Recent discoveries by the James Webb Space Telescope have unveiled surprising details about WASP-107 b, an exoplanet that has intrigued astronomers with its puffy, cotton candy-like appearance. The findings reveal an unexpectedly low amount of methane and a massive core, providing new insights into the planet's structure and composition.
WASP-107 b orbits a star roughly 200 light-years away from Earth. Despite its size, which is comparable to Jupiter, it has only a tenth of Jupiter's mass, making it remarkably lightweight and giving it a bloated, fluffy appearance. This low density has puzzled scientists, who have now begun to piece together the planet's complex nature.
The key to these revelations lies in the measurements of WASP-107 b's core and atmosphere, marking the first time researchers have been able to estimate the core mass of an exoplanet. David Sing, the lead author of the study and a Bloomberg Distinguished Professor of Earth and Planetary Sciences at Johns Hopkins University, highlighted the importance of these findings. “Looking into the interior of a planet hundreds of light-years away sounds almost impossible, but when you know the mass, radius, atmospheric composition, and the temperature of its interior, you've got all the pieces you need to get an idea of what's inside and how heavy that core is,” Sing said.
The study, published in Nature, found that WASP-107 b's core is about 12 times more massive than Earth's, a significant discovery that challenges previous assumptions about such low-density planets. Additionally, the planet has a thousand times less methane than expected, raising questions about its atmospheric chemistry and the processes taking place within it.
WASP-107 b's atmosphere is not considered habitable due to its close proximity to its parent star and lack of a solid surface. However, the presence of methane—a crucial component for life on Earth—along with other chemicals like sulfur dioxide, water vapor, carbon dioxide, and carbon monoxide, suggests complex chemical interactions influenced by the planet's intense heat and strong stellar radiation.
The low levels of methane have particularly intrigued scientists. Sing explained that methane likely transforms into other compounds as it rises through the planet's atmosphere, interacting with other chemicals and starlight. This discovery aligns with similar observations made by the Webb telescope on other exoplanets, further enhancing our understanding of atmospheric dynamics in extreme conditions.
In a complementary study also published in Nature, researchers used the Webb telescope to measure WASP-107 b's atmospheric composition and density, providing consistent data about the planet's surprising lack of methane and its heavy-element-rich atmosphere, which is more abundant in elements than Uranus and Neptune.
The chemical profile of WASP-107 b is helping scientists understand how planetary atmospheres evolve under harsh conditions. “We had never been able to study this mixing process in an exoplanet atmosphere in detail,” Sing noted. “This will go a long way in understanding how these dynamic chemical reactions operate, something we definitely need as we start looking at rocky planets and biomarker signatures.”
Zafar Rustamkulov, a Johns Hopkins doctoral student in planetary science who co-led the research, pointed out that the planet's overinflated radius might be due to an internal heat source. By combining atmospheric and interior physics models with data from the Webb telescope, the team explored how the planet's thermodynamics influence its observable atmosphere.
“The planet has a hot core, and that heat source is changing the chemistry of the gases deeper down, but it's also driving this strong, convective mixing bubbling up from the interior,” Rustamkulov explained. “We think this heat is causing the chemistry of the gases to change, specifically destroying methane and creating elevated amounts of carbon dioxide and carbon monoxide.”
These findings offer the clearest connection yet between an exoplanet's interior and its atmospheric composition. Last year, the Webb telescope detected sulfur dioxide in WASP-39, another exoplanet, marking the first evidence of an atmospheric compound created by reactions driven by starlight.
Looking ahead, the Johns Hopkins team plans to investigate what sustains the high heat in WASP-107 b's core. They hypothesize that tidal forces, similar to those causing high and low tides on Earth, might be at work. By studying these forces, they hope to gain a deeper understanding of the mechanisms heating the planet's core and driving its dynamic atmosphere.
These groundbreaking discoveries about WASP-107 b not only enhance our knowledge of exoplanetary atmospheres and interiors but also pave the way for future studies of habitable worlds beyond our solar system.
Source: Johns Hopkins University