Astronomers Edge Closer to Confirming Atmosphere on TRAPPIST-1 e
Astronomers are on the verge of potentially confirming an Earth-like atmosphere on the exoplanet TRAPPIST-1 e, based on preliminary observations made by the James Webb Space Telescope. This discovery could mark a significant milestone in the search for habitable worlds beyond our solar system. The TRAPPIST-1 system, located approximately 40 light-years from Earth, was first identified by Belgian astronomers in 2016. It consists of at least seven rocky planets orbiting a small star, which is about the size of Jupiter.
Néstor Espinoza, an astronomer at the Space Telescope Science Institute in Baltimore, noted the unique characteristics of the TRAPPIST-1 system. “As a planetary system, it’s as alien as it gets,” he remarked. Among these planets, three are situated within what is termed the habitable zone, suggesting they could potentially support liquid water if they possess atmospheres.
The recent study, published in The Astrophysical Journal Letters, focused on TRAPPIST-1 e, the fourth planet from its star. Four observations conducted with the Webb telescope in 2023 did not rule out the possibility of an atmosphere, leading to optimism among researchers. “Based on the first four observations, we cannot tell that (this planet) doesn’t have an atmosphere, so the dream is still alive,” Espinoza stated. He added that a follow-up program involving 15 additional observations is underway.
So far, the Webb telescope has only definitively ruled out an atmosphere on TRAPPIST-1 b, the innermost planet. The remaining six planets, including TRAPPIST-1 e, remain under scrutiny. Espinoza emphasized the significance of these observations, stating that they could provide insights into the potential for liquid surface water on TRAPPIST-1 e.
The planet’s orbit around its star is notably rapid, completing a full rotation every six days. This proximity to its star results in conditions that differ significantly from those of Earth. Espinoza explained that if the TRAPPIST-1 star were placed in our solar system, all its planets would fit within the orbit of Mercury.
To detect an atmosphere, astronomers observe a planet as it transits in front of its star, noting any slight changes in starlight. Such changes can indicate the presence of an atmosphere and help determine its chemical composition. The recent observations have ruled out a primary hydrogen-based atmosphere on TRAPPIST-1 e, suggesting it may have experienced significant radiation from its star, similar to early Earth.
A second study, also published in The Astrophysical Journal Letters, explores the possibility of TRAPPIST-1 e having an atmosphere rich in nitrogen, akin to that of Earth or Saturn’s moon Titan, rather than one dominated by carbon dioxide like those of Venus and Mars. Sara Seager, a professor of planetary science at the Massachusetts Institute of Technology and coauthor of both studies, remarked, “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.”
Espinoza’s team aims to complete the remaining observations by the end of the year, with two-thirds of the new round already finished. Should they find compelling evidence of an atmosphere, this could prompt even more extensive observations to detect specific chemical signatures, such as methane. The confirmation of an atmosphere would represent a significant leap forward in understanding whether red dwarf systems can sustain such conditions.
Michaël Gillon, research director at Belgium’s University of Liège and the original discoverer of the TRAPPIST-1 system, expressed enthusiasm regarding the Webb results. “The data are not yet conclusive,” he noted, “but they prove that JWST has the power to detect an Earth-like atmosphere if it exists. For the first time in history, we are truly within reach of discovering an atmosphere around a potentially habitable rocky exoplanet.”
The planets in the TRAPPIST-1 system exhibit a range of conditions reminiscent of terrestrial planets in our solar system. These conditions suggest the potential for liquid water on their surfaces, provided they possess adequate atmospheres to prevent water from freezing or escaping into space. Eric Agol, an astronomy professor at the University of Washington, highlighted TRAPPIST-1 e as the most promising candidate for an Earth-like atmosphere among the seven planets.
Howard Chen, an assistant professor of space sciences at the Florida Institute of Technology, described TRAPPIST-1 e as being at a “tipping point” based on simulations he has conducted. He indicated that the planet could evolve into either a dry desert 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,” Chen remarked.
The ongoing research into TRAPPIST-1 e represents a pivotal moment in the quest to understand the potential for life beyond Earth. With the capabilities of the James Webb Space Telescope, astronomers are optimistic that they may soon uncover vital information about the atmosphere of this intriguing exoplanet.
