On January 22, 2025, the Institute of Astronomy with NAO-BAN announced a significant scientific achievement for 2024: the study of magnetic activity in the red giant star RZ Ari, located in the constellation Aries, due to planet ingestion. The results, led by Bulgarian researcher Prof. Dr. Renada Konstantinova and four other scientists, were published in the esteemed journal Astronomy & Astrophysics.
The research team included scientists from France, the USA, Brazil, and Chile. The investigation revealed that RZ Ari has evolved to the peak of the red giant branch or beyond the helium-burning stage. The evolutionary stage of the star suggests that its magnetic activity is not caused by a solar-type dynamo (alpha-omega).
Analysis of the star's parameters—rotation, chemical abundances, and magnetic field strength—indicates the possible influence of an alternative dynamo mechanism. The star's rotation is accelerated, and its lithium content is unusually high.
These parameters, along with the fact that the star is positioned far from the so-called 'second magnetic strip' on the Hertzsprung-Russell diagram, where known pre-evolved red giants with magnetic fields are concentrated, suggest that the magnetic dynamo action in RZ Ari may be a result of planet ingestion.
For the first time, a magnetic field map of a star in such an advanced evolutionary stage has been created, showing the presence of poloidal and toroidal components, consistent with dynamo theory. There are also indications of large convective structures on the giant's surface, which may suggest local dynamo action, similar to that of the supergiant Betelgeuse. However, analysis of spectropolarimetric and photometric data indicates that even if such influence exists, its contribution to the magnetic field and activity of RZ Ari is not predominant.