PI: Christine Chen
cchen@stsci.edu; https://www.stsci.edu/~cchen/STScI/; 410 338 5087
Project Duration: 1 year, with much potential to grow into a thesis project
Project Abstract:
Intro: Debris disks are dusty disks around main sequence stars. Unlike protoplanetary disks, the dust and gas in these systems is believed to be created in collisions among extrasolar planetesimals (analogous to asteroids and comets in our own Solar System), planetary embryos, and planets. I use multi-wavelength techniques to study the properties of dust and gas in these systems to understand whether events that have occurred in our Solar System's history are common or rare. I participate in two research groups at STScI: (1) Extrasolar Planetary Systems Imaging Group (EPSIG) and (2) Star and Planet Formation (SPF) research group.
At the current time, I am leading efforts to study debris disks using two facilities. I am the Principal Investigator for a Gemini Observatory Large and Long Program "Characterizing Dusty Debris in Exoplanetary Systems" that obtained deep, multi-filter Gemini Planet Imager (GPI) Spec and Pol observations of a dozen debris disks. These observations can be used to characterize asymmetries in the structures of the disks that indicate the presence of undetected planets. They can also be used to estimate the size of the smallest dust grains, their shapes (fluffy aggregates versus solid spheres), and compositions. More recently, I am looking forward to the launch of JWST. I have a JWST Guaranteed Time Observations program (described in Project 1) and a recently accepted Cycle 1 General Observer program.
Project 1: Thermal Emission Spectroscopy with JWST. I am a JWST Mid-infrared Instrument (MIRI) Scientist with Guaranteed Time Observations in Cycle 1. I have reserved MIRI Medium Resolution Spectrograph (MRS) observations of three nearby, archetypal debris disk systems: beta Pictoris, eta Crv, and eta Tel. The MIRI MRS is an integral field spectrograph that provides mid-infrared spectra (5-30 micron) and therefore access to silicate dust features (e.g. silica, olivine, pyroxene) and atomic and molecular gas features (e.g. H2O, CO2, HCN). All three systems have silicate emission features that were detected using the Spitzer Infrared Spectrograph and CO emission detected using ALMA, indicating that they possess both terrestrial temperature dust and massive Kuiper Belts containing icy bodies. Thus, some of the science goals for this program include searching for changes in the silicate properties since the Spitzer observations (to indicate ongoing collisions) and conducting the first sensitive search for terrestrial temperature volatile gas. The detection of terrestrial temperature gas might indicate that there are undetected planets that are dynamically perturbing KBOs into the inner regions of the planetary systems.
Project 2: The beta Pic b Exoplanetary Atmosphere. The beta Pic observations can also be used to study the atmosphere of the exoplanet beta Pic b. The MIRI MRS observations will be obtained at a time when beta Pic b is near greatest elongation, enabling the extraction of the first mid-infrared spectrum for this companion. Based on atmospheric modeling of ground-based photometric measurements, the beta Pic b atmosphere is expected to contain silicate particles whose features the MIRI MRS data could detect for the first time. Extraction of the beta Pic b spectrum will require the use of high contrast imaging techniques, such as reference PSF subtraction. This work would be carried out in collaboration with the STScI Extrasolar Planetary Systems Imaging Group (including Drs. Marshall Perrin, Laurent Pueyo, Julien Girard) and the MIRI Instrument Team (including Drs. Dean Hines and David Law).
