In the quest to understand our place in the universe, few discoveries ignite as much wonder as the possibility of finding another Earth-like world. Thanks to the James Webb Space Telescope (JWST), astronomers are inching closer to glimpsing such a planet. University of Bristol astrophysicists, working alongside an international team, are helping to peel back the cosmic curtain on TRAPPIST-1e, a small planet about the size of Earth, orbiting a dim red dwarf star just 40 light years away.
What makes this world so tantalizing is the possibility that liquid water could exist on its surface—an essential ingredient for life as we know it. But that possibility rests on a crucial question: does TRAPPIST-1e have an atmosphere? The answer, for now, remains a mystery, though recent observations are offering the clearest hints yet.
The Promise of TRAPPIST-1e
Exoplanets—worlds orbiting stars beyond our own solar system—are as varied as the imagination can stretch. Gas giants larger than Jupiter, scorched rocky bodies, and frozen worlds far from their stars all populate the galaxy. But TRAPPIST-1e stands apart. It orbits in the so-called “habitable zone” of its star, the region where temperatures could, under the right conditions, allow water to remain liquid.
That condition depends on more than distance from the star. Without an atmosphere, any surface water would boil away or freeze solid. An atmosphere acts as both shield and blanket—protecting the planet from harmful radiation while trapping enough heat to stabilize conditions for liquid water. Whether TRAPPIST-1e possesses such an atmosphere is the central puzzle researchers are determined to solve.
JWST’s Gaze on a Distant World
The James Webb Space Telescope is humanity’s most powerful tool for studying distant planets. By watching as TRAPPIST-1e passes in front of its star, astronomers use JWST’s Near-Infrared Spectrograph (NIRSpec) to capture starlight filtering through the planet’s thin veil of gases. If an atmosphere exists, it leaves a fingerprint in the form of subtle dips in the star’s spectrum, revealing what molecules are present.
Already, four such transits have been observed. The first results, published in The Astrophysical Journal Letters, suggest several possible scenarios. There might be a secondary atmosphere—built up after the planet’s violent early years—or there might be nothing at all. The data refine earlier, less detailed measurements from the Hubble Space Telescope, nudging scientists closer to clarity but not yet providing definitive proof.
Dr. Hannah Wakeford, Associate Professor in Astrophysics at the University of Bristol and a leading figure in the project, described the moment with cautious excitement: “What we have found with JWST in these first four observations helps refine the earlier Hubble measurements and reveals there might now be hints of an atmosphere, but we cannot yet rule out the possibility there is nothing to detect.”
A Planet Without Its First Breath
One key revelation is what TRAPPIST-1e does not have. Early planets often form with a thick envelope of hydrogen and helium, remnants from the swirling disk of gas around their star. Earth itself once had such an atmosphere, but it was stripped away by solar winds and violent impacts, paving the way for the secondary, life-sustaining atmosphere we breathe today.
According to co-author Dr. David Grant, formerly at the University of Bristol, TRAPPIST-1e’s primordial hydrogen-based atmosphere is long gone. The culprit is likely its parent star. TRAPPIST-1, a small but active red dwarf, bombards its planets with flares and radiation strong enough to scour away lightweight gases. Whether TRAPPIST-1e managed to build a denser, protective atmosphere afterward remains the pivotal question.
Dr. Wakeford notes that Earth’s own story may provide a parallel: “Many planets, including Earth, build up a heavier secondary atmosphere after losing their primary atmosphere. It is possible planet e was never able to do this and doesn’t have a secondary atmosphere, but there’s an equal chance one does exist.”
The Role of a Greenhouse Effect
If TRAPPIST-1e has rebuilt its atmosphere, the gases it contains will determine whether water can remain stable on its surface. On Earth, carbon dioxide and other greenhouse gases keep our planet warm enough for life to flourish. Too much of this effect, as on Venus, creates a suffocating hothouse. Too little, as on Mars, leaves a frigid desert.
Theoretical models suggest TRAPPIST-1e is unlikely to be dominated by carbon dioxide like Venus, but modest amounts could create just enough warmth. If that is the case, liquid water might pool in a global ocean or gather in regions of perpetual daylight on the tidally locked planet, where one side always faces the star and the other remains in darkness. Around the edge of this twilight zone, seas and ice could coexist in a delicate balance.
As Dr. Ana Glidden of MIT, lead author of the theoretical study, explained: “It is unlikely the atmosphere of planet e is dominated by carbon dioxide, like the thick atmosphere of Venus and the thin atmosphere of Mars. But it’s also important to note there are no direct parallels with our solar system. TRAPPIST-1 is a very different star from our sun, and the planetary system around it is also distinct.”
Building Toward an Answer
The search for TRAPPIST-1e’s atmosphere is far from finished. Future JWST observations will add more transits, each sharpening the spectral fingerprints. Scientists also plan to compare planet e with its neighbors, including planet b, which orbits closer to the star. By contrasting multiple worlds in the same system, researchers can better disentangle what comes from the star and what comes from the planets themselves.
Dr. Néstor Espinoza of the Space Telescope Science Institute highlighted the promise ahead: “Webb’s infrared instruments are giving us more detail than we’ve ever had access to before, and the initial four observations we’ve been able to make of planet e are showing us what we will have to work with when the rest of the information comes in.”
Each new dataset is a step closer to resolving one of astronomy’s most profound questions: are there other Earths out there, worlds where seas stretch beneath alien skies, and perhaps, where life itself may stir?
A Global Effort to Understand the Cosmos
This work is part of the JWST-TST DREAMS program, led by Dr. Nikole Lewis at Cornell University, bringing together more than 30 scientists from across the world. The University of Bristol team is deeply embedded in this collaboration, building on their earlier groundbreaking work, such as the detection of exotic quartz clouds on another exoplanet.
The JWST itself represents the pinnacle of international cooperation—a joint mission by NASA, the European Space Agency, and the Canadian Space Agency. From its vantage point a million miles from Earth, it gazes across time and space, turning faint signals into revelations about distant worlds.
The Wonder of What Lies Ahead
As data continue to pour in, TRAPPIST-1e reminds us of the extraordinary moment we are living in. For the first time in history, humanity has the tools to probe the atmospheres of rocky planets orbiting other stars. Each new measurement brings us closer to answering whether Earth is unique—or whether the galaxy teems with ocean worlds and living skies.
Dr. Wakeford captured this spirit of discovery with quiet awe: “It’s incredibly exciting to be peeling back the curtain on these fascinating other worlds, measuring the details of starlight around Earth-sized planets to ascertain what it might be like, and if life could be possible.”
Forty light years may sound impossibly far, yet in cosmic terms, TRAPPIST-1e is a neighbor. Whether its surface holds an endless sea, frozen plains, or bare rock, the very act of studying it deepens our understanding of what is possible in the universe. And with each new discovery, we are reminded that we are explorers at heart, looking outward to find not just other worlds, but new reflections of ourselves.
