Collaborative Research: Extending Spectroscopy of Directly Imaged Planets into the Thermal Infrared

University Of California-Santa Cruz, Santa Cruz CA

Investigators

Abstract

New "integral field spectrographs" (IFS) allow astronomers to get spectra of exoplanets, or planets found around other stars. Until now, these spectra have covered wavelengths in the near infrared at 1 - 2 microns. Most gas-giant exoplanets generate their own power that peaks in energy in the thermal infrared at longer wavelengths. This research group has built the world's first thermal infrared IFS. The Arizona Lenslets for Exoplanet Spectroscopy (ALES) is installed on the 2x8.4m Large Binocular Telescope in Arizona. This project will use the ALES to obtain 3 - 4 micron spectra of 10 gas-giant exoplanets. The spectra will be combined with near-infrared spectra in order to compare and contrast the properties of the gas-giant exoplanets, including temperature, the properties of clouds, and different chemistry. This project serves the national interest by significantly advancing our scientific knowledge of the properties of gas-giant exoplanets. The investigators will teach two math classes each year at the Santa Cruz County Jail, so that each year, nine students will get college credit for a college algebra class. They will also talk about their science to the public. Adaptive optics integral field spectrographs (IFS) have enabled spectroscopic characterization of directly-imaged exoplanets. These instruments have, however, been limited to near-infrared wavelengths (1 - 2 microns), while the spectral energy distributions of gas giant exoplanets that generate their own spectral signal peak in the thermal infrared (>3 microns). As a result, most directly-imaged exoplanets already have near-infrared spectra, but none has a thermal infrared spectrum. Spectroscopic characterization over a broad wavelength range is critical for determining the bulk properties of extrasolar planets. This project will obtain 3 - 4 micron spectra of a large number of exoplanets, and, in the process, develop a cohesive sample of exoplanet spectra that can be used for comparative planetology. This research group has built the world's first thermal infrared IFS. The Arizona Lenslets for Exoplanet Spectroscopy (ALES) is installed on the 2x8.4m Large Binocular Telescope. It provides integral field spectroscopy from 3 - 4 microns at the spectral resolution, sensitivity and contrast levels required to characterize directly-imaged exoplanets. Using ALES, the investigators will obtain 3 - 4 micron spectra of 10 exoplanets, which they will analyze in combination with existing near-infrared data. The broad wavelength coverage will allow them to refine exoplanet atmosphere models by breaking degeneracies between temperature, cloud properties, and non-equilibrium chemistry. The investigators will offer two math classes per year at the Santa Cruz County Jail, resulting in ~9 students receiving college credit for a college algebra class. They will also include public talks on their science.