Which stars are cold?

Cold stars are typically classified as red dwarfs, which are the smallest and least massive type of main-sequence stars. Their surface temperatures range from about 2,500 to 4,000 Kelvin, making them significantly cooler than brighter stars like our Sun. Additionally, brown dwarfs, which are sub-stellar objects that do not undergo hydrogen fusion, are also considered cold, with temperatures below 2,500 Kelvin. These stars are often dim and difficult to observe due to their low temperatures and luminosities.