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What does it mean if an exoplanet is 'habitable'?

Published: 13th June, 2020 at 11:00
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Habitable doesn't mean inhabited.

All forms of life that we know of depend on one critical component: liquid water. So, in the search for life, astronomers focus on planets where liquid water could exist, which they call 'habitable'.

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Every star has a 'habitable zone', also called the 'Goldilocks zone', where it is not too hot and not too cold. A planet in the habitable zone gets the right amount of energy from the star to support liquid water. Any closer in to the star and water would boil, and any further out and it would freeze.

However, this doesn't guarantee that liquid water would exist on a planet in the habitable zone. The planet's atmosphere could be too thick, raising the temperature even higher. And even if liquid water does exist on the planet, habitable doesn't mean inhabited.

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Authors

Sara RigbyOnline staff writer, BBC Science Focus

Sara is the online staff writer at BBC Science Focus. She has an MPhys in mathematical physics and loves all things space, dinosaurs and dogs.

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