  The light curves (time series of the radiated energy) of most large
amplitude, pulsating stars such as the well known Cepheid stars are regular.
However, a smaller group of variable stars that are located next to them in the
Hertzsprung- Russell diagram undergoes irregular light variations and exhibits
irregular radial velocities as well. The mechanism behind this irregular
behavior was a long standing mystery. A flow reconstruction technique based on
the observed lightcurves of six separate stars shows that their underlying
dynamics is chaotic and low dimensional (d=4). Furthermore, we present evidence
that the physical mechanism behind the behavior is the nonlinear interaction of
just two pulsation eigenmodes. In a generalized Shil'nikov scenario, the
pulsation energy alternates continuously, but irregularly between a lower
frequency mode that is linearly unstable and thus growing, and a stable
overtone that gets entrained through a low order resonance (2:1), but that
wants to decay. The flow reconstruction from the stellar light curve thus
yields interesting physical insight into the pulsation mechanism.
