ASTRONOMERS may be on the verge of a historic discovery – confirmation of an Earth-like atmosphere on a distant exoplanet. Preliminary observations from the James Webb Space Telescope are promising, but more detailed analyses are now awaited. The planet in question is TRAPPIST-1 e, a rocky, Earth-sized world 40 light-years away that could have conditions for liquid water, writes CNN .
The unique TRAPPIST-1 system
The planet is part of the TRAPPIST-1 system, discovered in 2016. The system, named after the favorite beer of the Belgian astronomers who discovered it, has been under constant scrutiny by scientists ever since. “As a planetary system, it’s the most unusual thing you can imagine,” said Néstor Espinoza, an astronomer at the Space Telescope Science Institute in Baltimore. “The star is very, very small – about the size of Jupiter – and there are at least seven rocky planets orbiting it. Three of them are in what we call the habitable zone, which means they are close enough to the star that, if they had an atmosphere, they could support liquid water.”
Espinoza and his colleagues focused on TRAPPIST-1 e, the fourth planet from the star, in a study published last week in The Astrophysical Journal Letters. Four observations conducted in 2023 with the Webb telescope failed to rule out the presence of an atmosphere, which prompted optimism. “Based on the first four observations, we can’t say that [this planet] doesn’t have an atmosphere, so the dream is still alive — it could still have an atmosphere,” Espinoza said, “and that’s super exciting, because we have a program of 15 more observations.”
Search for key characters
When looking for an atmosphere, astronomers wait for a planet to pass in front of its star and record changes in the light that filters through it. In this way, they look for chemical clues that reveal the composition of the atmosphere. Four observations so far have ruled out the existence of a primary hydrogen-based atmosphere, which was probably blown away by the star’s radiation. A similar thing happened to Earth, which later developed a secondary atmosphere, and scientists hope that the same is true for the planet TRAPPIST-1 e.
Another study, also published last week, suggests that the planet likely doesn’t have a thick, carbon-dioxide-rich atmosphere like Venus or Mars, but instead suggests a nitrogen-rich one more similar to Earth. “TRAPPIST-1e remains one of our most compelling habitable zone planets, and these new results bring us one step closer to understanding what this world is like,” said Sara Seager, a professor of planetary science at MIT and co-author of both studies.
The James Webb Telescope Revolution
“Three years ago, before the launch of James Webb, these kinds of studies were science fiction,” Espinoza said. “Now I’m pretty confident that we’ll be able to see what kind of atmosphere TRAPPIST-1 e might have—and if it has an Earth-like atmosphere, we’ll be able to tell.” His team plans to complete another round of 15 observations by the end of the year. If they find solid evidence of an atmosphere, further studies will follow, looking for gases like methane, which is associated with life on Earth.
Confirmation of an atmosphere would be revolutionary because red dwarfs, like the star TRAPPIST-1, make up the majority of stars in the universe. “If it can happen there, it can happen anywhere. The opportunities for life just multiply,” Espinoza explained. Even if it turns out that there is no atmosphere, the result would be significant because it would make life on Earth even more special.
Exciting but incomplete results
Michaël Gillon, who led the team that discovered the TRAPPIST-1 system, finds these first results extremely exciting. “The data are not yet conclusive,” he added, “but they demonstrate that JWST has the power to detect an Earth-like atmosphere if one exists. For the first time in history, we are truly within reach of detecting an atmosphere around a potentially habitable rocky exoplanet.”
Scientists agree that the results are intriguing, but incomplete. Howard Chen of the Florida Institute of Technology says the planet is at a “tipping point” – it could have evolved as an extremely dry or a water-rich world. “The fact that TRAPPIST-1e can be either very dry or very wet means that the next few observations by JWST could yield a dramatic discovery,” Chen said.
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