In hopeful news for the search for extraterrestrial life, University of St Andrews researchers have discovered signs suggesting a possible atmosphere surrounding the Earth-like exoplanet TRAPPIST-1e, located 40 million light-years away.
The discovery indicates that the planet may be habitable, as it is also covered in liquid surface water, either as an ocean or ice. Two new papers published in the Astrophysical Journal Letters reveal the new findings, made possible through data from the James Webb Space Telescope.
James Webb Observations
Working with international collaborators, University of St Andrews researchers performed the first search for an atmosphere on TRAPPIST-1e using the James Webb Space Telescope. The earth-like planet sits in the habitable zone of its red dwarf host star Trappist-1, meaning that it maintains an orbit near enough to melt ice, yet far enough that the water does not boil away. However, even sitting inside this “goldilocks” zone, an atmosphere is required for the planet to be a viable candidate for life.
The first data is not conclusive that TRAPPIST-1e contains an atmosphere, but that is one of the potential scenarios scientists suspect from this initial investigation, an important finding in the search for ET.
“TRAPPIST-1e has long been considered one of the best habitable zone planets to search for an atmosphere,” said Dr Ryan MacDonald, Lecturer in Extrasolar Planets in the School of Physics and Astronomy at the University of St Andrews. “But when our observations came down in 2023, we quickly realised that the system’s red dwarf star was contaminating our data in ways that made the search for an atmosphere extremely challenging.”
Exoplanet Spectrography
The team behind the potential atmospheric discovery rooted their research in spectrography, a process where light waves are separated and analyzed, often to determine an exoplanet’s atmospheric contents. To collect their spectrographic data, the researchers utilized the James Webb Space Telescope’s Near-Infrared Spectrograph (NIRSpec), as the target planet passed in front of its host star. Changes in the light coming from TRAPPIST-1 as the planet came between it and NIRSpec would provide information on the chemicals present on TRAPPIST-1e if it had an atmosphere.
To minimize the chances of a false positive, the team accounted for other explanations for any potential readings, such as spots that develop on a star’s surface through magnetic field interference, called star spots, which may coincidentally create alterations in the light that do not correspond to the planet’s passing. In total, the researchers corrected the data for more than a year to isolate the suspected atmospheric data.
“We are seeing two possible explanations. The most exciting possibility is that TRAPPIST-1e could have a so-called secondary atmosphere containing heavy gases like nitrogen,” Dr MacDonald said. “But our initial observations cannot yet rule out a bare rock with no atmosphere.”
Continuing the Hunt for a Habitable World
The search for TRAPPIST-1e’s atmosphere continues through further use of the James Webb Space Telescope. As scientists continue to peer at the exoplanet, each transit in front of its red dwarf host provides a more detailed understanding of the planet’s possible atmosphere.
“In the coming years, we will go from four JWST observations of TRAPPIST-1e to nearly twenty,” said Dr Macdonald. We finally have the telescope and tools to search for habitable conditions in other star systems, which makes today one of the most exciting times for astronomy.”
The papers, “JWST-TST DREAMS: NIRSpec/PRISM Transmission Spectroscopy of the Habitable Zone Planet TRAPPIST-1e” and “JWST-TST DREAMS: Secondary Atmosphere Constraints for the Habitable Zone Planet TRAPPIST-1e,” appeared in The Astrophysical Journal Letters on September 8, 2025.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.