PALS: William Balmer (JHU), High contrast imaging with JWST

High contrast imaging with JWST

William Balmer
Ph.D. Candidate
Johns Hopkins University
Space Telescope Science Institute

Abstract: The formation and evolution of giant planets is still observationally uncertain. Do the most massive planets form top down like stars and brown dwarfs, or bottom up from the accretion of smaller bodies? Once they’ve formed, how do giant planets dynamically interact, and reshape their solar systems? High contrast observations from JWST can reveal key compositional clues in the spectra of giant planets, and can image colder, older, and more wild planets than seen before. 

I will present my team’s novel observations of giant planets with JWST’s coronagraphs. We used the telescope improperly, on purpose, to image the HR 8799 and 51 Eri planetary systems in a whole new light. Our set of filters captured the first direct images of CO2 in an exoplanet’s atmosphere, and constrained the metallicity of these planet’s atmospheres largely independent of the cloud and mixing degeneracies that have hampered previous ground based measurements. The HR 8799 planets appear to display a sequence of colors correlated with their orbital separation. This could indicate these massive, widely separated giants formed via core/pebble accretion, but more importantly, the large solid accretion implied by their high metallicity implies formation at young ages within the parent disk.

I will also present my team’s observations of the coldest and oldest planets yet imaged, in particular, our image of 14 Herculis c, a cold (275K) giant in a dynamically hot system. These observations not only reveal the unique chemistry in cold atmospheres, but the intense dynamics at play in multi-giant planet systems.

Host: Hayley Beltz