How hot is the inside of a young planet?
Abstract
We propose to test the following hypothesis: the gas-giant exoplanet WASP-107b is unusually inflated, and methane-depleted, because it is young, and therefore has a high internal temperature. If this is correct, the temperature throughout its atmosphere should be high enough for sodium and potassium to be in the gas phase, and show absorption signatures in WASP-107b's transmission spectrum. We therefore propose to use measurements of sodium and potassium as thermometers of WASP-107b's internal temperature. Our proposed observations will also tell us whether or not a low C/O ratio is required to explain the methane depletion previously observed for WASP-107b. This is useful because C/O ratios can tell us where planets form in their protoplanetary disks. WASP-107b is an outstanding target for atmospheric characterisation, which, combined with its apparent youth, makes it an ideal exoplanet for linking planet formation and evolution theories to observations of its present-day atmosphere. This kind of atmospheric archaeology has so far been difficult for individual planets. HST is the only telescope that can achieve the required precision and wavelength coverage to achieve our science goals.
- Publication:
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HST Proposal
- Pub Date:
- June 2019
- Bibcode:
- 2019hst..prop15838S