The stars that are considered the coolest are typically classified as red dwarfs. The most notable among them is a star known as Proxima Centauri, which is the closest known star to the Sun. Red dwarfs have surface temperatures of less than 3,500 Kelvin, making them significantly cooler than many other types of stars like our Sun.
Red dwarfs are fascinating not only because of their low temperatures but also because of their longevity. They can burn for billions of years, far longer than larger stars, leading to a stable environment for potential planets orbiting them. Many astronomers believe that these cooler stars could host habitable exoplanets, which adds to their interest in the field of astrobiology.