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dc.contributor.authorSpake, JJ
dc.contributor.authorSing, DK
dc.contributor.authorEvans, TM
dc.contributor.authorOklopčić, A
dc.contributor.authorBourrier, V
dc.contributor.authorKreidberg, L
dc.contributor.authorRackham, BV
dc.contributor.authorIrwin, J
dc.contributor.authorEhrenreich, D
dc.contributor.authorWyttenbach, A
dc.contributor.authorWakeford, HR
dc.contributor.authorZhou, Y
dc.contributor.authorChubb, KL
dc.contributor.authorNikolov, N
dc.contributor.authorGoyal, JM
dc.contributor.authorHenry, GW
dc.contributor.authorWilliamson, MH
dc.contributor.authorBlumenthal, S
dc.contributor.authorAnderson, DR
dc.contributor.authorHellier, C
dc.contributor.authorCharbonneau, D
dc.contributor.authorUdry, S
dc.contributor.authorMadhusudhan, N
dc.date.accessioned2018-05-08T13:39:23Z
dc.date.issued2018-05-02
dc.description.abstractHelium is the second-most abundant element in the Universe after hydrogen and is one of the main constituents of gas-giant planets in our Solar System. Early theoretical models predicted helium to be among the most readily detectable species in the atmospheres of exoplanets, especially in extended and escaping atmospheres. Searches for helium, however, have hitherto been unsuccessful. Here we report observations of helium on an exoplanet, at a confidence level of 4.5 standard deviations. We measured the near- infrared transmission spectrum of the warm gas giant WASP-107b and identified the narrow absorption feature of excited metastable helium at 10,833 angstroms. The amplitude of the feature, in transit depth, is 0.049 +/- 0.011 per cent in a bandpass of 98 angstroms, which is more than five times greater than what could be caused by nominal stellar chromospheric activity. This large absorption signal suggests that WASP-107b has an extended atmosphere that is eroding at a total rate of 10^10 to 3 x 10^11 grams per second (0.1-4 per cent of its total mass per billion years), and may have a comet-like tail of gas shaped by radiation pressure.en_GB
dc.description.sponsorshipWe thank S. Seager, A. Dupree, V. Andretta, M. Giampapa and B. Drummond for discussions. This work is based on observations made with the NASA/ESA HST, obtained at the Space Telescope Science Institute (STScI) operated by AURA, Inc. J.J.S. is supported by an STFC studentship. The research leading to these results has received funding from the European Research Council (ERC) under the European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement number 336792. Support for this work was provided by NASA grants under the HST-GO-14916 programme of the STScI. G.W.H. and M.H.W. acknowledge support from Tennessee State University and the State of Tennessee through its Centers of Excellence programme. The MEarth Team (J.I. and D.C.) gratefully acknowledges funding from the David and Lucille Packard Fellowship for Science and Engineering, the US National Science Foundation (NSF) and the John Templeton Foundation. The opinions expressed in this publication are those of the authors and do not necessarily reflect the views of the John Templeton Foundation. This work was carried out in the framework of the National Centre for Competence in Research PlanetS supported by the Swiss National Science Foundation (SNSF). V.B., D.E., A.W. and S.U. acknowledge financial support from the SNSF. D.E. and V.B. acknowledge funding from the ERC under the European Union’s Horizon 2020 research and innovation programme (project FOUR ACES; grant agreement No 724427). B.V.R acknowledges support from an NSF Graduate Research Fellowship (grant DGE-1746060) and the Earth in Other Solar Systems Team, NASA Nexus for Exoplanet System Science. IRAF is distributed by the National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the NSF. J.M.G. acknowledges support from a Leverhulme Trust Research Project Grant.en_GB
dc.identifier.citationVol. 557, No. 7703, pp. 68-70.en_GB
dc.identifier.doi10.1038/s41586-018-0067-5
dc.identifier.urihttp://hdl.handle.net/10871/32755
dc.language.isoenen_GB
dc.publisherNature Publishing Groupen_GB
dc.relation.sourceRaw HST data frames are publicly available online at the Mikulski Archive for Space Telescopes (MAST; https://archive.stsci.edu).en_GB
dc.rights.embargoreasonUnder embargo until 02 November 2018 in compliance with publisher policy.en_GB
dc.rights© 2018 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.en_GB
dc.subjectAtmospheric Chemistryen_GB
dc.subjectExoplanetsen_GB
dc.subjectGiant planetsen_GB
dc.titleHelium in the eroding atmosphere of an exoplaneten_GB
dc.typeArticleen_GB
dc.identifier.issn0028-0836
dc.descriptionThis is the author accepted manuscript. The final version is available from Nature Publishing Group via the DOI in this record.en_GB
dc.identifier.journalNatureen_GB


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