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1811071971024175104
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MIT
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© 2020, The Author(s), under exclusive licence to Springer Nature Limited. About 1 out of 200 Sun-like stars has a planet with an orbital period shorter than one day: an ultrashort-period planet1,2. All of the previously known ultrashort-period planets are either hot Jupiters, with sizes above 10 Earth radii (R⊕), or apparently rocky planets smaller than 2 R⊕. Such lack of planets of intermediate size (the ‘hot Neptune desert’) has been interpreted as the inability of low-mass planets to retain any hydrogen/helium (H/He) envelope in the face of strong stellar irradiation. Here we report the discovery of an ultrashort-period planet with a radius of 4.6 R⊕ and a mass of 29 M⊕, firmly in the hot Neptune desert. Data from the Transiting Exoplanet Survey Satellite3 revealed transits of the bright Sun-like star LTT 9779 every 0.79 days. The planet’s mean density is similar to that of Neptune, and according to thermal evolution models, it has a H/He-rich envelope constituting 9.0−2.9+2.7% of the total mass. With an equilibrium temperature around 2,000 K, it is unclear how this ‘ultrahot Neptune’ managed to retain such an envelope. Follow-up observations of the planet’s atmosphere to better understand its origin and physical nature will be facilitated by the star’s brightness (Vmag = 9.8).
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2024-09-23T08:58:51Z
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Article
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mit-1721.1/133848
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Massachusetts Institute of Technology
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English
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2024-09-23T08:58:51Z
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2021
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Springer Science and Business Media LLC
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dspace
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mit-1721.1/1338482021-10-28T04:50:21Z An ultrahot Neptune in the Neptune desert © 2020, The Author(s), under exclusive licence to Springer Nature Limited. About 1 out of 200 Sun-like stars has a planet with an orbital period shorter than one day: an ultrashort-period planet1,2. All of the previously known ultrashort-period planets are either hot Jupiters, with sizes above 10 Earth radii (R⊕), or apparently rocky planets smaller than 2 R⊕. Such lack of planets of intermediate size (the ‘hot Neptune desert’) has been interpreted as the inability of low-mass planets to retain any hydrogen/helium (H/He) envelope in the face of strong stellar irradiation. Here we report the discovery of an ultrashort-period planet with a radius of 4.6 R⊕ and a mass of 29 M⊕, firmly in the hot Neptune desert. Data from the Transiting Exoplanet Survey Satellite3 revealed transits of the bright Sun-like star LTT 9779 every 0.79 days. The planet’s mean density is similar to that of Neptune, and according to thermal evolution models, it has a H/He-rich envelope constituting 9.0−2.9+2.7% of the total mass. With an equilibrium temperature around 2,000 K, it is unclear how this ‘ultrahot Neptune’ managed to retain such an envelope. Follow-up observations of the planet’s atmosphere to better understand its origin and physical nature will be facilitated by the star’s brightness (Vmag = 9.8). 2021-10-27T19:56:59Z 2021-10-27T19:56:59Z 2020 2021-09-21T18:14:50Z Article http://purl.org/eprint/type/JournalArticle https://hdl.handle.net/1721.1/133848 en 10.1038/S41550-020-1142-Z Nature Astronomy Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf Springer Science and Business Media LLC arXiv
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| spellingShingle |
An ultrahot Neptune in the Neptune desert
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| title |
An ultrahot Neptune in the Neptune desert
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| title_full |
An ultrahot Neptune in the Neptune desert
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| title_fullStr |
An ultrahot Neptune in the Neptune desert
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| title_full_unstemmed |
An ultrahot Neptune in the Neptune desert
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| title_short |
An ultrahot Neptune in the Neptune desert
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| title_sort |
ultrahot neptune in the neptune desert
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| url |
https://hdl.handle.net/1721.1/133848
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