The James Webb Space Telescope has made the first direct analysis of clouds on a nearby alien world. These aren’t just made of water vapor but also sand, which would move around the planet much like Earth’s water cycle.
Located just 200 light-years from Earth, the exoplanet in question is known as WASP-107b, and it’s already attracted some attention for being a bit of an oddball. It’s about the size of Jupiter but only has the mass of Neptune, which makes it one of the least dense planets found so far. In fact, this extreme “cotton candy” consistency may raise questions about how gas giant planets even form.
On the plus side, this fluffiness allowed astronomers to peer deeper into the planet’s atmosphere and analyze its chemical composition. Using James Webb’s intense infrared eyes, the scientists were able to detect water vapor, sulfur dioxide and silicates. Water vapor was to be expected, but the sulfur dioxide was a surprise, according to the team – early models of the atmosphere predicted it wouldn’t be there. Instead, methane was notably absent.
But the most intriguing find was the clouds, which are eerily alien – Webb found that they were made of silicates, ie. sand, which would evaporate up and rain back down in a similar cycle to water on Earth.
“The fact that we see these sand clouds high up in the atmosphere must mean that the sand rain droplets evaporate in deeper, very hot layers and the resulting silicate vapor is efficiently moved back up, where they recondense to form silicate clouds once more,” said Dr. Michiel Min, lead author of the study. “This is very similar to the water vapor and cloud cycle on our own Earth but with droplets made of sand.”
Clouds have been inferred to exist on other exoplanets before, usually through climate models and other types of observations. They can take on some bizarre forms too – rocks, gemstones like rubies and sapphires, or even titanium that reflects starlight like giant mirrors. But the team says this marks the first direct chemical analysis of clouds on a planet beyond our solar system.
The team also developed a new climate model of WASP-107b that helps explain the surprising detection of sulfur dioxide. Again, it comes down to that fluffy atmosphere, which allows light from its parent star to penetrate deeper, triggering the chemical reactions that produce sulfur dioxide.
The researchers say that this study highlights how James Webb can improve our understanding of distant planets.
The research was published in the journal Nature.
Source: KU Leuven