<P> In astronomy and astrobiology, the circumstellar habitable zone (CHZ), or simply the habitable zone, is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure . The bounds of the CHZ are based on Earth's position in the Solar System and the amount of radiant energy it receives from the Sun . Due to the importance of liquid water to Earth's biosphere, the nature of the CHZ and the objects within it may be instrumental in determining the scope and distribution of Earth - like extraterrestrial life and intelligence . </P> <P> The habitable zone is also called the Goldilocks zone, a metaphor of the children's fairy tale of "Goldilocks and the Three Bears", in which a little girl chooses from sets of three items, ignoring the ones that are too extreme (large or small, hot or cold, etc .), and settling on the one in the middle, which is "just right". </P>

The habitable zone is the region around a star where