Thermodynamics of dust condensation around the dimming Betelgeuse

Abstract

ABSTRACT Betelgeuse is one of the brightest red supergiant (RSG) stars because of its proximity to the Solar system. This makes it important when deducing the features and evolutionary phases of RSG stars. Betelgeuse has always been a well-observed target but especially during the past year, because of the reduction in its brightness. It has been speculated that the star is in its last evolutionary stage(s), and that it is soon going to explode. However, in recent work, it has been proposed that the episodic mass loss and dust condensation around the star are major reasons for the reduction in its brightness. In this work, we have performed detailed thermodynamical equilibrium and non-equilibrium calculations of the condensation of dust grains around the cooling envelope of Betelgeuse. Based on the deduced chemical composition, we have ventured to determine the nature of dust that could condense in the stellar winds. The dust grains are essentially found to be oxides of Al, Ca and Ti, and silicates of Al, Ca, Mg and Fe-metal. Further, we have determined the normalized masses of the dust grains of various compositions that could be present around the star and could be causing the reduction in its brightness.