Why it looks red
Antares has a cool outer atmosphere compared with the Sun. That lower temperature shifts its visible color toward red-orange.
Its enormous radius makes it highly luminous despite the cool surface.
A real measured atmosphere
Modern observations have mapped motion in Antares' atmosphere, showing that the outer layers of red supergiants are dynamic rather than simple smooth spheres.
This makes Antares valuable for understanding mass loss before supernova.
How it compares
Antares is often discussed alongside Betelgeuse. Both are red supergiants, variable, and large enough to make solar-system scale comparisons meaningful.