In a groundbreaking study led by the Max Planck Institute for Solar System Research (MPS), astronomers have proposed a novel way to determine the true size of an exoplanet. This new method involves taking into account the magnetic field of the star around which the exoplanet orbits. The research, published in Nature Astronomy, sheds light on a significant factor that has been overlooked in previous studies of exoplanets.

The study focused on the exoplanet WASP-39b, a gas giant discovered orbiting a G-type star by the Wide Angle Search for Planets (WASP) consortium. WASP-39b, also known as “Bocaprins,” is one of the many “hot Jupiters” found in close proximity to its parent star. The researchers observed that traditional methods of analyzing light curves to determine the size of exoplanets were hindered by a discrepancy in the data.

Dr. Nadiia M. Kostogryz and her team of international collaborators from institutions such as Heidelberg University, Keele University, MIT, and STScI found that including the star’s magnetic field in their calculations helped resolve the discrepancies in the observational data. By considering the impact of the star’s magnetic field on the light curves, the researchers were able to accurately determine the size of the exoplanet.

The researchers used data from NASA’s Kepler Space Telescope to model the effects of the star’s magnetic field on the observed light curves. They found that the presence of a magnetic field influenced the shape of the light curve, particularly the limb darkening effect caused by the outer layers of the star appearing darker to the observer. By incorporating the magnetic field into their calculations, the researchers were able to reproduce the observational data more accurately.

Furthermore, the study revealed that the strength of the star’s magnetic field had a significant impact on limb darkening, with stars possessing stronger magnetic fields exhibiting less pronounced limb darkening. The researchers also extended their simulations to include data from the James Webb Space Telescope (JWST) and found that the magnetic field influenced limb darkening differently at various wavelengths.

These findings have important implications for the field of exoplanet research, as they provide a new framework for determining the true size of exoplanets based on the magnetic field of their parent stars. Dr. Alexander Shapiro, a coauthor of the study, emphasized the importance of refining models to interpret data from space telescopes like JWST.

Looking ahead, the researchers plan to apply their method to stars beyond the Sun, potentially leading to more accurate estimates of exoplanet characteristics, including mass for rocky planets similar to Earth. Additionally, the study highlights the potential for using light curves of stars to constrain the strength of their magnetic fields, a challenging measurement.

This groundbreaking research opens up new possibilities for understanding exoplanets and their host stars, paving the way for more precise and in-depth studies in the future.

References: MPS, Nature Astronomy