Key points
- James Webb Space Telescope (JWST) data definitively show GJ 1132 b, an exoplanet 41 light-years away, likely lacks an atmosphere.
- Conflicting previous data resulted from stellar activity (cool spots) on the host star, influencing observations.
- The study recommends a “leave-one-out” approach for analyzing exoplanet datasets to avoid similar inconsistencies.
- JWST’s NIRSpec instrument was used in two modes (G395H and G395M), providing valuable insights into data acquisition strategies.
New observations from the James Webb Space Telescope (JWST) have resolved a long-standing debate about the atmosphere of exoplanet GJ 1132 b. Located approximately 41 light-years from Earth, GJ 1132 b is a rocky planet slightly larger than Earth, orbiting its M-dwarf star at a remarkably close distance.
This proximity has led to conflicting data in previous studies, with some suggesting the presence of a water-rich atmosphere and others indicating the absence of an atmosphere altogether.
A new paper, published on the arXiv preprint server, utilizes additional JWST observational data to address this discrepancy. By analyzing two additional transits of GJ 1132b, the researchers found that the planet most likely lacks a substantial atmosphere.
While the possibility of a very low-pressure “steam” atmosphere remains, it’s considered improbable given the planet’s proximity to its star and the absence of detected water, previously observed in other JWST studies. Crucially, this conclusion is supported by three independent datasets, which consistently indicate the absence of an atmosphere.
The source of the conflicting initial data was identified as increased stellar activity on the host star. More “cool spots” were observed on the star’s surface during the initial transit, introducing biases into the planetary observations and creating the illusion of an atmosphere.
This highlights the importance of accounting for stellar variability in exoplanet atmospheric studies. The researchers suggest a “leave-one-out” data analysis approach, where each dataset is analyzed separately, to identify and mitigate such inconsistencies in future studies.
The study also provides valuable insights into JWST data acquisition strategies. The researchers utilized two modes of the JWST’s NIRSpec instrument (G395H and G395M) to compare high-resolution and medium-resolution data.
While the high-resolution mode had a small data gap, the authors found this did not significantly impact the results. They recommend using the medium-resolution mode for single transit observations to avoid lengthy observation times, but advocate for the high-resolution mode when multiple transits are possible.
This study significantly advances our understanding of exoplanet atmospheres, particularly those around M-dwarf stars, providing valuable lessons for future research.
