AI Article Synopsis

  • Researchers discovered an Earth-sized exoplanet, LP 791-18d, orbiting the cool M6 dwarf star LP 791-18, which has a radius of 1.03 times that of Earth and an equilibrium temperature of 300-400 K, potentially supporting water condensation.
  • The planetary system includes a sub-Neptune, LP 791-18c, which retains a gas envelope, and their gravitational interactions prevent LP 791-18d's orbit from becoming fully circular, leading to ongoing tidal heating.
  • This discovery offers a unique opportunity to study the conditions that could allow an exoplanet to maintain a hospitable climate amidst volcanic activity and other geological processes.

Article Abstract

Temperate Earth-sized exoplanets around late-M dwarfs offer a rare opportunity to explore under which conditions planets can develop hospitable climate conditions. The small stellar radius amplifies the atmospheric transit signature, making even compact secondary atmospheres dominated by N or CO amenable to characterization with existing instrumentation. Yet, despite large planet search efforts, detection of low-temperature Earth-sized planets around late-M dwarfs has remained rare and the TRAPPIST-1 system, a resonance chain of rocky planets with seemingly identical compositions, has not yet shown any evidence of volatiles in the system. Here we report the discovery of a temperate Earth-sized planet orbiting the cool M6 dwarf LP 791-18. The newly discovered planet, LP 791-18d, has a radius of 1.03 ± 0.04 R and an equilibrium temperature of 300-400 K, with the permanent night side plausibly allowing for water condensation. LP 791-18d is part of a coplanar system and provides a so-far unique opportunity to investigate a temperate exo-Earth in a system with a sub-Neptune that retained its gas or volatile envelope. On the basis of observations of transit timing variations, we find a mass of 7.1 ± 0.7 M for the sub-Neptune LP 791-18c and a mass of [Formula: see text] for the exo-Earth LP 791-18d. The gravitational interaction with the sub-Neptune prevents the complete circularization of LP 791-18d's orbit, resulting in continued tidal heating of LP 791-18d's interior and probably strong volcanic activity at the surface.

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http://dx.doi.org/10.1038/s41586-023-05934-8DOI Listing

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