Infrared observations of WASP 121 reveal stellar oscillations and surface granulation

Observations from the James Webb Space Telescope have successfully detected stellar oscillations and granulation on the star WASP 121 using infrared light. This is the first time these convective processes have been measured outside of optical wavelengths. The findings confirm that the strength of these signals decreases with longer wavelengths, though the pattern does not follow simple blackbody expectations.

Star system: WASP 121 | Distance from the Sun: 858 light years

Stellar oscillations are rhythmic pulses that ripple through a star, while granulation refers to the bubbling, convective surface pattern caused by the movement of heat from a star's interior to its outer layers. These processes provide essential clues about the internal physics of stars, yet they have historically been difficult to measure beyond optical light. Understanding these dynamics is necessary to refine models of how stars behave and how energy moves within them.

The James Webb Space Telescope recently captured detailed time-series data of the F6V main-sequence star WASP 121. While these observations were originally designed to analyze the atmosphere of an orbiting exoplanet, they provided a unique opportunity to monitor the star's surface activity. By analyzing these infrared light signals, the observations confirm that the intensity of both stellar oscillations and granulation decreases as the observed wavelength increases.

These results provide a new way to test complex three-dimensional convection models that describe how stars generate and transport heat. Furthermore, the measurement demonstrates that infrared observations can effectively isolate stellar signals from planetary data. This capability will be particularly valuable for future missions like the Roman Space Telescope, which will rely on precise asteroseismic data to characterize stars and their surrounding systems in the infrared spectrum.

Key findings
Stellar oscillations and granulation were successfully detected at infrared wavelengths for the first time.
The amplitudes of oscillations and granulation diminish as the wavelength increases.
The observed decrease in signal amplitude does not perfectly follow simple blackbody scaling.
The measurement enables more accurate separation of stellar and planetary signals in future transit observations.
These results validate the use of infrared time-domain data for future asteroseismic studies.

Scientific study

Detection of Solar-like Oscillations and Granulation at Infrared Wavelengths using JWST (external link)