Astronomers are on the brink of a significant discovery regarding an Earth-like atmosphere on an exoplanet located in the TRAPPIST-1 system, approximately 40 light-years from Earth. Preliminary observations from the James Webb Space Telescope indicate that the planet, specifically TRAPPIST-1 e, may possess conditions suitable for liquid water, a key factor for potential habitability. These findings are part of a study published in The Astrophysical Journal Letters.
The TRAPPIST-1 system, discovered in 2016 by a team of Belgian astronomers, comprises at least seven rocky planets orbiting a small star roughly the size of Jupiter. According to Néstor Espinoza, an astronomer at the Space Telescope Science Institute in Baltimore, three of these planets reside in what is termed the habitable zone. This zone is characterized by proximity to the star that allows for the possibility of retaining liquid water if an atmosphere is present.
Optimism about TRAPPIST-1 e’s potential atmosphere stems from four observations conducted in 2023. While these observations did not rule out the existence of an atmosphere, they left the possibility open. Espinoza stated, “Based on the first four observations, we cannot tell that (this planet) doesn’t have an atmosphere, so the dream is still alive — it could still have an atmosphere.” This ongoing research includes a follow-up program with 15 additional observations planned to further investigate the planet’s atmospheric conditions.
TRAPPIST-1 e is particularly intriguing due to its Earth-like size and its rapid orbital period of just six days around its star. The compact nature of the TRAPPIST-1 system means that if the star were placed within our solar system, all the planets would fit within the orbit of Mercury. Astronomers employ a technique known as transit photometry, where they monitor changes in starlight as the planet moves in front of its star, to glean information about the planet’s atmosphere.
Recent data suggest that TRAPPIST-1 e is unlikely to possess a hydrogen-dominated atmosphere, which may have been stripped away by intense radiation from the host star. Instead, researchers are considering the possibility of a nitrogen-rich atmosphere, akin to that of Earth or Saturn’s moon Titan. Sara Seager, a professor of planetary science at the Massachusetts Institute of Technology, emphasized the significance of these findings, stating, “TRAPPIST-1 e 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 research team aims to complete the new round of observations by the end of 2023, with two-thirds already finished. Should they discover clear signs of an atmosphere, further observations might be necessary to identify specific chemical signatures, such as methane, which is often associated with biological activity on Earth. “It would settle a huge debate going on right now on whether these red dwarf systems can sustain an atmosphere or not,” Espinoza noted. “If it can happen there, it can happen anywhere. The possibilities for life just kind of multiply.”
While the potential discovery of an atmosphere is thrilling, Espinoza acknowledged that even if it were ruled out, it would enhance the understanding of life’s uniqueness on Earth. This outcome would also pave the way for future explorations of exoplanets revolving around yellow dwarf stars like our sun, using even more advanced telescopes that are currently in development.
The implications of this research extend beyond just TRAPPIST-1 e. According to Michaël Gillon, the research director of the Astrobiology Research Unit at University of Liège, the initial findings are promising but not conclusive. He remarked, “For the first time in history, we are truly within reach of discovering an atmosphere around a potentially habitable rocky exoplanet.”
The TRAPPIST-1 planets mirror the conditions of terrestrial planets in our own solar system, making them viable candidates for harboring surface liquid water. An atmosphere is essential to prevent water from freezing or escaping into space, as explained by Eric Agol, an astronomy professor at the University of Washington. He emphasized that TRAPPIST-1 e stands out among its seven planetary companions as a leading candidate for an Earth-like atmosphere.
Additionally, Howard Chen, an assistant professor of space sciences at the Florida Institute of Technology, described TRAPPIST-1 e as existing at a “tipping point.” Based on computer simulations, the planet could either emerge as a dry, barren world or a water-rich environment. “The fact that TRAPPIST-1 e can plausibly be either very dry or very wet means the next few JWST observations could deliver a dramatic reveal,” he stated.
As the scientific community eagerly awaits the results of the ongoing observations, the potential for groundbreaking discoveries about TRAPPIST-1 e and other exoplanets continues to inspire both researchers and the public alike.