'Crucial milestone': Sand clouds and water vapour detected in exoplanet's atmosphere

WASP-107b is a unique gas giant, orbiting a star that is slightly cooler and less massive than our Sun.
WASP-107b is a unique gas giant, orbiting a star that is slightly cooler and less massive than our Sun. Copyright Klaas Verpoest, Johan Van Looveren, Leen Decin
By Lauren Chadwick
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Astronomers studied the atmosphere of an exoplanet using the James Webb Space Telescope.

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European astronomers have found water vapour, sulphur dioxide, and sand clouds in the atmosphere of an exoplanet using the James Webb Space Telescope, describing it as a "crucial" discovery.

Exoplanets are planets found beyond our solar system, with many orbiting other stars.

The new study, led by astronomers at KU Leuven, looked at an exoplanet named WASP-107b, which is a Neptune-like gas giant that was discovered in 2017.

It is more than 200 light-years away from Earth and is orbiting a star slightly smaller than the Sun. Its "thin atmosphere" allows astronomers to study its chemical composition.

"The fact that it has such a very puffy atmosphere enables us to really look very deep inside the atmosphere of the planet," Leen Decin, a professor from KU Leuven and one of the study's lead authors, told Euronews Next.

She compared it to looking through clouds: "If you have a very thick cloud, you and I cannot look through the cloud. But if you have an extremely thin cloud, we can look through that very thin cloud."

It's the same for the atmosphere and allows astronomers to learn more about the exoplanet.

The fact that it has such a very puffy atmosphere enables us to really look very deep inside the atmosphere of the planet.
Leen Decin
KU Leuven, Director of Institute of Astronomy

The researchers were surprised to detect sulphur dioxide, which smells like burning matches, in the atmosphere but no methane. Methane is a greenhouse gas and its absence indicates that the exoplanet has a warm core, they said.

The James Webb Space Telescope "is bringing about a scientific revolution in the field of exoplanet characterisation at an unprecedented pace," Decin said in a statement.

"The discovery of sand clouds, water vapour and sulphur dioxide in the tenuous atmosphere of this exoplanet by James Webb's MIRI instrument is a crucial milestone," she added.

The James Webb Space Telescope is a space science observatory and an international programme led by the US National Aeronautics and Space Administration (NASA), the European Space Agency (ESA) and the Canadian Space Agency and has rapidly changed the field of astronomy since its launch in 2021.

The researchers' findings were published in the journal Nature.

Clusters of sand

The astronomers also found that the clouds in the exoplanet's atmosphere are made up of silicon, which is the main component of sand.

"It is the first time in history that we can deduce the composition of the clouds. And so here are sand clouds, very, very small sand clouds and they exist very high up in the atmosphere of the planets," Decin told Euronews.

Michiel Min, from the Netherlands Institute for Space Research, said in a statement that the sand clouds high in the atmosphere have a similar cycle to the water vapour and cloud cycle on Earth but with "droplets made of sand".

Decin says you could also think of it as solid clusters of sand on an exoplanet with extremely high wind speeds of a few kilometres per second.

'Going beyond Earth-based knowledge'

The researchers say the observations provide important insights into the chemistry of this exoplanet.

They were particularly surprised to find sulphur dioxide because all of their models were predicting that they would not find that.

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"Maybe the most broad impact there is that our understanding of exoplanet atmospheres in general is still extremely limited, and the main reason for that is that our understanding is mainly based on what we know is happening here on Earth and also, what we know about chemistry is very much Earth-based," Decin said.

But this exoplanet is much warmer than planets in our solar system.

"This is what we do too often, if we only use our Earth-based knowledge and we think we understand what is happening on all the exoplanets and we implanted knowledge to another planet, we are just missing things," she said.

"So we are continuously pushed to broaden our horizons to go into that kind of a terra incognita and learn a lot of new things before we finally can understand what is happening on these planets".

This story has been updated with quotes from one of the study's lead authors.

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