Illustration of a possible Earth-like planet, with three orbiting moons. This planet is in its star’s habitable zone, neither too hot (like the orange planet), nor too cold (like the blue planet). A star’s habitable zone is a narrow region where liquid water can exist to support life. It depends on the temperature drop with distance from the star, but it also changes with planetary properties such as the atmospheric composition and pressure, and albedo (reflectance).