Using James Webb Space Telescope data, scientists have made the first measurements of an exoplanet’s core mass. Scientists detected a surprisingly low amount of methane and a super-sized core hiding within the cotton candy-like planet WASP-107 b.
The findings represent the first measurements of an exoplanet’s core mass. They will serve as a foundation for upcoming research on planetary interiors and atmospheres, an important study area in hunting for habitable worlds outside our solar system.
Lead author David Sing, a Bloomberg Distinguished Professor of Earth and Planetary Sciences at Johns Hopkins University, said, “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 hotness 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. This is now something we can do for lots of different gas planets in various systems.”
WASP-107 b is a massive planet orbiting a star around 200 light-years away, shrouded in a hot atmosphere as fluffy as cotton. Its composition—a planet the size of Jupiter with a mass only a tenth that of that planet—makes it spherical.
The planet’s lack of a solid surface and proximity to its parent star makes it uninhabitable even if it contains methane, a necessary component of life on Earth. However, it might include significant hints of late-stage planetary evolution.
Other scientists used the Webb telescope to detect methane in a different study. Their findings revealed comparable details regarding the planet’s size and density.
Scientists had hypothesized that an internal heat source on the planet caused its expanded radius, according to Zafar Rustamkulov, a planetary science PhD student at Johns Hopkins who co-led the study. The researchers explained how the planet’s thermodynamics affects its observable atmosphere by integrating Webb’s measurements of WASP-107 b with simulations of the planet’s internal physics and 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 said. “We think this heat is causing the chemistry of the gases to change, specifically destroying methane and making elevated amounts of carbon dioxide and carbon monoxide.”
According to Rustamkulov, the latest findings show the most vital link between an exoplanet’s innards and its upper atmosphere. Last year, the Webb telescope discovered sulfur dioxide on WASP-39, a separate exoplanet located around 700 light-years distant. This discovery represents the first proof of an atmospheric component produced by reactions fueled by starlight.
The Johns Hopkins team is currently concentrating on possible core heat-retaining factors and anticipates the presence of forces akin to those responsible for Earth’s ocean’s high and low tides. They want to see if the planet’s star is pulling and stretching it, and if so, how that may explain the high temperature in the core.
Journal Reference:
- Sing, D.K., Rustamkulov, Z., Thorngren, D.P. et al. A warm Neptune’s methane reveals core mass and vigorous atmospheric mixing. Nature (2024).DOI: 10.1038/s41586-024-07395-z