Spectrally resolved helium absorption from the extended atmosphere of a warm Neptune exoplanet
Creators
- 1. Université de Genève
- 2. University of Exeter
- 3. Université de Genève, Leiden University
- 4. Université de Genève, Univ. di Padova, University of Amsterdam
- 5. University of Exeter, Johns Hopkins University
Description
Stellar heating causes atmospheres of close-in exoplanets to expand and escape. These extended atmospheres are difficult to observe because their main spectral signature – neutral hydrogen at ultraviolet wavelengths – is strongly absorbed by interstellar medium. We report the detection of the near-infrared triplet of neutral helium in the transiting warm Neptune-mass exoplanet HAT-P-11b using ground-based, high-resolution observations. The helium feature is repeatable over two independent transits, with an average absorption depth of 1.08±0.05%. Interpreting absorption spectra with 3D simulations of the planet’s upper atmosphere suggests it extends beyond 5 planetary radii, with a large scale height and a helium mass loss rate ≲ 3x105 g‧s−1. A net blueshift of the absorption might be explained by high-altitude winds flowing at 3 km‧s−1from day to night-side.
Files
Science_Allart_HAT-P-11b.zip
Files
(23.0 MB)
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