini-eclipse, or “transit” – has tantalized researchers with the possibility that by studying the starlight filtered through the atmosphere of these planets, they might learn what those envelopes of air contain. Astronomer Richard Freedman does the hard work of figuring out what the spectra of these alien atmospheres might be. This is a complex theoretical problem, especially given the high temperatures (often thousands of degrees) that a tightly-orbiting, transiting planet might have. A consequence of these toasty temperatures is that the spectra will be different from those that one can easily measure in the lab. Science has entered a new era in the study of planets, when the eight worlds of our own solar system have been augmented by hundreds more around other stars. This tally will continue to increase, and the intricate task of understanding the spectral signature of their atmospheres will eventually tell us how planets – of many types – are formed.
Projects
Molecular Spectroscopy, Modeling of Brown Dwarfs and Extrasolar Giant Planets
NNA05CS86A
Studies of Atomic and Molecular Opacity in Astrophysical Environments and the Application of Computer Modeling of Brown Dwarfs and Extra Solar Planets
NNX08AX97A
The field of brown dwarfs and extra solar giant planets is continuing to produce new and exciting research results. The number of known extra solar giant planets continues to grow with time and new discoveries. Currently there are almost three hundred extra solar planets known and more are being discovered as new observing techniques are devised. The Spitzer Infra Red Telescope (SIRTF) and large, ground based and airborne instruments such as SOFIA are currently being used, or will be, to discover and study new objects along with space observatories such as COROT and the upcoming Kepler mission. In order to make progress in understanding these objects it is necessary to construct detailed models so that their physical properties can be better understood. My own work is related to the calculation of atomic and molecular opacities for these objects that allows calculations of the properties of their atmospheres in order to interpret the observations and plan strategies for future work.
Using both laboratory data and theoretical calculations, I am establishing and maintaining large molecular databases for use in the opacity calculations that are essential for the modeling of the atmospheres of these objects. I then use the results of these calculations as input to various programs that compute line by line opacities for use in the models.
These opacity databases have been greatly extended as compared to the usual room temperature laboratory measurements. This is necessary as the room temperature databases have totally inadequate coverage for higher temperatures when excited levels far above the ground state become populated. My own work has used both laboratory and theoretical predictions to extend these databases. My pas experience in both laboratory and theoretical work allows me to apply the appropriate techniques to generate and prepare the data for use in my opacity programs. Currently, I am expecting new data to be available for species such as NH3, H2O, and CH4 in the near future. These updates will fill important gaps in our knowledge of these spectra.
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