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A low-mass planet candidate orbiting Proxima Centauri at a distance of 1.5 AU.

ABSTRACT: Our nearest neighbor, Proxima Centauri, hosts a temperate terrestrial planet. We detected in radial velocities evidence of a possible second planet with minimum mass m c sin i c = 5.8 ± 1.9M ⊕ and orbital period Pc=5.21-0.22+0.26 years. The analysis of photometric data and spectro-scopic activity diagnostics does not explain the signal in terms of a stellar activity cycle, but follow-up is required in the coming years for confirming its planetary origin. We show that the existence of the planet can be ascertained, and its true mass can be determined with high accuracy, by combining Gaia astrometry and radial velocities. Proxima c could become a prime target for follow-up and characterization with next-generation direct imaging instrumentation due to the large maximum angular separation of ~1 arc second from the parent star. The candidate planet represents a challenge for the models of super-Earth formation and evolution.

SUBMITTER: Damasso M

PROVIDER: S-EPMC6962037 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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A low-mass planet candidate orbiting Proxima Centauri at a distance of 1.5 AU.

Damasso Mario M Del Sordo Fabio F Anglada-Escudé Guillem G Giacobbe Paolo P Sozzetti Alessandro A Morbidelli Alessandro A Pojmanski Grzegorz G Barbato Domenico D Butler R Paul RP Jones Hugh R A HRA Hambsch Franz-Josef FJ Jenkins James S JS López-González María José MJ Morales Nicolás N Peña Rojas Pablo A PA Rodríguez-López Cristina C Rodríguez Eloy E Amado Pedro J PJ Amado Pedro J PJ Anglada Guillem G Feng Fabo F Gómez Jose F JF

Science advances 20200115 3

Our nearest neighbor, Proxima Centauri, hosts a temperate terrestrial planet. We detected in radial velocities evidence of a possible second planet with minimum mass m c sin i c = 5.8 ± 1.9M ⊕ and orbital period P c = 5.21 - 0.22 + 0.26 years. The analysis of photometric data and spectro-scopic activity diagnostics does not explain the signal in terms of a stellar activity cycle, but follow-up is required in the coming years for confirm ...[more]

PMID: 31998838

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Project description:Proxima Centauri b provides an unprecedented opportunity to understand the evolution and nature of terrestrial planets orbiting M dwarfs. Although Proxima Cen b orbits within its star's habitable zone, multiple plausible evolutionary paths could have generated different environments that may or may not be habitable. Here, we use 1-D coupled climate-photochemical models to generate self-consistent atmospheres for several evolutionary scenarios, including high-O2, high-CO2, and more Earth-like atmospheres, with both oxic and anoxic compositions. We show that these modeled environments can be habitable or uninhabitable at Proxima Cen b's position in the habitable zone. We use radiative transfer models to generate synthetic spectra and thermal phase curves for these simulated environments, and use instrument models to explore our ability to discriminate between possible planetary states. These results are applicable not only to Proxima Cen b but to other terrestrial planets orbiting M dwarfs. Thermal phase curves may provide the first constraint on the existence of an atmosphere. We find that James Webb Space Telescope (JWST) observations longward of 10 μm could characterize atmospheric heat transport and molecular composition. Detection of ocean glint is unlikely with JWST but may be within the reach of larger-aperture telescopes. Direct imaging spectra may detect O4 absorption, which is diagnostic of massive water loss and O2 retention, rather than a photosynthetic biosphere. Similarly, strong CO2 and CO bands at wavelengths shortward of 2.5 μm would indicate a CO2-dominated atmosphere. If the planet is habitable and volatile-rich, direct imaging will be the best means of detecting habitability. Earth-like planets with microbial biospheres may be identified by the presence of CH4-which has a longer atmospheric lifetime under Proxima Centauri's incident UV-and either photosynthetically produced O2 or a hydrocarbon haze layer. Key Words: Planetary habitability and biosignatures-Planetary atmospheres-Exoplanets-Spectroscopic biosignatures-Planetary science-Proxima Centauri b. Astrobiology 18, 133-189.

Dataset Information

A low-mass planet candidate orbiting Proxima Centauri at a distance of 1.5 AU.

Publications

A low-mass planet candidate orbiting Proxima Centauri at a distance of 1.5 AU.

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