In a recent study, an international team of researchers led by Dr. S. Bellotti from the University of Hamburg, along with colleagues from institutions across Europe and the United States, has delved into the magnetic properties of stars hosting exoplanets. Their work is part of a broader effort to prepare for the upcoming Ariel mission, a space telescope designed to study the atmospheres of exoplanets.
The researchers focused on 15 stars of spectral types G and M, which are similar to our Sun and slightly cooler, respectively. They used advanced spectropolarimetric instruments like Neo-Narval, HARPSpol, and SPIRou to detect and characterize the magnetic fields of these stars. For three of the stars—TOI-1860, DS Tuc A, and HD 63433—they were able to reconstruct the topology of the magnetic fields and observe how these fields evolve over time using a technique called Zeeman-Doppler imaging (ZDI). This method allows scientists to map the magnetic fields of stars by analyzing the polarization of light emitted from their surfaces.
The study found that the large-scale magnetic fields of these stars are moderately strong, ranging from 30 to 60 Gauss on average, and are quite complex. A significant portion of the magnetic energy is found in the toroidal component, which wraps around the star like a ring, and in high-order poloidal components, which extend out from the star’s surface. The researchers also performed 3D magnetohydrodynamic (MHD) simulations to model the stellar wind and the environment around these stars, which has implications for the exoplanets orbiting them.
One of the key findings is that the orbit of the exoplanet TOI-1860 b is almost entirely within the sub-Alfvénic regime, meaning the planet is constantly exposed to the star’s magnetic field. This could have significant implications for the planet’s atmosphere and potential habitability. In contrast, the exoplanets DS Tuc A b and HD 63433 d have orbits that are trans-Alfvénic, spending part of their time inside and part outside the star’s magnetic influence. The exoplanets HD 63433 b and c are in the super-Alfvénic regime, meaning they are largely outside the star’s magnetic field.
The researchers also found that the magnetic field of HD 63433 has evolved over time, which has affected the sub-Alfvénic nature of the orbit of HD 63433 c. This temporal evolution is an important factor to consider when studying the interaction between stars and their planets.
For the energy sector, understanding the magnetic properties of stars and their influence on exoplanets can provide insights into the conditions necessary for planetary habitability and the potential for harnessing stellar energy. While this research is primarily focused on exoplanets and stellar physics, the techniques and knowledge gained can be applied to better understand the Sun’s magnetic field and its impact on Earth’s energy systems, such as satellite communications and power grids. The study was published in the journal Astronomy & Astrophysics.
This article is based on research available at arXiv.