THE GOLDILOCKS ZONE

DID YOU KNOW?

Special conditions, such as Europa’s subsurface ocean, can allow water to exist outside the habitable zone

In the fairy tale, Goldilocks is a fussy little girl whose porridge has to be just right, neither too hot nor too cold. It’s the same with life itself – or at least the kind of water-based life we’re familiar with on Earth. A planet has to be just right: neither so cold that water only exists as frozen ice, nor so hot that it all boils away. That’s not going to be true of all the planets orbiting a star, just those within a certain range of orbits dubbed the ‘Goldilocks zone’, or more formally the ‘habitable zone’. If a planet’s orbit takes it too close to its parent