Speaker
Dr
Caroline Morley
(Harvard University)
Description
The formation of clouds and hazes in exoplanet and brown dwarf atmospheres shapes their observed spectra. The species that condense readily in these atmospheres range from the common, like water and ammonia ices, to the more obscure, like sodium sulfide and potassium chloride. One of the most important dust species is silicate, including enstatite and forsterite. Optical properties for these species are required in order to model their effect on the emergent spectra of these objects. Some of these optical properties are well-constrained, but others are less well measured and are currently included in models using interpolation to fill in gaps in wavelength coverage. As the JWST era approaches, we will probe infrared wavelengths with interesting spectral features, including silicates at ~10 microns as well as various oxide and sulfide species. Accurately determined optical properties will aid in the interpretation of long-wavelength spectra of these objects; it is possible that spectra from JWST will allow us to directly measure the compositions of some of these exoplanet and brown dwarf clouds using their vibrational features. The photochemical hazes that may form in warm exoplanet atmospheres have particularly poor constraints on their optical properties. While proxies for Titan’s hazes have been created and studied in the lab, the hazes that form in exoplanets will naturally look quite different, as they are species that condense at much hotter temperatures than Titan’s haze. Since many planets large and small appear to have hazy atmospheres, this is an area that requires much more study. Lab experiments are needed to determine first what the composition of these hazes is likely to be, and then determine their indices of refraction across a broad wavelength range.
Primary author
Dr
Caroline Morley
(Harvard University)
