Circumstellar habitable zone
![An example of a system based on stellar luminosity for predicting the location of the habitable zone around various types of stars. Planet sizes, star sizes, orbit lengths, and habitable zone sizes are not to scale.](/Images/godic/202501/06/Habitable_zone_-_HZ1717.png")
![The range of published estimates for the extent of the Sun's CHZ. The conservative CHZ[22] is indicated by a dark-green band crossing the inner edge of the aphelion of Venus, whereas an extended CHZ,[28] extending to the orbit of the dwarf planet Ceres, is indicated by a light-green band.](/Images/godic/202501/06/Estimated_extent_of_the_Solar_Systems_habitable_zone1717.png")
![A video explaining the significance of the 2011 discovery of a planet in the circumbinary habitable zone of Kepler-47.](/Images/godic/202501/06/-Circling_Two_Suns.ogv1717.jpg")
![Natural defenses against space weather, such as the magnetosphere depicted in this artistic rendition, may be required for planets to sustain surface water for prolonged periods.](/Images/godic/202501/06/Magnetosphere_rendition1717.jpg")
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 calculated using the known requirements of Earth's biosphere, its position in the Solar System and the amount of radiant energy it receives from the Sun. Due to the importance of liquid water to life as it exists on Earth, the nature of the CHZ and the objects within is thought to be instrumental in determining the scope and distribution of Earth-like extraterrestrial life and intelligence.