Habitable Zones

This simulation shows how the habitable zone varies as you go from one type of star to another. The habitable zone is the region between the two red circles. Theoretically, a planet in this location could have liquid water on its surface, which is generally considered an important component for the development of life. The orbits of the planets in the solar system are shown as blue circles. Pluto is not included.

Luminosity is the factor that controls the size of the habitable zone the most. For the Main Sequence and White Dwarf stars, as you vary the temperature scale on the bottom, you'll also vary the luminosity and the size of the habitable zone. For the red giants and supergiants, a single luminosity value is used, so temperature isn't a factor in determining the size of the habitable zone for those stars.

When the lines that represent the habitable zone get close to the lines that represent the planetary orbits, the lines look like they are purple - which is what you expect when you combine red and blue, right?