In astronomy, the habitable zone, is the region of space where conditions are best for life to form as we know it on Earth. Planets in these areas are the most likely to have extraterrestrial life. The habitable zone is also called the "life zone", "green belt", "comfort zone" or "Goldilocks zone". One in five stars have an Earth-sized planet in the habitable zone.
In astrobiology, the "Goldilocks zone" refers to the habitable zone around a star. A planet must not be too far away from, or too close to a star to support life. Either extreme would prevent a planet from evolving life. Such a planet is colloquially called a "Goldilocks planet". The best example of a Goldilocks Planet is our Earth.
The "Goldilocks" name is a metaphor for the fairy tale "The Three Bears" in which a little girl named Goldilocks liked everything just right. Her porridge couldn't be too hot or too cold. And her bed couldn't be too hard or too soft. On Earth, everything is just right for living things. It's warm, but not too warm. And it has water, but not too much water.