What is a habitable zone?

The term habitable zone is a term frequently used in exoplanet research. In order to form life styles similar to those on Earth on an exoplanet, the entire orbit of the planet must remain in the region suitable for life.

The habitable zone is generally defined as the region with conditions suitable for the presence of liquid water on the surface of a planet. The reason for this is that the presence of liquid water is indispensable for living life. It is possible for various forms of life to form in liquids other than water. However, since water is the most abundant liquid in space, research focuses on water in order to determine whether there is a life outside of the world.

The distance and size of the region that is suitable for life around a star varies according to the characteristics of both the star and the planet. For example, the closer the planet is to the star, the more light it will be exposed to and warmed. Therefore, the planet must be neither too close nor far from the star in order to have liquid water on the surface of the planet. In addition, it is also important whether the planet has an atmosphere and how much greenhouse gases there are in its atmosphere. Even if it is too far from an exoplanet star, greenhouse gases can cause the exoplanet's atmosphere to heat up and have favorable living conditions.