The star with the lowest surface temperature is Proxima Centauri, a red dwarf star in the Alpha Centauri system. It has a surface temperature of around 2,700 Kelvin (4,840 degrees Fahrenheit).

For comparison, our sun has a surface temperature of about 5,500 Kelvin (9,932 degrees Fahrenheit). Red dwarfs are the coolest, dimmest, and smallest stars.