Free Astronomy Magazine November-December 2025

NOVEMBER-DECEMBER 2025 However many planets, in- cluding Earth, build up a heavier secondary atmos- phere after losing their pri- mary atmosphere. It is possible that planet e was never able to do this and does not have a secondary atmos- phere. Yet researchers say there is an equal chance there is an atmos- phere, and the team developed novel approaches to working with Webb’s data to determine planet e’s potential atmospheres and surface environments. The researchers say it is unlikely that the atmosphere of TRAPPIST-1 e is dominated by car- bon dioxide, analogous to the thick atmosphere of Venus and the thin atmosphere of Mars. However, the researchers also are careful to note that there are no direct parallels with our solar system. “TRAPPIST-1 is a very different star from our Sun, and so the planetary system around it is also very different, which chal- lenges both our observational and theoretical assumptions,” said team member Nikole Lewis, an associate professor of astronomy at Cornell University. If there is liquid water on TRAPPIST-1 e, the researchers say it would be accompanied by a green- house effect, in which various gases, particularly carbon dioxide, keep the atmosphere stable and the planet warm. “A little greenhouse effect goes a long way,” said Lewis, and the measurements do not rule out adequate carbon dioxide to sus- tain some water on the surface. Ac- cording to the team’s analysis, the water could take the form of a global ocean, or cover a smaller area of the planet where the star is at perpetual noon, surrounded by ice. This would be possible because, due to the TRAPPIST-1 planets’ sizes and close orbits to their star, it is thought that they all are tidally locked, with one side always facing the star and one side always in dark- ness. Espinoza and co-principal in- vestigator Natalie Allen of Johns Hopkins University are leading a team that is currently making 15 ad- ditional observations of planet e, with an innovative twist. The scientists are timing the obser- vations so that Webb catches both planets b and e transiting the star one right after the other. After previous Webb obser- vations of planet b, the planet orbiting closest to TRAPPIST-1, scientists are fairly confident it is a bare rock without an atmosphere. This means that signals detected during planet b’s transit can be at- tributed to the star only, and be- cause planet e transits at nearly the same time, there will be less compli- cation from the star’s variability. Scientists plan to compare the data from both planets, and any indica- tions of chemicals that show up only in planet e’s spectrum can be attrib- uted to its atmosphere. “We are re- ally still in the early stages of learning what kind of amazing sci- ence we can do with Webb. It’s in- credible to measure the details of starlight around Earth-sized planets 40 light-years away and learn what it might be like there, if life could be possible there,” said Ana Glid- den, a post-doctoral researcher at Massachusetts Institute of Technol- ogy’s Kavli Institute for Astrophysics and Space Research, who led the re- search on possible atmospheres for planet e. “We’re in a new age of ex- ploration that’s very exciting to be a part of,” she said. T his graphic compares data collected by Webb’s NIR- Spec (Near-Infrared Spectrograph) with computer models of exoplanet TRAPPIST-1 e with (blue) and with- out (orange) an atmosphere. Narrow colored bands show the most likely locations of data points for each model. [NASA, ESA, CSA, STScI, Joseph Olmsted (STScI)] !