What Is the Habitable Zone?

Earth is habitable due to the right conditions and ingredients, with water being one of the most critical factors. The ability to have liquid water is considered essential for life on exoplanets as well.

Astronomers use the concept of the 'habitable zone' to identify areas around a star where a rocky planet with an atmosphere could have liquid water on its surface. In our solar system, this zone extends from Venus to Mars, with Earth comfortably in the middle.

Simply being in the habitable zone does not guarantee a planet is habitable; the Moon, for instance, shares Earth's orbit but is not habitable. The size and brightness of a star influence the location and size of its habitable zone.

Proxima Centauri, a smaller and dimmer star than our sun, has a much smaller and closer habitable zone. While every star has a habitable zone, not all have planets within it, as seen with Kepler-90 where planets are too close to the star. The ongoing search aims to find other water-covered planets in their own habitable zones.