@mammy-blue saidIt's so big that the word "big" is not big enough.
@bunnyknight
Someone told me if you place Betelgeuse in the position of our sun, it would engulf Mercurius, Venus, Earth, our moon, Mars, Neptune and Saturn.
Quite big...
@OmarCayenne
Now the answer seems to be a bit more mundane:
Dust is what dims our favorite star:
https://phys.org/news/2020-03-dimming-betelgeuse-isnt-cold-dusty.html