GJ 367b is a dark, hot, airless sub-Earth

Abstract

We present the mid-infrared (5-12 $\mu$m) phase curve of GJ 367b observed by the Mid-Infrared Instrument (MIRI) on the James Webb Space Telescope (JWST). GJ 367b is a hot (T_eq=1370 K), extremely dense (10.2 +- 1.3 g/cm^3) sub-Earth orbiting a M dwarf on a 0.32 d orbit. We measure an eclipse depth of 79 +- 4 ppm, a nightside planet-to-star flux ratio of 4 +- 8 ppm, and a relative phase amplitude of 0.97 +- 0.10 -- all fully consistent with a zero-albedo planet with no heat recirculation. Su ch a scenario is also consistent with the phase offset of 11 +- 5 degrees East to within 2.2$\sigma$. The emission spectrum is likewise consistent with a blackbody with no heat redistribution and a low albedo of A_B ~ 0.1, with the exception of one anomalous wavelength bin that we attribute to unexplained systematics. The emission spectrum puts few constraints on the surface composition, but rules out a CO2 atmosphere >~ 1 bar, an outgassed atmosphere >~10 mbar (under heavily reducing conditions), or an outgassed atmosphere >~0.01 mbar (under heavily oxidizing conditions). The lack of day-night heat recirculation implies that 1 bar atmospheres are ruled out for a wide range of compositions, while 0.1 bar atmospheres are consistent with the data. Taken together with the fact that most of the dayside should be molten, our JWST observations suggest the planet must have lost the vast majority of its initial inventory of volatiles.

Published by ApJL

References in corpus (20)

• The NumPy array: a structure for efficient numerical computation
• Kepler Flares I. Active and Inactive M dwarfs
• Thermal emission from the Earth-sized exoplanet TRAPPIST-1 b using JWST
• Inverting Phase Functions to Map Exoplanets
• A reflective, metal-rich atmosphere for GJ 1214b from its JWST phase curve
• High temperature condensate clouds in super-hot Jupiter atmospheres
• Self-luminous and irradiated exoplanetary atmospheres explored with HELIOS
• Theoretical Emission Spectra of Atmospheres of Hot Rocky Super-Earths
• GJ 367b: A dense ultra-short period sub-Earth planet transiting a nearby red dwarf star
• GJ 1252b: A Hot Terrestrial Super-Earth With No Atmosphere
• Survival of Terrestrial N2-O2 Atmospheres in Violent XUV Environments through Efficient Atomic Line Radiative Cooling
• Hot, rocky and warm, puffy super-Earths orbiting TOI-402 (HD 15337)
• The Detectability of Rocky Planet Surface and Atmosphere Composition with JWST: The Case of LHS 3844b
• JWST MIRI flight performance: Detector Effects and Data Reduction Algorithms
• Low Albedo Surfaces of Lava Worlds
• Company for the ultra-high density, ultra-short period sub-Earth GJ 367 b: discovery of two additional low-mass planets at 11.5 and 34 days
• Revisiting the Iconic Spitzer Phase Curve of 55 Cancri e: Hotter Dayside, Cooler Nightside and Smaller Phase Offset
• Forming super-Mercuries: The role of stellar abundances
• Narrow loophole for H2-dominated atmospheres on habitable rocky planets around M dwarfs
• A Distinct Population of Small Planets: Sub-Earths

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