What are Goldilocks Zone ?

Goldilocks Zone refers to a habitable zone where the temperature is neither too high nor too low. In September 2010, a US team announced that it had discovered the planet Gliese 581g orbiting a star some 20 light-years away. Gliese 581g has a mass about three to four times that of Earth, but it orbits in the so-called “Goldilocks zone” – a region around its host star where temperatures are neither too hot nor too cold. Such conditions could allow for the presence on the planet’s surface of liquid water – a key ingredient for life.