The James Webb space telescope has confirmed the first direct detection of water ice clouds on a giant exoplanet. The target is Epsilon Indi Ab, a super-Jupiter located just 12 light-years from Terra in the constellation Indus. The discovery was announced on April 22, 2026 by Max Planck Institute for Astronomy (MPIA) and represents a historic milestone for planetary astronomy.
An international team led by Elisabeth Matthews used JWST’s MIRI instrument with coronagraph to conduct the study. The results were published in Astrophysical Journal Letters. The detection of water ice clouds had been theorized for decades, but had never been directly observed until this investigation.
Como o James Webb identified the ice clouds
JWST employed the MIRI instrument (Mid-Infrared Instrument) equipped with a coronagraph. Essa configuration blocks light from the host star Epsilon Indi A, directly revealing the faint light reflected and emitted by the planet. The technique used is called “direct imaging”, different from in-transit spectroscopy, which only detects indirect effects.
The collected spectrum presented spectral lines incompatible with atmospheric models that did not include clouds. Conforme observed by the team expected ammonia or methane molecules, but the data revealed frozen water in the coldest regions of the upper atmosphere. The presence of water in the form of ice, and not steam, confirms temperatures close to 275 Kelvin, equivalent to around 2 °C.
Ice clouds inhabit Epsilon Indi Ab’s upper atmosphere at altitudes where freezing is possible. Esse discovery expands the catalog of known atmospheric processes on giant planets. Antes From this observation, clouds had only been detected on Sistema Solar planets: Júpiter, Saturno, Urano and Netuno.
Características that made Epsilon Indi Ab observable
Epsilon Indi A is a K-type star, known as an orange dwarf. Epsilon Indi Ab is the third closest star system to Terra, behind only Alpha Centauri and Barnard’s Star. The large orbital distance of 30 astronomical units allows the planet to orbit far enough from the starlight for the coronagraph to be able to separate its brightness without total interference.
The planet’s low temperature makes it visible mainly in the mid-infrared, the spectral range where MIRI has greater sensitivity. The 180-year orbital period means this exoplanet has never been seen to complete a single transit in front of the star. For this reason, direct imaging is the only viable methodology for its study, a technique that JWST has drastically improved compared to the Hubble telescope.
The orbital and atmospheric data converge on a coherent scenario: a giant planet far from the star, therefore cold, with complex atmospheric dynamics including the formation of ice clouds. Futuras observations will test the stability of these clouds at different points in Epsilon Indi Ab’s orbit.
Impacto on planetary atmospheric theories
Atmospheric models for cold giant planets have predicted everything but abundant water ice in the upper atmosphere. The MPIA team’s analysis indicates that vertical transport processes are more active than previously assumed. Sem clouds in the models, simulations of emitted light did not match the JWST data.
The next iterations of atmospheric codes will have to include ice clouds as a standard element. Essa revision appears to be minor, but it has a huge impact. The accuracy of atmospheric models is a fundamental basis for identifying biosignals and indicators of habitability on other worlds.
The finding of Epsilon Indi Ab complements previous JWST studies. The exoplanet LHS 3844 b showed a surface without an atmosphere, while Epsilon Indi Ab demonstrates an atmosphere with a dynamic climate. The two results form a spectrum of what can be expected on exoplanets: from dry rocky worlds to gas giants with complex meteorology.
Contexto: other exoplanet atmospheres mapped by Webb
JWST significantly expanded the catalog of exoplanetary atmospheres in just a few years:
- WASP-39b detected the first presence of carbon dioxide in the atmosphere outside Sistema Solar in 2022, followed by sulfur dioxide in 2023
- WASP-107b showed in 2024 clouds of helium escaping into space, evidence of continued atmospheric loss
- K2-18b generated controversy with the possible detection of dimethyl sulfide in 2023-2025, a molecule associated with microbial life, but independent replications in 2026 did not confirm the signal
- Sistema TRAPPIST-1 remains a priority, with observations indicating that the inner planets appear to have lost atmosphere
- TOI-561 b revealed unexpected thick atmosphere in 2026, expanding observed diversity
Brazilian Participação on exoplanet discoveries
Brasil has a direct contribution to recent discoveries. A national team discovered the exoplanet TOI-4562c in collaboration with Chilean and German scientists in 2024. The country is a partner in international consortia including SOAR in Cerro Pachón, Vera C. Rubin Observatory (LSST) and Cherenkov Telescope Array (CTA), guaranteeing observation time on cutting-edge equipment.
The SPARC4 program based on Pico of Dias and Minas Gerais monitors exoplanets in international collaboration. Universidades Brazilian companies such as USP, UFRJ and UFRN train specialists in exoplanetology through dedicated postgraduate programs. Brasileiros participate as co-authors in some international teams via cooperation with MPIA and ESO.
Brasil does not yet have formal institutional participation in the James Webb mission. NASA’s Conforme timeline, future missions such as Habitable Worlds Observatory (HWO), scheduled for the 2040s, may include more structured Brazilian participation. The current investment in national scientific training prepares the country for this future scenario.
Próximos steps and observational horizon
The MPIA team already has similar cold giant planets in the queue for future observation by JWST. Nos next observation cycles, other nearby systems will be targets of investigation with a methodology similar to that applied in Epsilon Indi Ab.
Nancy Grace Roman Space Telescope, scheduled to launch in 2027, will expand the catalog of giant planets in wide orbits. The established method for Epsilon Indi Ab will have more targets available in a few years. The Habitable Worlds Observatory (HWO), a successor telescope planned for the 2040s, will inherit the function of mapping large-scale atmospheres, focusing on the search for oxygen, ozone, methane and other indicators of habitability.
Epsilon Indi Ab works as a pilot project. Ele establishes the method and sensitivity needed for systematic campaigning over the next 20 years. The discovery also attracts new funding for exoplanetology programs at European and American universities, feeding back into the cycle of technological innovation in space instrumentation.