Interior of "cotton candy" exoplanet WASP-107 b revealed by Webb

Recent research using the James Webb Space Telescope has revealed new insights into the structure of the exoplanet WASP-107 b, a gas giant with a surprisingly low density.

This discovery marks the first time scientists have measured an exoplanet’s core mass, providing critical data for future studies of planetary atmospheres and interiors.

Inner core of exoplanet WASP-107 b

“Looking into the interior of a planet hundreds of light-years away sounds almost impossible,” explained lead author David Sing, a professor of earth and planetary sciences at Johns Hopkins University.

However, by knowing key characteristics such as the planet’s mass, radius, atmospheric composition, and internal temperature, researchers can gain valuable insights into its internal structure and the density of its core.

Sing emphasized that, thanks to the Webb telescope, this approach can now be applied to numerous gas planets across various star systems.

The analysis revealed that the exoplanet WASP-107 b has a core 12 times more massive than the Earth’s and contains a thousand times less methane than expected.

This low-density planet, roughly the size of Jupiter but only a tenth of its mass, has baffled scientists because of its “puffy” appearance.

Despite containing methane, a building block of life on Earth, WASP-107 b is not habitable due to its proximity to its star and lack of a solid surface.

Less methane, more carbon compounds

“We want to look at planets more similar to the gas giants in our own solar system, which have a lot of methane in their atmospheres,” Sing continued. “This is where the story of WASP-107 b got really interesting, because we didn’t know why the methane levels were so low.”

The new findings suggest that the methane on WASP-107 b transforms into other compounds as it moves upward from the planet’s interior, interacting with various chemicals and starlight in the upper atmosphere.

The team also detected sulfur dioxide, water vapor, carbon dioxide, and carbon monoxide, finding that the exoplanet WASP-107 b has more heavy elements than Uranus and Neptune.

“The planet has a hot core, and that heat source is changing the chemistry of the gasses deeper down, but it’s also driving this strong, convective mixing bubbling up from the interior,” noted co-author Zafar Rustamkulov, a Johns Hopkins doctoral student in planetary science.

“We think this heat is causing the chemistry of the gasses to change, specifically destroying methane and making elevated amounts of carbon dioxide and carbon monoxide,” Rustamkulov concluded.

Exoplanet WASP-107 b: Beyond the core

WASP-107 b is an exoplanet orbiting the star WASP-107, located about 212 light-years from Earth in the constellation Virgo. Here are some additional details about this intriguing exoplanet:

Discovery and basic characteristics

WASP-107 b was discovered in 2017 by the Wide Angle Search for Planets (WASP) project using the transit method. This method detects planets by observing the dimming of a star’s light as a planet passes in front of it.

The planet completes an orbit around its star in just 5.7 days, making it a “hot Jupiter” due to its close proximity to the star. WASP-107 b has a radius roughly equal to that of Jupiter but a much lower mass, only about one-tenth of Jupiter’s mass. This results in its extremely low density and “puffy” appearance.

WASP-107 b’s atmosphere and host star

Before the JWST study, the Hubble Space Telescope and other instruments observed WASP-107 b, identifying water vapor in its atmosphere.

Earlier studies suggested that WASP-107 b might have a hazy atmosphere with high-altitude clouds. These clouds could obscure some of the spectral features of the gases present.

WASP-107 is a K-type star, cooler and smaller than the Sun. Its characteristics play a crucial role in the atmospheric conditions of WASP-107 b.

Tidal forces keeping the core hot

These findings highlight the connection between an exoplanet’s core and its atmospheric composition. The study shows how tidal forces from the star might heat the planet’s core, affecting its overall thermodynamics and observable atmosphere.

“The Webb data tells us that planets like WASP-107 b didn’t have to form in some odd way with a super small core and a huge gassy envelope,” explained Mike Line, an astrophysicist at Arizona State University.

“Instead, we can take something more like Neptune, with a lot of rock and not as much gas, just dial up the temperature, and poof it up to look the way it does.”

The Johns Hopkins team plans to continue investigating what keeps the core of WASP-107 b so hot, possibly examining the stretching and pulling forces exerted by its star.

Webb and the future of exoplanet research

In summary, these new discoveries about WASP-107 b, made possible by the James Webb Space Telescope, mark a significant milestone in our understanding of exoplanets and their atmospheres.

As scientists continue to explore the complexities of planetary systems, the insights gained from studying this marshmallow-like planet and other gas giants will undoubtedly shape future research.

With its surprisingly low methane levels, massive core, and the clearest connection yet established between an exoplanet’s interior and atmosphere, WASP-107 b has opened up new avenues for investigation.

As we look to the future, the search for habitable worlds and the exploration of the vast diversity of exoplanets will only intensify, driven by the remarkable advancements in technology and the unwavering curiosity of the scientific community.

The study is published in the journal Nature.

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