Illustration of habitable zones, which are also known as Goldilocks zones. This is the area around a star where planets can support liquid water on their surfaces. At top is a cool star, where an orbiting planet must be close to the star to maintain a warm enough temperature for liquid water. At middle is a sun-like star, where an orbiting planet can be further away and still support liquid water in comparison to a cool star. At bottom is a hot star, where an orbiting planet must be far away before liquid water is able to exist.