Mass motions in the photosphere of Betelgeuse

Spectroscopic observations of Betelgeuse, taken at the Elginfield Observatory, show velocity and temperature variations delineating the systematic, but generally chaotic, rise and fall of photospheric material. The characteristic timescale of the variations is 400 days, while velocities cover a range of similar to 9 km s(-1). Macroturbulence is constant to about 13% and does not result from motions on the largest scales, but from motions within the large structures. The line bisectors have predominantly a reversed-C shape. Variations in the shapes of bisectors occur on the 1 km s(-1) level and are not obviously connected to their shifts in wavelength. A likely explanation of the observations is granulation and giant convection cells accompanied by short-lived oscillations they trigger. Random convection events may account for radial-velocity jitter seen in many highly evolved stars.