It is similar in size to Earth and completes a full orbit around its star in just six days. Scientists believe that the atmosphere of TRAPPIST-1e may be nitrogen-rich, similar to that of Earth or Titan
The exoplanet TRAPPIST-1e (whose name directly references the famous Belgian Trappist beer) lies about 40 light-years from Earth and has drawn the attention of the scientific community. Early observations from the James Webb Space Telescope suggest the possibility of an atmosphere.
The TRAPPIST-1 system, discovered in 2016 by Belgian astronomers, contains seven rocky planets orbiting a red dwarf star, three of which are located in the so-called habitable zone.
Scientists have focused on TRAPPIST-1e, the fourth planet from its star, and published their initial results in The Astrophysical Journal Letters. Four observations made in 2023 did not rule out the existence of an atmosphere, strengthening optimism that one may indeed exist. "The dream is alive. It may have an atmosphere," said astronomer Néstor Espinoza, adding that another 15 observations are already scheduled.
So far, the James Webb telescope has only ruled out the presence of an atmosphere on TRAPPIST-1b, the innermost planet. As for TRAPPIST-1e, early evidence excludes a primordial hydrogen-based atmosphere, and it also seems unlikely that it has a carbon-dioxide-rich atmosphere like Venus or Mars.
Instead, scientists estimate that TRAPPIST-1e's atmosphere is likely nitrogen-rich, resembling that of Earth or Titan.
TRAPPIST-1e is roughly Earth-sized and completes an orbit around its star every six days. Because the host star is so small, all seven planets orbit very close to it -- so close, in fact, that if placed in our Solar System, they would all fit within Mercury's orbit.
The studies are based on observing the dimming of the star's light as the planet passes in front of it. Subtle changes in the light that reaches the telescope reveal clues about the composition of the planet's atmosphere. Scientists hope that future observations may detect specific gases such as methane, which on Earth is linked to biological activity.
"Confirming such an atmosphere would be revolutionary," said Espinoza. "It would resolve the debate on whether planets around red dwarfs can retain atmospheres. If they can, then the possibilities for life in the universe multiply."
Professor Sara Seager of MIT emphasized that the data rule out Venus- or Mars-type atmospheres, leaving more Earth-like scenarios on the table. The new series of observations is expected to be completed by the end of the year, with potential follow-up studies afterward.
Even if no atmosphere is ultimately found, scientists stress that the results would still be significant, providing new insights into planetary habitability and paving the way for future, more powerful telescopes.