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Delivery of Volatiles & Organics: From Earth to Exoearths in the Era of JWST

Spitzer Spectroscopy of Volatiles in the Inner Disks of T Tauri Stars

Presented by: John Carr (Naval Research Laboratory)
Category: Science Workshops   Duration: 25 minutes   Broadcast date: September 14, 2010
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One of the interesting results of the Spitzer mission is the observation that classical T Tauri stars (CTTS) show a rich molecular emission spectrum in the mid-infrared. The spectrum is typically dominated by rotational transitions of H2O, along with vibrational bands of simple organic molecules (HCN, C2H2 and CO2) and rotational transitions of OH. The spectra are well modeled with gas temperatures (300-700 K) and emitting area that are consistent with emission from a warm disk atmosphere at radii less than 2-3 AU, roughly inside the snow line for solar-mass stars and corresponding to the terrestrial planet zone in the Solar system. Furthermore, such emission is widespread among CTTS. These results demonstrate the ability of infrared molecular spectroscopy to probe volatiles in the inner disk and also indicate its potential to contribute to understanding the origin and evolution of water and organic molecules in the planet forming region of disks. While common, molecular emission is not detected among all CTTS; perhaps more interesting, a large disk-to-disk range is observed in the strength of the organic emission to water and in the flux ratios of the different organic bands. The cause of these variations and whether they represent true abundance differences are among the questions being addressed based on the significant body of Spitzer spectra of protoplanetary disks. The Spitzer data will also lay groundwork for spectroscopic studies with future facilities, including the JWST.