The region around a star where liquid water could potentially exist on a planet's surface, also known as the Goldilocks zone. This zone is neither too hot nor too cold for water to remain liquid under typical atmospheric conditions.
The term evolved from astrobiology in the mid-20th century, combining 'habitable' from Latin 'habitabilis' meaning 'fit to live in' and 'zone' from Greek 'zone' meaning 'belt.' The concept gained prominence with the search for extraterrestrial life.
Earth sits perfectly in the Sun's habitable zone, but this zone is dynamic - as stars age and brighten, the habitable zone moves outward! In about a billion years, Earth will be too hot for liquid water, but Mars might become habitable as it enters the zone.
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