An absolute sodium abundance for a cloud-free 'hot Saturn' exoplanet.

Autor: Nikolov N; Physics and Astronomy, University of Exeter, Exeter, UK. nikolov.nkn@gmail.com., Sing DK; Physics and Astronomy, University of Exeter, Exeter, UK.; Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD, USA., Fortney JJ; Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA, USA., Goyal JM; Physics and Astronomy, University of Exeter, Exeter, UK., Drummond B; Physics and Astronomy, University of Exeter, Exeter, UK., Evans TM; Physics and Astronomy, University of Exeter, Exeter, UK., Gibson NP; Astrophysics Research Centre, School of Mathematics and Physics, Queens University Belfast, Belfast, UK., De Mooij EJW; School of Physical Sciences, Dublin City University, Glasnevin, Ireland.; Centre for Astrophysics & Relativity, Dublin City University, Glasnevin, Ireland., Rustamkulov Z; Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA, USA., Wakeford HR; Space Telescope Science Institute, Baltimore, MA, USA., Smalley B; Astrophysics Group, Keele University, Keele, UK., Burgasser AJ; Department of Physics, University of California, San Diego, CA, USA., Hellier C; Astrophysics Group, Keele University, Keele, UK., Helling C; Centre for Exoplanet Science, SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, UK.; Anton Pannekoek Institute for Astronomy, University of Amsterdam, Amsterdam, The Netherlands., Mayne NJ; Physics and Astronomy, University of Exeter, Exeter, UK., Madhusudhan N; Institute of Astronomy, University of Cambridge, Cambridge, UK., Kataria T; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA., Baines J; Astrophysics Research Centre, School of Mathematics and Physics, Queens University Belfast, Belfast, UK., Carter AL; Physics and Astronomy, University of Exeter, Exeter, UK., Ballester GE; Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA., Barstow JK; Physics and Astronomy, University College London, London, UK., McCleery J; Astrophysics Research Centre, School of Mathematics and Physics, Queens University Belfast, Belfast, UK., Spake JJ; Physics and Astronomy, University of Exeter, Exeter, UK.
Jazyk: angličtina
Zdroj: Nature [Nature] 2018 May; Vol. 557 (7706), pp. 526-529. Date of Electronic Publication: 2018 May 07.
DOI: 10.1038/s41586-018-0101-7
Abstrakt: 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 exoplanets 1-3 . However, observations have revealed only the narrow cores of these features rather than the full pressure-broadened profiles 4-6 . 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 abundances 7-9 . 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 logε Na  = [Formula: see text], and use it as a proxy for the planet's atmospheric metallicity relative to the solar value (Z p /Z ʘ  = [Formula: see text]). This result is consistent with the mass-metallicity trend observed for Solar System planets and exoplanets 10-12 .
Databáze: MEDLINE