It is a bright star of the red supergiant type, it isn't a supernova. It is the ninth brightest star in the sky and his characteristic color comes from the low temperatures of its surface.
What's happening to Betelgeuse?
It's brightness has fallen three times, reaching levels never seen in the last 150 years. It is not strange that its brightness changes, because it is what is known as a semi-variable star, in which the luminosity rises and falls almost periodically, but has never undergone such a drastic change.
Betelgeuse is in the last phase of its life and destined to explode in a supernova sometime between now and the next 100,000 years. It has increased in size due to changes in the nuclear fusion process at its center. The star is so large that if it were to replace the Sun in our Solar System, its outer surface would reach beyond the orbit of Jupiter.