Life Elsewhere
Astrobiologists believe that three ingredients which are vital for life. They are water, energy, and organic molecules such as carbon (C). Energy and organic molecules are abundant in the Universe. But liquid water is rare.
- The Habitable Zone (HZ)
A habitable zone (HZ) is the area around a star where liquid water could exist on or near the surface of a planet. We call it an HZ because we believe liquid water is vital for the existence of life.
An HZ is sometimes called a CHZ, where the C stands for 'continuously' or 'circumstellar'. The name Goldilocks Zone is perhaps a more useful way to describe an HZ. It is a region that is not too hot, and not too cold, but just right! The size and location of an HZ depend on the size and type of the star.