The surface temperature of an exoplanet in the habitable zone should allow for the existence of liquid water.

The region in space around a star that might potentially support life is known as the habitable zone. Water is one of the key ingredients for life as we know it. Exoplanets in the habitable zone should have surface conditions that allow for the existence of liquid water. These exoplanets would receive enough energy from their local star that their surface temperatures would range between the freezing point of water (273° K or 0° C, 32° F) and the boiling point of water (373° K or 100° C, 212° F). Earth, as seen in the main view panel, is often called the blue planet because of the abundant existence of liquid water on its surface.