ASU researchers address methane mystery of exoplanet

ASU researchers address methane mystery of exoplanet
by Clarence Oxford
Los Angeles CA (SPX) May 22, 2024

In the effort to understand a warm gas-giant exoplanet, Arizona State University researchers have helped uncover its secrets.

WASP-107b has puzzled astronomers for some time, but recent findings with NASA's James Webb Space Telescope and the Hubble Space Telescope have provided new insights into its unusual characteristics.

A key revelation in the exploration of WASP-107b is the unexpected lack of methane, or CH4, in its atmosphere. This discovery, suggesting a hotter interior and a more massive core than previously thought, has been a focus of the research led by Luis Welbanks, a NASA Sagan Postdoctoral Fellow at the School of Earth and Space Exploration at ASU and lead author on a paper published in Nature.

The high temperature is believed to result from tidal heating caused by the planet's slightly noncircular orbit.

"Based on its radius, mass, age and assumed internal temperature, we thought WASP-107b had a very small, rocky core surrounded by a huge mass of hydrogen and helium," Welbanks said. "But it was hard to understand how such a small core could sweep up so much gas and then stop short of growing fully into a Jupiter-mass planet."

Welbanks and the team's analysis, along with data from the Hubble Space Telescope, has led to a deeper understanding of WASP-107b's composition and dynamics. The planet's inflated atmosphere results from internal heat and tidal forces, rather than extreme formation scenarios.

WASP-107b, a Neptune-like exoplanet discovered in 2017, has become a key subject for studying low-density exoplanets. Its unique characteristics, providing valuable insights into planetary evolution and atmospheric dynamics, have been unraveled through advanced spectroscopic techniques by the researchers. The information about the molecules present in WASP-107b's atmosphere, including the simultaneous detection of carbon-, oxygen-, nitrogen- and sulfur-bearing molecules for the first time in a transiting exoplanet, highlights its scientific value.

"The Webb data tells us that planets like WASP-107b didn't have to form in some odd way with a super small core and a huge gassy envelope," said Mike Line, associate professor in the School of Earth and Space Exploration at ASU. "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 research on WASP-107b underscores the importance of collaborative efforts in advancing our understanding of exoplanets. The research team's contribution, along with the support of NASA's James Webb Space Telescope and the Hubble Space Telescope, has been crucial in this endeavor.