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Detection of titanium oxide in the atmosphere of a hot Jupiter

Nature volume 549, pages 238241 (14 September 2017) | Download Citation

Abstract

As an exoplanet transits its host star, some of the light from the star is absorbed by the atoms and molecules in the planet’s atmosphere, causing the planet to seem bigger; plotting the planet’s observed size as a function of the wavelength of the light produces a transmission spectrum1. Measuring the tiny variations in the transmission spectrum, together with atmospheric modelling, then gives clues to the properties of the exoplanet’s atmosphere. Chemical species composed of light elements—such as hydrogen, oxygen, carbon, sodium and potassium—have in this way been detected in the atmospheres of several hot giant exoplanets2,3,4,5, but molecules composed of heavier elements have thus far proved elusive. Nonetheless, it has been predicted that metal oxides such as titanium oxide (TiO) and vanadium oxide occur in the observable regions of the very hottest exoplanetary atmospheres, causing thermal inversions on the dayside6,7. Here we report the detection of TiO in the atmosphere of the hot-Jupiter planet WASP-19b. Our combined spectrum, with its wide spectral coverage, reveals the presence of TiO (to a confidence level of 7.7σ), a strongly scattering haze (7.4σ) and sodium (3.4σ), and confirms the presence of water (7.9σ) in the atmosphere5,8.

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Acknowledgements

This work is based on observations made with the FORS2 instrument on the European Southern Observatory (ESO)’s VLT. We thank staff astronomers J. Anderson and J. Smoker for performing some of the observations. E.S. acknowledges support from the ESO through the studentship programme. R.J.M. and S.G. acknowledge financial support from the UK Science and Technology Facilities Council (STFC) towards their doctoral programmes. M.O. acknowledges research funding from the Deutsche Forschungsgemeinschaft (DFG), grant OS 508/1-1, as well as support from the Fundação para a Ciência e a Tecnologia (FCT) through national funds and from FEDER through COMPETE2020 from the following grants: UID/FIS/04434/2013 and POCI-01-0145-FEDER-007672; and PTDC/FIS-AST/1526/2014 and POCI-01-0145-FEDER-016886. We thank the Spanish Ministry of Education and Science (MEC; grants AYA2015-71718-R and ESP2015-65712-C5-5-R) for support during the development of this work. We also thank the referees for their comments, which improved the manuscript.

Author information

Affiliations

  1. European Southern Observatory, Alonso de Córdova 3107, Santiago, Chile

    • Elyar Sedaghati
    •  & Henri M. J. Boffin
  2. Deutsches Zentrum für Luft- und Raumfahrt, Rutherfordstrasse 2, 12489 Berlin, Germany

    • Elyar Sedaghati
    •  & Heike Rauer
  3. Zentrum für Astronomie und Astrophysik, TU Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany

    • Elyar Sedaghati
    •  & Heike Rauer
  4. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK

    • Ryan J. MacDonald
    • , Siddharth Gandhi
    •  & Nikku Madhusudhan
  5. Astrophysics Research Centre, School of Mathematics and Physics, Queens University Belfast, Belfast BT7 1NN, UK

    • Neale P. Gibson
  6. Institut für Astrophysik, Georg-August Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany

    • Mahmoudreza Oshagh
  7. Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal

    • Mahmoudreza Oshagh
  8. Instituto de Astrofísica de Andalucía, CSIC, Apartado 3004, 18080 Granada, Spain

    • Antonio Claret

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Contributions

E.S. and H.M.J.B. led the scientific proposal, observational campaigns, data reduction and analysis up to the production of transmission spectra. R.J.M. conducted the atmospheric retrieval and S.G. generated the absorption cross-sections, both under the supervision of N.M., who planned and oversaw the atmospheric analyses and theoretical interpretation. N.P.G. wrote the python modules for the Gaussian process and the Monte Carlo Markov Chain analysis. M.O. analysed the impact of unocculted stellar active regions. A.C. calculated the theoretical limb-darkening coefficients for the specific bandpasses. H.R. provided feedback on the manuscript and is involved in the supervision of E.S. All authors contributed to writing the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Elyar Sedaghati.

Reviewer Information Nature thanks K. Heng and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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DOI

https://doi.org/10.1038/nature23651

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