Magnetic fields play a crucial role in determining the characteristics of exoplanets orbiting stars. New model calculations presented in Nature Astronomy by the Max Planck Institute for Solar System Research show that a star’s level of magnetic activity affects the distribution of brightness over its disk, impacting the observational data of exoplanets. This new model is essential for correctly interpreting data from space telescopes such as Kepler, James Webb, or PLATO, aimed at studying distant worlds outside our Solar System.
A notable example is WASP-39b, a gas giant orbiting the star WASP-39 in the constellation Virgo, 700 light years away from Earth. Observations by the James Webb Space Telescope revealed the presence of water vapor, methane, and carbon dioxide in WASP-39b’s atmosphere. However, researchers faced challenges in reproducing crucial details of the observations in model calculations, hindering more precise analysis of the data. A new study led by the MPS offers a solution to overcome these obstacles, involving researchers from various institutions around the world.
Interpreting data from exoplanets involves analyzing the light curves of stars, which measure their brightness over time. The effects of exoplanets passing in front of their stars can be observed in the light curve as a drop in brightness, providing information about the size, orbital period, and atmospheric composition of the planet. However, difficulties arise in accurately representing these observations using conventional models due to the phenomenon of limb darkening, where the edge of a star appears darker to an observer.
The limb darkening effect on the light curve is influenced by the star’s magnetic field, which has been missing in previous model calculations. Including the magnetic field in the models reveals that the strength of the field determines the degree of limb darkening, with stars exhibiting a weak magnetic field showing more pronounced darkening. By including the magnetic field in the computations, discrepancies between observational data and model calculations are eliminated, as demonstrated by analyzing data from NASA’s Kepler Space Telescope.
Furthermore, the team extended their analyses to data from the James Webb Space Telescope, which can observe stars at various wavelengths to search for specific molecules in exoplanet atmospheres. The magnetic field of the parent star was found to influence limb darkening differently at different wavelengths, highlighting the need to consider the magnetic field in future evaluations for more precise results. This research emphasizes the importance of refining models to interpret data from advanced space telescopes accurately, paving the way for further advancements in exoplanet research.
Moving forward, the researchers aim to expand their analyses to stars different from the Sun and utilize the light curves of stars with exoplanets to estimate the strength of the stellar magnetic field. By incorporating the magnetic field in their models, scientists can improve the accuracy of interpreting observational data from space telescopes, enhancing our understanding of exoplanets orbiting distant stars.