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Line MR, Brogi M, Bean JL, Gandhi S, Zalesky J, Parmentier V, Smith P, Mace GN, Mansfield M, Kempton EMR, Fortney JJ, Shkolnik E, Patience J, Rauscher E, Désert JM, Wardenier JP. A solar C/O and sub-solar metallicity in a hot Jupiter atmosphere. Nature 2021; 598:580-584. [PMID: 34707303 DOI: 10.1038/s41586-021-03912-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 08/13/2021] [Indexed: 11/09/2022]
Abstract
Measurements of the atmospheric carbon (C) and oxygen (O) relative to hydrogen (H) in hot Jupiters (relative to their host stars) provide insight into their formation location and subsequent orbital migration1,2. Hot Jupiters that form beyond the major volatile (H2O/CO/CO2) ice lines and subsequently migrate post disk-dissipation are predicted have atmospheric carbon-to-oxygen ratios (C/O) near 1 and subsolar metallicities2, whereas planets that migrate through the disk before dissipation are predicted to be heavily polluted by infalling O-rich icy planetesimals, resulting in C/O < 0.5 and super-solar metallicities1,2. Previous observations of hot Jupiters have been able to provide bounded constraints on either H2O (refs. 3-5) or CO (refs. 6,7), but not both for the same planet, leaving uncertain4 the true elemental C and O inventory and subsequent C/O and metallicity determinations. Here we report spectroscopic observations of a typical transiting hot Jupiter, WASP-77Ab. From these, we determine the atmospheric gas volume mixing ratio constraints on both H2O and CO (9.5 × 10-5-1.5 × 10-4 and 1.2 × 10-4-2.6 × 10-4, respectively). From these bounded constraints, we are able to derive the atmospheric C/H ([Formula: see text] × solar) and O/H ([Formula: see text] × solar) abundances and the corresponding atmospheric carbon-to-oxygen ratio (C/O = 0.59 ± 0.08; the solar value is 0.55). The sub-solar (C+O)/H ([Formula: see text] × solar) is suggestive of a metal-depleted atmosphere relative to what is expected for Jovian-like planets1 while the near solar value of C/O rules out the disk-free migration/C-rich2 atmosphere scenario.
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Affiliation(s)
- Michael R Line
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA. .,NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, WA, USA.
| | - Matteo Brogi
- Department of Physics, University of Warwick, Coventry, UK.,Centre for Exoplanets and Habitability, University of Warwick, Coventry, UK.,INAF-Osservatorio Astrofisico di Torino, Turin, Italy
| | - Jacob L Bean
- Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL, USA
| | - Siddharth Gandhi
- Department of Physics, University of Warwick, Coventry, UK.,Centre for Exoplanets and Habitability, University of Warwick, Coventry, UK
| | - Joseph Zalesky
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
| | - Vivien Parmentier
- Atmospheric, Oceanic, and Planetary Physics, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK
| | - Peter Smith
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
| | - Gregory N Mace
- Department of Astronomy, University of Texas at Austin, Austin, TX, USA
| | - Megan Mansfield
- Department of Geophysical Sciences, University of Chicago, Chicago, IL, USA
| | - Eliza M-R Kempton
- Department of Astronomy, University of Maryland, College Park, MD, USA
| | - Jonathan J Fortney
- Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA, USA
| | - Evgenya Shkolnik
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA.,NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, WA, USA
| | - Jennifer Patience
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
| | - Emily Rauscher
- Department of Astronomy, University of Michigan, Ann Arbor, MI, USA
| | - Jean-Michel Désert
- Anton Pannekoek Institute for Astronomy, University of Amsterdam, Amsterdam, the Netherlands
| | - Joost P Wardenier
- Atmospheric, Oceanic, and Planetary Physics, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK
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2
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Gaseous atomic nickel in the coma of interstellar comet 2I/Borisov. Nature 2021; 593:375-378. [PMID: 34012084 DOI: 10.1038/s41586-021-03485-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2020] [Accepted: 03/23/2021] [Indexed: 11/08/2022]
Abstract
On 31 August 2019, an interstellar comet was discovered as it passed through the Solar System (2I/Borisov). On the basis of initial imaging observations, 2I/Borisov seemed to be similar to ordinary Solar System comets1,2-an unexpected characteristic given the multiple peculiarities of the only known previous interstellar visitor, 1I/'Oumuamua3-6. Spectroscopic investigations of 2I/Borisov identified the familiar cometary emissions from CN (refs. 7-9), C2 (ref. 10), O I (ref. 11), NH2 (ref. 12), OH (ref. 13), HCN (ref. 14) and CO (refs. 14,15), revealing a composition similar to that of carbon monoxide-rich Solar System comets. At temperatures greater than 700 kelvin, comets also show metallic vapours that are produced by the sublimation of metal-rich dust grains16. Observation of gaseous metals had until very recently17 been limited to bright sunskirting and sungrazing comets18-20 and giant star-plunging exocomets21. Here we report spectroscopic observations of atomic nickel vapour in the cold coma of 2I/Borisov at a heliocentric distance of 2.322 astronomical units-equivalent to an equilibrium temperature of 180 kelvin. Nickel in 2I/Borisov seems to originate from a short-lived nickel-containing molecule with a lifetime of [Formula: see text] seconds at 1 astronomical unit and is produced at a rate of 0.9 ± 0.3 × 1022 atoms per second, or 0.002 per cent relative to OH and 0.3 per cent relative to CN. The detection of gas-phase nickel in the coma of 2I/Borisov is in line with the recent identification of this atom-as well as iron-in the cold comae of Solar System comets17.
