Transcript for scene 31 of the video " The Incredible Experience vs Ice Age - part 2" by Rolf Witzsche  

The low surface temperature of Arcturus and Alderbaran

The low surface temperature of Arcturus and Alderbaran is not necessarily typical for large stars. The exception is the star, Rigel, that we find in panel 5. This star is 3 times larger than Arcturus and almost twice as large as Alderbaran. It should be a dim star by its size in comparison with Arcurus and Alderbaran. But it isn't. It is intensively active, though not quite as active as it should be for an active star of its size.