Red supergiants are massive stars that have exhausted the hydrogen in their cores and expanded significantly. They are among the largest stars in the universe, with diameters up to 1,500 times that of the Sun. Their surface temperatures are relatively low, typically ranging from 3,000 to 4,000 Kelvin, giving them a reddish appearance. These stars are short-lived compared to smaller stars, lasting only a few million years before they end their life cycle in a spectacular explosion known as a supernova. Famous examples of red supergiants include Betelgeuse and Antares, which are visible to the naked eye from Earth.