  We present optical spectrophotometry of the red supergiant Betelgeuse from
2020 February 15, during its recent unprecedented dimming episode. By comparing
this spectrum to stellar atmosphere models for cool supergiants, as well as
spectrophotometry of other Milky Way red supergiants, we conclude that
Betelgeuse has a current effective temperature of 3600 +/- 25 K. While this is
slightly cooler than previous measurements taken prior to Betelgeuse's recent
lightcurve evolution, this drop in effective temperature is insufficient to
explain Betelgeuse's recent optical dimming. We propose that episodic mass loss
and an increase in the amount of large-grain circumstellar dust along our
sightline to Betelgeuse is the most likely explanation for its recent
photometric evolution.
