An intriguing discovery has emerged from the TRAPPIST-1 system, located just 40 light years from Earth. Astronomers using the James Webb Space Telescope (JWST) have detected indications that the Earth-sized exoplanet TRAPPIST-1e may possess a life-supporting atmosphere. This finding fuels hopes in the quest for potentially habitable worlds beyond our Solar System.
The observations reveal hints of a gaseous envelope around TRAPPIST-1e that resembles Earth’s atmosphere, suggesting the possibility of liquid water on its surface. While the detection remains ambiguous and requires extensive follow-up, it marks a significant step in identifying planets that could support life. Sara Seager, an astronomer at the Massachusetts Institute of Technology (MIT) and co-author of one of the papers detailing these findings, stated, “TRAPPIST-1e remains one of our most compelling habitable-zone planets, and these new results take us a step closer to knowing what kind of world it is.”
The search for habitable planets often hinges on the presence of liquid water, a vital component for life as we know it. Scientists seek exoplanets situated within the habitable zone of their host stars—regions where temperatures allow for water to remain liquid. The TRAPPIST-1 system, discovered in 2016, consists of seven rocky exoplanets that fall within this crucial zone.
Yet, the existence of an atmosphere is equally critical for maintaining liquid water. Red dwarf stars, like the one in the TRAPPIST-1 system, are cooler and more active than stars like the Sun. This activity could potentially strip away planetary atmospheres. Notably, previous investigations of TRAPPIST-1d, another planet in the system’s habitable zone, revealed no signs of an atmosphere.
In contrast, TRAPPIST-1e is located at a slightly greater distance from the star, raising hopes for a stable atmosphere. A research team led by Néstor Espinoza from the Space Telescope Science Institute (STScI) and Natalie Allen from Johns Hopkins University conducted a study of starlight as TRAPPIST-1e transited in front of its host star. They focused on detecting changes in starlight that could indicate the composition of the atmosphere.
The analysis of the data, which included four transits, was challenging due to the need to account for potential contamination caused by the star’s activity. The findings, while not definitive, have generated excitement. Ryan MacDonald, an astrophysicist at the University of St Andrews in the UK, noted, “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. But our initial observations cannot yet rule out a bare rock with no atmosphere.”
If an atmosphere does exist, it may offer clues about its composition. As starlight passes through an atmosphere, certain wavelengths can be absorbed and re-emitted by the gases present. By analyzing the spectrum, scientists can identify the elements and molecules within it. Preliminary results suggest a low concentration of carbon dioxide, indicating that TRAPPIST-1e does not resemble the atmospheres of Venus or Mars. Instead, the spectrum aligns with an atmosphere rich in molecular nitrogen, alongside trace amounts of carbon dioxide and methane.
This finding is particularly compelling, as Earth’s atmosphere is approximately 78 percent molecular nitrogen. If validated, TRAPPIST-1e could be deemed the most Earth-like exoplanet discovered to date.
Despite the promising signs, researchers emphasize that further observations are necessary to confirm the presence of an atmosphere. Fortunately, additional JWST observations are planned, allowing scientists to gather more data to either validate or dismiss the existence of an atmosphere on TRAPPIST-1e.
Glidden expressed enthusiasm about the potential for future discoveries, stating, “We are really still in the early stages of learning what kind of amazing science we can do with Webb. It’s incredible 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.”
The research findings are published in two parts in The Astrophysical Journal Letters, contributing to the growing understanding of exoplanets and their potential habitability. As technology advances, the exploration of distant worlds continues to unfold, enhancing our understanding of the universe and our place within it.
