TRAPPIST-1e
TRAPPIST-1e — A Potentially Habitable World
Located approximately 40 light-years from Earth in the constellation Aquarius, TRAPPIST-1e is a rocky, Earth-sized exoplanet orbiting an ultracool red dwarf star. It is one of seven known planets in the TRAPPIST-1 system and is considered a particularly promising candidate in the search for potentially habitable worlds beyond our Solar System.
The planet orbits within its star's habitable zone, where liquid water could exist under suitable atmospheric conditions. However, scientists have not confirmed whether TRAPPIST-1e possesses an atmosphere, surface water or conditions capable of supporting life. Ongoing observations, particularly with the James Webb Space Telescope, aim to investigate these possibilities.
The TRAPPIST-1 Planetary System
TRAPPIST-1 is an ultracool red dwarf star approximately 40 light-years from Earth, with just 9% of the Sun's mass. Seven Earth-sized planets orbit this small, faint star, all closer to it than Mercury is to the Sun.
🔍 Click image to enlarge
Despite their close proximity, several receive levels of stellar radiation that could permit liquid water under suitable atmospheric conditions.
The planets form an unusually compact system connected by gravitational interactions and orbital resonances. Three planets, TRAPPIST-1e, f and g, are commonly identified as lying within the star's habitable zone, although their actual habitability remains unknown. Studying these neighbouring rocky worlds helps astronomers understand planetary formation, atmospheric evolution and the conditions that might support life.
The TRAPPIST-1 Planetary System (artist's impression).
The Discovery of TRAPPIST-1e
The TRAPPIST-1 planetary system was first identified in 2016 by an international team led by Belgian astronomer Michaël Gillon at the University of Liège. Using the TRAPPIST-South telescope at the European Southern Observatory's La Silla Observatory in Chile, researchers detected planets by observing small reductions in starlight as they passed in front of their parent star.
Further observations, including those from NASA's Spitzer Space Telescope, revealed a total of seven Earth-sized planets, announced in February 2017. TRAPPIST-1e emerged as a particularly interesting world because of its rocky composition, Earth-like dimensions and position within the star's habitable zone. The discovery became a major milestone in the search for potentially habitable planets beyond our Solar System.
Size, Mass and Physical Characteristics
TRAPPIST-1e is a rocky exoplanet with a radius approximately 92% that of Earth and a mass around 69% of Earth's. Its estimated surface gravity is approximately 82% of Earth's, while its average density suggests a predominantly rocky interior, potentially consisting of an iron-rich core surrounded by a silicate mantle.
Although its physical characteristics resemble Earth's, scientists have not directly observed its surface or internal structure. Whether TRAPPIST-1e possesses mountains, oceans, volcanoes, active geology or a magnetic field remains unknown. Its Earth-like dimensions make it an important candidate for investigating how rocky planets develop beyond our Solar System.
Orbit and Tidal Locking
TRAPPIST-1e completes one orbit around its parent star every 6.1 Earth days, at a distance of approximately 4.4 million kilometres. Despite being much closer to its star than Earth is to the Sun, it receives only around two-thirds of Earth's incoming stellar energy because TRAPPIST-1 is considerably smaller and cooler than our Sun.
The planet is expected to be tidally locked, meaning one hemisphere may experience permanent daylight while the opposite remains in darkness. The boundary between these regions is called the terminator. If TRAPPIST-1e possesses a substantial atmosphere, winds could redistribute heat between the hemispheres, potentially allowing more moderate temperatures and conditions suitable for liquid water. Its actual rotation and climate remain unconfirmed.
Atmosphere and Climate
Whether TRAPPIST-1e possesses an atmosphere remains one of the most important unanswered questions about the planet. Observations by the James Webb Space Telescope, including research published in September 2025, have ruled out some atmospheric possibilities but have not confirmed an atmosphere. A substantial atmosphere containing heavier gases, potentially including nitrogen, remains possible, although an airless environment cannot yet be excluded.
If an atmosphere exists, it could transport heat between the planet's permanently illuminated and dark hemispheres, helping regulate surface temperatures. Greenhouse gases, clouds and atmospheric circulation could potentially create conditions suitable for liquid water.
Water, Oceans and Ice
Artist's impression.
