On a planet far, far away: Solving the inverse problem for extrasolar planets

Joanna Barstow

June 10, 2013

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Abstract: Visible and infrared remote sensing observations have provided a wealth of information about the planets in our solar system, including our own, over the last several decades. Space telescopes like Hubble, and future endeavours such as EChO (Exoplanet Characterisation Observatory) and JWST (James Webb Space Telescope), allow atmospheric retrieval techniques developed for solar system planets to be applied to spectroscopic observations of transiting exoplanets. However, poor signal-to-noise ratios, low numbers of observations per target and lack of ground truth make this a challenging problem to solve. This talk will discuss the methodology of atmospheric retrievals for exoplanets, what telescopes such as EChO might be able to achieve, and the limitations of remote sensing in the absence of constraints from in-situ measurements. Our close neighbour Venus provides a good example of how complex solving the inverse problem can be, even after detailed observation by a succession of dedicated spacecraft, and the super-Earth-sized exoplanet GJ 1214b is a ‘poster child’ for retrieval degeneracy and the challenges at low signal-to-noise.