Astronomers have found evidence that some stars boast unexpectedly strong surface magnetic fields, a discovery that challenges current models of how they evolve.
In stars like our sun, surface magnetism is linked to stellar spin, a process similar to the inner workings of a hand-cranked flashlight. Strong magnetic fields are seen in the hearts of magnetic sunspot regions, and cause a variety of space weather phenomena. Until now, low-mass stars — celestial bodies of lower mass than our sun that can rotate either very rapidly or relatively slowly — were thought to exhibit very low levels of magnetic activity, an assumption which has primed them as ideal host stars for potentially habitable planets.
In a new study, published today in The Astrophysical Journal Letters, researchers from The Ohio State University argue that a new internal mechanism called core-envelope decoupling — when the surface and core of the star start out spinning at the same rate, then drift apart — might be responsible for enhancing magnetic fields on cool stars, a process which could intensify their radiation for billions of years and impact the habitability of their nearby exoplanets.
The research was made possible due to a technique that Lyra Cao, lead author of the study and a graduate student in astronomy at Ohio State, and co-author Marc Pinsonneault, a professor of astronomy at Ohio State, developed earlier this year to make and characterize starspot and magnetic field measurements.
Although low-mass stars are the most common stars in the Milky Way and are often hosts to exoplanets, scientists know comparatively little about them, said Cao.
For decades, it was assumed that the physical processes of lower mass stars followed those of solar-type stars. Because stars gradually lose their angular momentum as they spin down, astronomers can use stellar spins as a device to understand the nature of a star’s physical processes, and how they interact with their companions and their…