An absolute sodium abundance for a cloud-free 'hot Saturn' exoplanet.
Nature
; 557(7706): 526-529, 2018 05.
Article
en En
| MEDLINE
| ID: mdl-29736017
ABSTRACT
Broad absorption signatures from alkali metals, such as the sodium (Na I) and potassium (K I) resonance doublets, have long been predicted in the optical atmospheric spectra of cloud-free irradiated gas giant exoplanets1-3. However, observations have revealed only the narrow cores of these features rather than the full pressure-broadened profiles4-6. Cloud and haze opacity at the day-night planetary terminator are considered to be responsible for obscuring the absorption-line wings, which hinders constraints on absolute atmospheric abundances7-9. Here we report an optical transmission spectrum for the 'hot Saturn' exoplanet WASP-96b obtained with the Very Large Telescope, which exhibits the complete pressure-broadened profile of the sodium absorption feature. The spectrum is in excellent agreement with cloud-free, solar-abundance models assuming chemical equilibrium. We are able to measure a precise, absolute sodium abundance of logεNa = [Formula see text], and use it as a proxy for the planet's atmospheric metallicity relative to the solar value (Zp/ZÊ = [Formula see text]). This result is consistent with the mass-metallicity trend observed for Solar System planets and exoplanets10-12.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Tipo de estudio:
Prognostic_studies
Idioma:
En
Revista:
Nature
Año:
2018
Tipo del documento:
Article
País de afiliación:
Reino Unido