James Webb space telescope uncovers water vapour and sand clouds on exoplanet

Study reveals the intriguing composition of WASP-107b3's atmosphere, offering insights into its formation and evolution

Artist's impression of WASP-107b and its parent star. Illustration: LUCA School of Arts, Belgium/ Klaas Verpoest (visuals), Johan Van Looveren (typography)

The James Webb Space Telescope has detected water vapour, sulphur dioxide, and silicate sand clouds in the atmosphere of the exoplanet WASP-107b3.

The discovery was made by a team of European astronomers, co-led by researchers from the Institute of Astronomy at KU Leuven in Belgium.

Prof Leen Decin, a lead author of the study, told The National: “The chemistry and dynamics are quite different compared to what we expected.”

The exoplanet orbits WASP-107, a star slightly cooler and less massive than our Sun, 200 light-years away from Earth in the constellation Virgo.

Its unique gaseous composition and “fluffy” atmosphere, larger in size than Neptune but similar in mass, allowed for a deeper atmospheric exploration.

Using the telescope's Mid-Infrared Instrument (MIRI), the researchers revealed the explonet's intriguing atmospheric composition.

“Before using the James Webb Space Telescope we knew it had water vapour, but this is the first time we have been able to identify the chemical composition of the clouds,” Prof Decin, of KU Leaven, said.

“We still cannot understand how that planet has formed and evolved. We have found that the planet is extremely close to its mother star,” she told The National.

“We think it has formed further out, and has migrated little by little closer to its host star,” she said.

The discovery of WASP-107b3 was announced in 2017 by a team led by D R Anderson via the WASP-South observatory in South Africa.

The absence of methane, a notable finding from their observations, suggests a potentially warm interior of the planet and an active movement of heat energy.

The detection of sulphur dioxide was a surprise as it was previously thought to be absent in such environments.

Prof Decin said WASP-107b's low-density atmosphere played a role in the formation of the gas.

The discovery indicates a dynamic atmosphere where high-energy photons from the planet's host star trigger necessary chemical reactions.

The study, published in the journal Nature, also observed that the spectral features of sulphur dioxide and water vapour were less pronounced than expected in a cloudless environment, leading to the discovery of high-altitude silicate clouds.

These clouds, composed of small silicate particles similar to sand, are a new discovery in the field of exoplanetary studies.

Lead author Dr Michiel Min explained that a cycle of sublimation and condensation through vertical transport formed the sand clouds at high altitudes in WASP-107b's atmosphere.

“This is very similar to the water vapour and cloud cycle on our own Earth but with droplets made of sand,” Dr Min said.

Dr Achrene Dyrek at CEA Paris emphasised the role of the James Webb Space Telescope (JWST) in enabling deep atmospheric characterisation of exoplanets, unravelling previously unknown aspects.

“JWST enables a deep atmospheric characterisation of an exoplanet that does not have any counterpart in our Solar System, we are unravelling new worlds!”, says Dr Dyrek.

Contributions to the MIRI instrument, pivotal in these discoveries, came from Belgian scientists and engineers, funded by the Belgian federal science policy office BELSPO via the ESA PRODEX programme.

Collaborative efforts from the Centre Spatial de Liege, Thales Alenia Space, OIP Sensor Systems, and the Institute of Astronomy at KU Leuven played a key role in the instrument's development and testing.

Instrument specialist Dr Bart Vandenbussche of KU Leuven expressed pride in the instrument's success, stating, “It is rewarding to see our instrument unravel the atmosphere of this intriguing exoplanet.”

The findings from the JWST are reshaping our knowledge of planetary atmospheres, highlighting the diverse climatic and chemical interactions occurring in these distant worlds.

Prof Decin told The National: “We are still lacking so much understanding on how physics and chemistry actually act together.

“Nobody here on Earth is interested in measuring these chemical reactions. They are of no use for industries, for the car industry, for instance, they are not of no use there.

“So we always have that horizon. But it's horizon based on what we know from Earth. And we always have to go beyond that horizon, to touch new grants and to find new understanding.”