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, often hundreds of times larger than the Sun. Their surface temperatures are relatively low, typically between 3,000 and 4,000 degrees Celsius, giving them a reddish appearance. These stars are short-lived, usually existing for 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 and serve as important objects of study in astronomy.