Palomar WIRC+POL

Weather Reports for Exoplanets and Brown Dwarfs with Precision Spectro-Polarimetry at Palomar

Understanding clouds and weather in exoplanet and brown dwarf atmospheres is one of the most active and fascinating areas of research in the fast-moving field of extra-solar planetary system science. The stakes are high for two main reasons: clouds represent a crucial element of exoplanets and brown dwarf atmosphere dynamics, but they can also form a veil preventing us from remote sensing molecular species deeper in the atmosphere. Emitted light from cloudy exoplanet atmospheres can be highly polarized, while starlight itself is virtually unpolarized. When two images taken with orthogonal polarization filters are subtracted, unpolarized starlight is removed, revealing the polarized astrophysical signal, and providing a significant contrast gain. Polarimetry is still largely unexploited despite its information-rich content. Indeed, the direction and amplitude of the emergent polarization signal as a function of color and time enable detailed characterization of the composition, morphology, and dynamics of the scattering clouds. We integrated and commissioned a high precision near-infrared imaging low-resolution spectro-polarimeter mode for WIRC, the Prime focus wide-field infrared camera of the 200-inch Hale telescope on Mt Palomar, using a new technology called polarization grating. The 200-inch is the largest equatorial-Cassegrain telescope in operation. This configuration is optimal for high precision polarimetry since it introduces little and stable instrumental polarization. This endeavor will ultimately help us break through the veil of clouds in exoplanets and brown dwarfs, provide new and unique capabilities to Palomar. Other science cases include the study of SuperNovae, Solar system (e.g. asteroids), exoplanets, young stellar objects, etc.

Click here for our instrument paper. 

WIRC+Pol modulator upgrade

We recently upgraded WIRC+Pol with an achromatic halfwave plate modulator, boosting our polarimetric accuracy by an order of magnitude, resulting in <0.03% fractional polarization accuracy.

Co-investigators: Kaew Tinyanont (Caltech), Maxwell Millar-Blanchear (JPL/Caltech), Rebecca Jensen-Clem (UC Berkeley), Tiffany Kataria (JPL/Caltech), Heather Knutson (Caltech), Shreyas Vissapragada (Caltech), Rebecca Oppenheimer (AMNH), Ricky Nilsson (Caltech), Gautam Vasisht (JPL/Caltech), Eugene Serabyn (JPL/Caltech), Jennifer Milburn (Caltech), Nemanja Jovanovic (Caltech), Roger Smith (Caltech), Dave Hale (Caltech), and A.N. Ramaprakash (IUCAA).

© Dimitri Mawet 2017