Spectroscopy Insights into Giant Planet Atmospheres: Advances and Future Directions
This review by Jonathan Fortney explores the advancements in spectroscopy of giant planets, highlighting the need for improved instruments to analyze atmospheric characteristics. It discusses the significance of methane in mid-infrared absorptions and the challenges of interpreting broad broadband data across numerous planets. The review examines factors affecting atmospheric compositions, such as planet mass and stellar type, and aims to connect molecular abundances to planetary formation theories. Emphasis is placed on the importance of the James Webb Space Telescope (JWST) for discovering unknown atmospheric species.
Spectroscopy Insights into Giant Planet Atmospheres: Advances and Future Directions
E N D
Presentation Transcript
Spectroscopy of Giant Planets Jonathan Fortney University of California, Santa Cruz PPVI Review: Madhusudhan, Knutson, Fortney, & Barman arXiv:1402.1169 JWST Transit Planets Meeting
We’re 40-45 years behind work in the Solar System Jupiter Gillett, Low, & Stein (1969) • CH4 dominant mid IR absorber • Temperature inversion from 7.8 mm CH4 band • Bright at 5 mm – high Tbright Lee et al. (2012)
The Past Ten Years of Atmospheric Characterization Line et al. (2013) • We’ve been trying very hard to make progress using instruments that were not designed for our uses • We’ve gathered somewhat imprecise broadband data for dozen of planets
High S/N data over a broad wavelength range fundamentally changes the kinds of questions we can ask and answer Line et al. (2013)
Giant Planet Spectroscopy • We are not merely tying up loose ends – it is not even close to that! • Is atmospheric metal-enrichment a hallmark of giant planets? • How does this change with: • Planet mass • Stellar type • Migration history • Do giant planets share the abundance ratios of their parent star? • Jupiter is quasi-consistent with 2-4x solar • How important is disk condensation (snow lines) in leading to deviations in abundances?
Atmospheric Physics and Chemistry • How significantly do atmospheres deviate from radiative • equilibrium (energy sources and sinks) • How is day-night temperature homogenization affected by: • Incident flux • Surface gravity • Atmospheric metallicity • Rotation rate • What is the role of cloud opacity? • Does it effect emitted spectra as well as transit spectra? • Can we figure out what the cloud compositions are? • Chemistry • Role of deviations from equilibrium chemistry • Homogenization due to vertical and or horizontal mixing
Broad JWST coverage over molecules of interest Shabram et al. (2011) • We’d like to know the abundances of these molecules within a factor of ~5-10 • Would allow connection to planet formation
Broad JWST coverage over molecules of interest from a C/O ratio or photochemical perspective Shabram et al. (2011)
The Unknown Unknowns: Our imperfect understanding of these atmospheres, in the absence of spectral data ? • Phosphorus compounds? • Sulfur compounds? • I don’t know (that’s why they’re called unknown unknowns)
Excellent Recent Progress with HST WFC3 Transmission Emission WASP-43b Kreidberg, Line, Stevenson, Bean, others, et al. (in prep) Deming et al. (2013) Also: Precision of ~20-30 ppm for transmission spectra: Kreidberg et al., Knutson et al.
Model Atmospheres are Rounding into Shape WASP-19b Fortney Burrows WASP-19b Huitson et al. (2013) • A major concern of mine over the past 5 years has been the lack of comparisons between modeling groups • This is still imperfect but has gotten a lot better • Some groups have honed their R-T, chemistry, and clouds on brown dwarf spectra across a wide Teff range Deming Fortney
Fundamental Assumption • 1D techniques, including retrieval techniques, aim to understand hemispheric average conditions • Patchy clouds on planets may be a problem? • Non uniform transiting planet day sides may be a bigger problem? Day Night HD 189733b, Dobbs-Dixon et al. (2013) HD 189733b, Showman et al. (2009)
