TRAPPIST 1 flares mapped to probe planetary habitability

by Robert Schreiber
Boulder CO (SPX) Dec 05, 2025

TRAPPIST-1, a small star about 40 light-years from Earth in the constellation Aquarius, produces flares roughly six times per day, and this activity complicates efforts to evaluate whether its planets could be habitable.

A team led by the University of Colorado Boulder used NASAs James Webb Space Telescope together with detailed computer simulations to study how these flares arise and how they might influence the systems seven Earth-sized planets, including three that orbit in the habitable zone where surface liquid water is possible.

The researchers analyzed Webb observations of six TRAPPIST-1 flares recorded in 2022 and 2023 and applied a new grid of flare-physics models developed by co-author Adam Kowalski to reconstruct the underlying magnetic processes driving the events.

These models describe how twisted magnetic fields in the star store energy and then release it through reconnection, launching beams of electrons through the stellar atmosphere that heat plasma and generate radiation across infrared, visible, ultraviolet, and X-ray wavelengths.

Lead author and NASA Sagan Fellow Ward Howard explained that the team suspects the innermost TRAPPIST-1 planets no longer have atmospheres and now resemble bare rocky bodies after long-term exposure to this flare activity.

TRAPPIST-1 has less than 10 percent of the Suns mass and is only slightly larger than Jupiter, yet it hosts seven terrestrial planets, three in the habitable zone, but frequent flares have made it difficult for astronomers to obtain clean transit spectra of these worlds.

Howard noted that when astronomers began observing TRAPPIST-1, they did not anticipate that many planetary transit observations would be obstructed by large flares, forcing researchers to develop methods to correct for stellar activity in their data.

Webb measures each flare in infrared light, but by pairing those observations with flare models, scientists can infer the properties of the initiating electron beams and effectively work backward to estimate the physical conditions that triggered each event.

The team found that TRAPPIST-1s flares are weaker than expected for a star of this type, with electron beams about ten times less energetic than those typically producing flares on similar low-mass stars, leading Howard to describe them as relatively wimpy.

Because the same electron beams that generate the infrared emission also produce ultraviolet and X-ray radiation, the modeling will help quantify the full radiation environment around the planets and assess how repeated flares may alter atmospheric chemistry over time.

Scientists are particularly interested in TRAPPIST-1e, a planet in the habitable zone that may show hints of an atmosphere with similarities to Earths, making it a key target for future observations of potential habitability.

Howard said that by simulating flares in detail, researchers can estimate how each event changes the radiation environment at the orbits of individual planets and refine expectations for whether these worlds can retain atmospheres.

The study, published in The Astrophysical Journal Letters on November 20, includes co-authors from the University of Chicago, Johns Hopkins University, Max Planck Institute for Solar System Research, Massachusetts Institute of Technology, the University of Oxford, and Universite de Montreal.

Research Report:TRAPPIST-1's Weak Flares and Implications for Habitability in the TRAPPIST-1 System