December 7, 2022

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Revealing new secrets of the “dynamo” stars

The abundance of heavy elements within a star plays an important role in the mechanisms that lead to the formation and reorganization of the large-scale magnetic field, a phenomenon called “stellar dynamo”. It is the result of the study led by two researchers from the National Institute of Astrophysics (INAF) in Catania, Alvio Bonanno and Enrico Corsaro, who have compiled the largest catalog of periods of stellar activity and the rotational cycle. The results were published in The Astrophysical Journal Letters.

The work is based on a new statistical approach applied to data collected by the Gaia satellite, the European Space Agency (ESA) mission that has been scanning the sky for more than eight years to create an increasingly accurate 3D map of our galaxy, the Milky Way. This combination allowed the assembly of a catalog of 67 stars (the largest of its kind to date) with periods of stellar activity and spin cycle measured.

Thus it was found that for some stars the frequency of the activity cycle increases with rotation, while for others it decreases. The sun belongs to the second category. “We also learned that stellar metallicity may be the element responsible for generating one type of dynamo rather than another, as metallicity alters the microscopic properties of a star’s convective region, the region within which stellar dynamos are thought to be generated,” explains Corsaro.

Stellar magnetic activity is one of the most difficult astrophysical phenomena to deal with and its origin is not yet fully understood. Improving knowledge of stellar magnetism is of fundamental importance for its impact on the evolution of stars, and thus on the evolution and habitability of potential planets orbiting stars.

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