The distance between a planet and its star is a key concept in astronomy, as it determines how much energy and light the planet receives. This distance is usually measured as an average, since planets move in elliptical orbits and their separation from the star can change slightly over time.

Astronomers often use astronomical units (AU) to describe this distance. One AU is the average distance from the Earth to the Sun, about 150 million kilometers. For example, Mars is about 1.5 AU from the Sun, which is why it receives less sunlight and is colder than Earth. The orbital distance not only affects temperature, but also plays a role in whether a planet could potentially support life, as it influences the presence of liquid water and the planet's climate. Understanding orbital distances helps scientists study exoplanets and search for habitable worlds beyond our solar system.