JWST Thermal Emission of the Terrestrial Exoplanet GJ 1132b

2024/08/23 by Qiao Xue, Jacob L. Bean, Michael Zhang +14 · 1 voice · 14 citations
Chemistry · Earth and Planetary Sciences · Physics and Astronomy · #High-pressure geophysics and materials #Spectroscopy and Laser Applications #Stellar, planetary, and galactic studies #astro-ph.EP

paper · pdf · doi:10.3847/2041-8213/ad72e9

arxiv published 2024/08/23 · arxiv updated 2024/08/23 · openalex publication_date 2024/09/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

Abstract We present thermal emission measurements of GJ 1132b spanning 5–12 μ m obtained with the Mid-Infrared Instrument Low-Resolution Spectrometer on the James Webb Space Telescope. GJ 1132b is an M dwarf rocky planet with T eq = 584 K and an orbital period of 1.6 days. We measure a white-light secondary eclipse depth of 140 ± 17 ppm, which corresponds to a dayside brightness temperature of T p ,dayside = 709 ± 31 K using improved star and planet parameters. This measured temperature is only 1 σ below the maximum possible dayside temperature of a bare rock (i.e., assuming a zero-albedo planet with no heat redistribution, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>max</mml:mi> </mml:mrow> </mml:msub> </mml:math> = <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>746</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>11</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>14</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> K). The emission spectrum is consistent with a featureless blackbody, which agrees with a wide range of possible surface compositions. By comparing forward models to the dayside emission spectrum, we rule out Earth-thickness ( P ∼ 1 bar) atmospheres with at least 1% H 2 O, atmospheres of any modeled thickness (10 −4 to 10 2 bars) that contain at least 1% CO 2 , and thick, Venus-like atmospheres ( P ≳ 100 bars) with at least 1 ppm CO 2 or H 2 O. We therefore conclude that GJ 1132b likely does not have a significant atmosphere. This finding supports the concept of a universal “cosmic shoreline” given the high level of bolometric and extreme ultraviolet (EUV) and X-rays (collectively XUV) irradiation received by the planet.

Citations

• batman: BAsic Transit Model cAlculatioN in Python
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• Spectroscopic Time Series Performance of the Mid-infrared Instrument on the JWST
• Double Trouble: Two Transits of the Super-Earth GJ 1132 b Observed with JWST NIRSpec G395H
• Using JWST Transits and Occultations to Determine ∼1% Stellar Radii and Temperatures of Low-mass Stars

Cited by

• Impact of Subsurface Temperature Gradients on Emission Spectra of Airless Exoplanets: the Solid-state Greenhouse and Anti-Greenhouse
• Mechanisms of Superrotation in Slowly-Rotating and Tidally-Locked Planets
• The Open-Source Photochem Code: A General Chemical and Climate Model for Interpreting (Exo)Planet Observations
• Possible Evidence for the Presence of Volatiles on the Warm Super-Earth TOI-270 b
• JWST-TST DREAMS: NIRSpec/PRISM Transmission Spectroscopy of the Habitable Zone Planet TRAPPIST-1 e
• Do Rocky Planets around M Stars Have Atmospheres? A Statistical Approach to the Cosmic Shoreline
• The 3D Cosmic Shoreline for Nurturing Planetary Atmospheres
• A first look at rocky exoplanets with JWST
• Four Sub-Earth Planets Orbiting Barnard’s Star from MAROON-X and ESPRESSO
• Highlights from Exoplanet Observations by the James Webb Space Telescope
• Retention of surface water on tidally locked rocky planets in the Venus zone around M dwarfs
• The Cosmic Shoreline Revisited: A Metric for Atmospheric Retention Informed by Hydrodynamic Escape
• Prospects for Detecting Signs of Life on Exoplanets in the JWST Era
• Exploration of Exoplanet Atmospheres with the James Webb Space Telescope

Discussions

• Yet another M dwarf hot rocky planet without an atmosphere... If this holds for their habitable zones, the red sky paradox is gone. [bsky, 4 points, 1 comments]

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