A ground-based near-infrared emission spectrum of the exoplanet HD 189733b

摘要: Space-based infrared spectroscopy has successfully identified various molecules — H2O, CH4, CO2 and CO in the atmospheres of 'hot Jupiter' extrasolar planets. Swain et al. now report ground-based observations dayside emission spectrum hot Jupiter HD 189733b at near-infrared wavelengths not available to space-based telescopes. They find a bright feature ∼3.25 μm which is unexpected difficult explain using current models that assume local thermodynamic equilibrium conditions. Fluorescence from methane, similar seen Solar System planets, seems likely explanation. This work suggests atmospheric chemistry on exoplanets more complex than was thought, opens field exoplanet molecular Infrared can probe conditions compositions atmospheres. Previous results relied telescopes do provide spectroscopic capability 2.4–5.2 spectral region. Here, for are reported between 2.0–2.4 3.1–4.1 μm; an around 3.25 found with conditions, assigned methane. Detection probes Water (H2O), methane (CH4), carbon dioxide (CO2), monoxide (CO) have been detected1,2,3,4,5 two Jupiters. These previous 2.4–5.2 μm Here we HD 189733b 2.0–2.4 μm 3.1–4.1 μm, where feature. Where overlap instruments exists, our excellent agreement measurements2,6. A ∼3.25 μm (LTE) 1 bar 1 × 10-6 bar pressures typically sampled by measurements. The most explanation this it arises non-LTE what planets own System7,8,9. suggest effects may need be considered when interpreting measurements strongly irradiated exoplanets.