Absorption Spectra of the Prototype Hot-Jupiters: determination of atmospheric constituents and structure

Abstract

Abstract. The two prototype hot-Jupiter exoplanets HD209458b and HD189733b are currently offering an unprecedented view of their atmospheres. As discussed here, primary transit transmission spectra provide the opportunity to identify specific atomic and molecular species, determine their abundances, and recover temperature-pressure-altitude information. We present a reanalysis of existing HST/STIS data on HD209458b, providing a complete optical transmission spectrum. Analysis of this spectrum have revealed: (1) the planetary abundance of sodium which is ∼2X solar (2) a depletion of sodium at high altitudes due to condensation or ionization (3) Rayleigh scattering by H 2 (3) a high temperature at pressures of 10's mbar consistent with the dayside inversion (4) a separate high-altitude hot temperature from the planet's thermosphere and (5) likely absorption by TiO/VO. While HD209458b and HD189733b are currently the best candidates for these studies, another ∼10 exoplanets are good targets with today's instruments for future transmission-based atmospheric detections.

Determining habitability: which exoEarths should we search for life?

“…Recent studies claiming to have detected the first molecules in the atmospheres of hot Jupiters have required significant investment in telescope time (e.g. Sing et al 2008). To detect life-indicating molecules in the atmospheres of an exoEarth would clearly be significantly more challenging, although some of that difficulty will obviously be ameliorated by the development of new technology and the next generation of space telescopes.…”