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The evolved stages of massive stars are poorly understood, but invaluableconstraints can be derived from spatially resolved observations of nearby redsupergiants, such as Betelgeuse. ALMA observations of Betelgeuse showing adipolar velocity field have been interpreted as evidence for a rotation rate of$v\sin i \sim 5\, \mathrm{km\, s^{-1}}$. This is two orders of magnitude largerthan predicted by single-star evolution, leading to the suggestion thatBetelgeuse is a binary merger product. We propose instead that the velocityfield could be due to large-scale convective motions. The resulting surfacevelocity maps can sometimes be mistaken for rotation, especially when theturbulent motions are only partially resolved, as is the case for the currentALMA beam. We support this claim with 3D CO5BOLD simulations of non-rotatingred supergiants post-processed to predict synthetic ALMA images and SiO spectrato compare with observed radial velocity maps. Our simulations show a $\sim50\%$ chance to be interpreted as evidence for a rotation rate as high asclaimed for Betelgeuse. We conclude that we need at least another ALMAobservation to firmly establish whether Betelgeuse is indeed rapidly rotating.Such observations would also provide insight into the role of angular momentumand binary interaction in the late evolutionary stages. The data will furtherprobe the structure and complex physical processes in the atmospheres of redsupergiants, which are immediate progenitors of supernovae and are believed tobe essential in the formation of gravitational wave sources.

Is Betelgeuse really rotating? Synthetic ALMA observations of large-scale convection in 3D simulations of Red Supergiants