GJ 1132 b Likely Lacks an Atmosphere, New JWST Data Confirms
Recent research utilizing data from the James Webb Space Telescope (JWST) strongly suggests that the exoplanet GJ 1132 b does not possess an atmosphere. The study, published in the Astronomy Journal (Patalha & Hassa, 2025, DOI: 10.3847/1538-3881/ADF198), resolves conflicting earlier observations from JWST regarding the planet’s atmospheric composition.
Initial JWST observations of GJ 1132 b,during planetary transits,yielded inconsistent results. One transit appeared to indicate an atmosphere rich in water, while another showed no evidence of an atmosphere at all.Researchers analyzed data from two additional transits and found compelling evidence supporting the conclusion that GJ 1132 b is likely airless.
While a very thin “steam” atmosphere (approximately 1 mbar) cannot be entirely ruled out by the data, astronomers consider this unlikely given the planet’s close proximity to its star and the scarcity of water. Crucially, the possibility of even this thin atmosphere diminishes significantly when the initial dataset suggesting a water-rich atmosphere is excluded from the analysis – meaning all four datasets analyzed now align in indicating a lack of atmosphere.
The discrepancy in the initial data was traced back to variations on the surface of GJ 1132 b’s host star. The star exhibited more “cool spots” during the first transit observation, influencing the data collected about the planet. Researchers believe these stellar features created the illusion of an atmosphere where none exists. The authors recommend employing a “Leave-One-Out” approach when analyzing exoplanet datasets, especially when observing stars with notable surface variations.
The study also examined the effectiveness of different JWST instrumentation modes. Data was collected using both the high-resolution G395H and medium-resolution G395M modes of the NIRSSPEC instrument. While G395H has a data gap between 3.75µm and 3.82µm, the authors found comparable noise levels between the two modes. They suggest using medium resolution for single transit observations, but high resolution is viable with multiple observations.
This research effectively refutes the earlier hypothesis that GJ 1132 b has a substantial atmosphere. Furthermore, it provides a methodological advice to avoid similar confusion in future exoplanet atmosphere studies. The findings contribute to the ongoing debate about the atmospheric survivability of planets orbiting M-dwarf stars, and appear to support the idea that these planets struggle to retain atmospheres.
(Credit: NASA/JPL-Caltech/robert Hurt)
https://www.youtube.com/watch?v=dhho0npdhz8 – Fraser discusses the exoplanet atmosphere with Dr.Joanna Barstow
Adapted from an article originally published in Universe Today.
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