  Critical transitions occur in complex dynamical systems, when the system
dynamics undergoes a regime shift. These can often occur with little change in
the mean amplitude of system response prior to the actual time of transition.
The recent dimming and brightening event in Betelgeuse occured as a sudden
shift in the brightness and has been the subject of much debate. Internal
changes or an external dust cloud have been suggested as reasons for this
change in variability. We examine whether the dimming and brightening event of
2019-20 could be due to a critical transition in the pulsation dynamics of
Betelgeuse, by studying the characteristics of the light curve prior to
transition. We calculate the quantifiers hypothesised to rise prior to a
critical transition for the light curve of Betelgeuse upto the dimming event of
2019-20. These include the autocorrelation at lag-1, variance and the spectral
coefficient calculated from detrended fluctation analysis (DFA), apart from two
measures that quantify the recurrence properties of the light curve.
Significant rises are confirmed using the Mann-Kendall trend test. We see a
significant increase in all quantifiers (p < 0.05) prior to the dimming event
of 2019-20. This suggests that the event was a critical transition related to
the underlying nonlinear dynamics of the star. Together with results that
suggests minimal change in $T_{eff}$ and infra-red flux, a critical transition
in the pulsation dynamics could be a possible reason for the unprecedented
dimming of Betelgeuse. The rise in the studied quantifiers prior to the dimming
event, supports this possibility.