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Abstract
Ultra-hot giant exoplanets receive thousands of times Earth’s
insolation1,2. Their high-temperature
atmospheres (>2,000 K) are ideal laboratories for studying extreme
planetary climates and chemistry3–5. Daysides
are predicted to be cloud-free, dominated by atomic species6 and substantially hotter than
nightsides5,7,8. Atoms are expected to recombine into molecules over the
nightside9, resulting
in different day-night chemistry. While metallic elements and a large
temperature contrast have been observed10–14, no
chemical gradient has been measured across the surface of such an exoplanet.
Different atmospheric chemistry between the day-to-night
(“evening”) and night-to-day (“morning”) terminators
could, however, be revealed as an asymmetric absorption signature during
transit4,7,15. Here, we report the detection of an asymmetric
atmospheric signature in the ultra-hot exoplanet WASP-76b. We spectrally and
temporally resolve this signature thanks to the combination of high-dispersion
spectroscopy with a large photon-collecting area. The absorption signal,
attributed to neutral iron, is blueshifted by −11±0.7 km
s-1 on the trailing limb, which can be explained by a combination
of planetary rotation and wind blowing from the hot dayside16. In contrast, no signal arises
from the nightside close to the morning terminator, showing that atomic iron is
not absorbing starlight there. Iron must thus condense during its journey across
the nightside.
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Helling C, Rimmer PB. Lightning and charge processes in brown dwarf and exoplanet atmospheres. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2019; 377:20180398. [PMID: 31378171 PMCID: PMC6710897 DOI: 10.1098/rsta.2018.0398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The study of the composition of brown dwarf atmospheres helped to understand their formation and evolution. Similarly, the study of exoplanet atmospheres is expected to constrain their formation and evolutionary states. We use results from three-dimensional simulations, kinetic cloud formation and kinetic ion-neutral chemistry to investigate ionization processes that will affect their atmosphere chemistry: the dayside of super-hot Jupiters is dominated by atomic hydrogen, and not H2O. Such planetary atmospheres exhibit a substantial degree of thermal ionization and clouds only form on the nightside where lightning leaves chemical tracers (e.g. HCN) for possibly long enough to be detectable. External radiation may cause exoplanets to be enshrouded in a shell of highly ionized, H3+-forming gas and a weather-driven aurora may emerge. Brown dwarfs enable us to study the role of electron beams for the emergence of an extrasolar, weather system-driven aurora-like chemistry, and the effect of strong magnetic fields on cold atmospheric gases. Electron beams trigger the formation of H3+ in the upper atmosphere of a brown dwarf (e.g. LSR-J1835), which may react with it to form hydronium, H3O+, as a longer lived chemical tracer. Brown dwarfs and super-hot gas giants may be excellent candidates to search for H3O+ as an H3+ product. This article is part of a discussion meeting issue 'Advances in hydrogen molecular ions: H3+, H5+ and beyond'.
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Affiliation(s)
- Christiane Helling
- Centre for Exoplanet Science, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK
- SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
- e-mail:
| | - Paul B. Rimmer
- Department of Earth Sciences, University of Cambridge, Downing St, Cambridge CB2 3EQ, UK
- Cavendish Astrophysics, JJ Thomson Ave, Cambridge CB3 0HE, UK
- MRC Laboratory of Molecular Biology, Francis Crick Ave, Cambridge CB2 0QH, UK
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