These "cool" stars are actually star failures. They are referred to by astronomers as brown dwarfs.
Due to their low temperatures, they are much more difficult to spot in the night sky. In fact, NASA astronomers were only able to view them using a special infrared telescope, Spitzer.
Spitzer is great at looking for brown stars in a specific spot, but the Wide-Field Infrared Survey Explorer (WISE) mission is now being used to scan the entire sky for these elusive orbs.
Who knows how many new stars are going to pop up!