The nearby red supergiant (RSG) Betelgeuse has a complex circumstellar medium out to at
least 0.5 parsecs from its surface, shaped by its mass-loss history within the past ≈ 0.1
Myr, its environment, and its motion through the interstellar medium (ISM). In principle
its mass-loss history can be constrained by comparing hydrodynamic models with
observations. Observations and numerical simulations indicate that Betelgeuse has a very
young bow shock, hence the star may have only recently become a RSG. To test this
possibility we calculated a stellar evolution model for a single star with properties
consistent with Betelgeuse. We incorporated the resulting evolving stellar wind into 2D
hydrodynamic simulations to model a runaway blue supergiant (BSG) undergoing the
transition to a RSG near the end of its life. The collapsing BSG wind bubble induces a bow
shock-shaped inner shell which at least superficially resembles Betelgeuse’s bow shock,
and has a similar mass. Surrounding this is the larger-scale retreating bow shock
generated by the now defunct BSG wind’s interaction with the ISM. We investigate whether
this outer shell could explain the bar feature located (at least in projection) just in
front of Betelgeuse’s bow shock.