Low-mass stars in the Milky Way galaxy harbor surprisingly strong magnetic fields

Indeed, the rotation of our sun is intricately connected to the magnetic phenomena it exhibits. "Differential rotation is thought to be responsible for the dynamo process in stars like our Sun, driving magnetic activity and starspots," the study mentions.

For this study, the researchers analyzed data publicly available from the Sloan Digital Sky Survey. They focused on a sample of 136 stars in M44, also known as Praesepe or the Beehive cluster.

The research found the presence of far more surface magnetic activity than predicted by existing models.

The detailed analysis identified an internal process known as core-envelope decoupling, which may be controlling the surface magnetic activity of these stars. 

In this process, the surface and core of the star begin to spin at the same rate, then progressively drift apart — indicating variation in the stellar spin rate. 

Study essential to zero down on habitable world locations

With this rotational anomaly, the high radiation emitted by stars might continue to last for billions of years, thereby influencing the likelihood of finding habitable exoplanets in their systems. 

“Stars experiencing this enhanced magnetism are likely going to be battering their planets with high-energy radiation,“ noted Lyra Cao, lead author of the study.

Cao added: “This effect is predicted to last for billions of years on some stars, so it’s important to understand what it might do to our ideas of habitability.”

The new findings might help narrow down the hunt for possibly habitable outer planets in the Milky Way galaxy. Furthermore, the research might be valuable in developing better theoretical models of star evolution. 

“The next thing to do is verify that enhanced magnetism happens on a much larger scale. If we can understand what’s going on in the interiors of these stars as they experience shear-enhanced magnetism, it’s going to lead science in a new direction,” concluded Cao. 

The results are published The Astrophysical Journal Letters.

Study Abstract:

Differential rotation is thought to be responsible for the dynamo process in stars like our Sun, driving magnetic activity and starspots. We report that starspot measurements in the Praesepe open cluster are strongly enhanced only for stars that depart from standard models of rotational evolution. A decoupling of the spin-down history between the core and envelope explains both the activity and rotation anomalies: surface rotational evolution is stalled by interior angular momentum redistribution, and the resultant radial shears enhance starspot activity. These anomalies provide evidence for an evolving front of shear-enhanced activity affecting the magnetic and rotational evolution of cool stars and the high-energy environments of their planetary companions for hundreds of millions to billions of years on the main sequence.