TRAPPIST-1e orbits within its star's habitable zone, where suitable atmospheric conditions could allow liquid water to exist on the surface. Climate simulations suggest that, if the planet possesses sufficient atmospheric pressure and water, oceans could potentially remain liquid on parts of its illuminated hemisphere. However, no water, oceans or surface ice have been confirmed on TRAPPIST-1e.
If the planet is tidally locked, its permanently dark hemisphere could experience extremely low temperatures, potentially allowing extensive ice formation. Atmospheric circulation and ocean currents might redistribute heat, while internal geological energy could theoretically support water beneath an icy surface. These possibilities depend on environmental conditions that remain unknown, making the presence and distribution of water an important subject of ongoing research.
The Search for Life
TRAPPIST-1e is an important target in the search for extraterrestrial life because of its rocky composition, Earth-like size and position within its star's habitable zone. Scientists are particularly interested in whether it possesses liquid water, a stable atmosphere and the chemical ingredients necessary for biological activity. However, no evidence of life has been detected on TRAPPIST-1e, and its actual habitability remains unknown.
Astronomers investigate potential biosignatures, including atmospheric gases such as oxygen and methane that can be associated with biological processes. However, these gases can also form through non-biological reactions, making their interpretation challenging. Future observations may help determine whether TRAPPIST-1e has an atmosphere and whether its chemistry is compatible with habitability, although establishing convincing evidence of life would require much stronger scientific evidence.
The James Webb Space Telescope
The James Webb Space Telescope (JWST), developed through cooperation between NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA), is helping astronomers investigate TRAPPIST-1e from approximately 40 light-years away. Using infrared spectroscopy, scientists analyse subtle changes in starlight as the planet passes in front of its star, searching for evidence of atmospheric gases and investigating the planet's environmental conditions.
Observations published in 2025 provided important constraints on possible atmospheric compositions but did not confirm whether TRAPPIST-1e possesses an atmosphere. One major challenge is distinguishing potential atmospheric signals from interference caused by the star's magnetic activity. Continued Webb observations and improved analytical techniques could help determine whether the planet has retained an atmosphere capable of supporting conditions suitable for liquid water.
European Contributions to TRAPPIST-1 Research
European astronomers played a leading role in discovering the TRAPPIST-1 planetary system. The initial discovery in 2016 was led by Belgian astronomer Michaël Gillon and researchers at the University of Liège, using the TRAPPIST-South telescope at the European Southern Observatory's La Silla site in Chile. Further international observations established the existence of seven Earth-sized planets, announced in February 2017.
The European Space Agency (ESA) also contributes to the continuing investigation of TRAPPIST-1e through the James Webb Space Telescope, including its Near-Infrared Spectrograph (NIRSpec). European researchers are helping analyse planetary atmospheres, orbital dynamics and potential habitability. Future ESA missions, including PLATO and Ariel, will expand our understanding of exoplanets and their atmospheres, although neither is specifically designed to investigate TRAPPIST-1e.
The Future of TRAPPIST-1e Research
Future investigations of TRAPPIST-1e will focus on determining whether the planet possesses a substantial atmosphere and whether its environmental conditions could support liquid water. Continued observations with the James Webb Space Telescope will help astronomers investigate possible atmospheric gases, refine climate models and distinguish planetary signals from interference caused by the host star. These findings could significantly improve our understanding of rocky planets orbiting red dwarf stars.
Europe's future exoplanet missions, including ESA's PLATO and Ariel, will contribute to the wider search for potentially habitable worlds by studying planetary systems and atmospheric compositions. Although neither mission is specifically designed to characterise TRAPPIST-1e, their discoveries will provide valuable comparisons. Direct spacecraft exploration remains beyond current capabilities, but advances in astronomy may eventually reveal whether TRAPPIST-1e possesses environments capable of supporting life.
Latest Updates
13th October 2026 — James Webb Investigations of TRAPPIST-1e
Research published in September 2025 provided important new insights into the possible atmosphere of TRAPPIST-1e. Observations from the James Webb Space Telescope helped rule out certain atmospheric models but could not establish whether the planet possesses a substantial atmosphere. A heavier atmosphere remains possible, although an airless environment has not been excluded.
Scientists are continuing to investigate how activity on the planet's red dwarf star affects atmospheric measurements. Further observations and improved analysis could help determine whether TRAPPIST-1e has retained an atmosphere and whether conditions suitable for liquid water might exist.
Last reviewed: 13th October 2026