We have taken pictures of sunspots on Betelgeuse!
Of course, the star doesn’t look like the illustration here but that is the picture of the sunspots (just over-layed onto the art). The images were taken in infrared by the IOTA interferometer in Arizona and you can see how big the sunspots are compared to the star itself. When you compare that to our puny solar system you can start to understand how large the star actually is. Just one of the spots is the distance Earth is from the Sun! The full illustration of Betelgeuse by ESO shows a huge plume of gas being ejected from Betelgeuse that reaches out to the orbit of Neptune. The star is losing a lot of material and is shrouded in these plums and it is contracting and expanding as it gives its last breaths. So measuring the exact size is difficult. But one thing is for sure, it is on the verge of exploding, but “on the verge” in stellar time scales means it will go supernova sometime within the next million years or so.
We have seen another star with huge sunspots as well, HD 12545. Source: Astronomy Now