Scientists have detected water ice clouds in the atmosphere of a giant exoplanet using the James Webb Space Telescope, a finding that challenges existing models of gas giant formation and evolution.
The discovery was made on Epsilon Indi Ab, a planet orbiting the star Epsilon Indi A approximately 12 light-years from Earth, by a team led by Elisabeth Matthews at the Max Planck Institute for Astronomy. Using JWST’s mid-infrared instrument MIRI, the researchers directly imaged the planet, which has a mass of 7.6 times that of Jupiter but a similar diameter.
This marks one of the first detailed atmospheric studies of a true Jupiter analogue — a gas giant with temperatures and formation history comparable to those in our solar system. Most previously observed exoplanets of similar size are much hotter due to their close orbits, making them poor analogs for studying Jupiter-like conditions.
The presence of water ice clouds suggests the planet’s atmosphere is cooler and more chemically complex than predicted, indicating that current models may underestimate the role of atmospheric dynamics and cloud formation in regulating heat and chemistry on distant worlds.
According to Matthews, JWST now enables detailed study of solar-system analogue planets in a way that was previously impossible, though studying Earth-like worlds will require even more advanced telescopes. Bhavesh Rajpoot, a PhD student at MPIA, noted the planet’s greater mass despite its Jupiter-like size, hinting at a denser internal composition.
The findings represent a methodological advance in exoplanet science, demonstrating that direct imaging in mid-infrared wavelengths can reveal atmospheric features on cold, distant gas giants — a critical step toward characterizing potentially habitable worlds.
Why is detecting ice clouds on this exoplanet significant?
It challenges existing atmospheric models by showing greater complexity in a Jupiter-like planet than expected, suggesting current theories may not fully account for cloud formation and heat regulation in cold gas giants.
How did the team observe the planet’s atmosphere?
They used the James Webb Space Telescope’s MIRI instrument to directly image Epsilon Indi Ab in mid-infrared light, allowing detailed study of its atmospheric composition without relying on transit methods.
