the.com/habitable zone
the cosmic goldilocks lane where a planet's water stays liquid instead of ice or steam.
means the orbital distance from a star where a planet's surface temperature could allow liquid water to exist.
from coined mid-20th century by astronomers like Su-Shu Huang, later popularized as the goldilocks zone once Earth-water-life logic went mainstream.
venus problemtoo close, water boiled away billions of years ago
mars problemtoo far, water froze into ice caps
zone shiftshabitable zone moves outward as stars age and brighten
not sufficientbeing in zone doesn't guarantee actual habitability