Coel Hellier c.hellier@keele.ac.uk
Helium in the eroding atmosphere of an exoplanet
Hellier
Authors
Abstract
Helium 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 1 . Searches for helium, however, have hitherto been unsuccessful 2 . 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 3 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 1010 to 3?×?1011 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.
Acceptance Date | Mar 9, 2018 |
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Publication Date | May 2, 2018 |
Journal | Nature |
Print ISSN | 1476-4687 |
Publisher | Nature Publishing Group |
Pages | 68 -70 |
DOI | https://doi.org/10.1038/s41586-018-0067-5 |
Publisher URL | http://doi.org/10.1038/s41586-018-0067-5 |
Files
20180517_heic1809a.pdf
(5.5 Mb)
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Publisher Licence URL
https://creativecommons.org/licenses/by-nc/4.0/
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