The many faces of Betelgeuse

TL;DR

This study uses interferometric data to analyze Betelgeuse's surface and atmospheric variability, revealing changes in size, temperature, and asymmetry over several years, suggesting an evolving circumstellar shell.

Contribution

First high-resolution interferometric observations at 11.15 microns showing Betelgeuse's surface variability over multiple years.

Findings

Betelgeuse's size varies over time.

Effective temperature and asymmetry change significantly.

Evidence of an evolving optically thick shell near the star.

Abstract

The dynamics of the surface and inner atmosphere of the red supergiant star Betelgeuse are the subject of numerous high angular resolution and spectroscopic studies. Here, we present three-telescope interferometric data obtained at 11.15 microns wavelength with the Berkeley Infrared Spatial Interferometer (ISI), that probe the stellar surface continuum. We find striking variability in the size, effective temperature, and degree of asymmetry of the star over the years 2006-2009. These results may indicate an evolving shell of optically thick material close to the stellar photosphere.