An absolute sodium abundance for a cloud-free ‘hot Saturn’ exoplanet
Sing, D. K.
Fortney, J. J.
Goyal, J. M.
Evans, T. M.
Gibson, N. P.
De Mooij, E. J. W.
Wakeford, H. R.
Burgasser, A. J.
Mayne, N. J.
Carter, A. L.
Ballester, G. E.
Barstow, J. K.
Spake, J. J.
AffiliationUniv Arizona, Lunar & Planetary Lab
MetadataShow full item record
PublisherNATURE PUBLISHING GROUP
CitationNikolov, N., Sing, D. K., Fortney, J. J., Goyal, J. M., Drummond, B., Evans, T. M., ... & Smalley, B. (2018). An absolute sodium abundance for a cloud-free ‘hot Saturn’exoplanet. Nature, 557(7706), 526–529, doi:10.1038/s41586-018-0101-7
RightsCopyright © 2018, Springer Nature
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at email@example.com.
AbstractBroad 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 log epsilon(Na) = 6.9(-0.4)(+0.6), and use it as a proxy for the planet's atmospheric metallicity relative to the solar value (Z(p)/Z(circle dot) = 2.3(-1.7)(+8.9)). This result is consistent with the mass-metallicity trend observed for Solar System planets and exoplanets(10-12).
Note6 month embargo; published online: 07 May 2018
VersionFinal accepted manuscript
SponsorsEuropean Research Council under the European Union ; Leverhulme Trust Research Project Grant