For the ancient Greeks (before the age of telescopes) the night sky was thought to consist of two very similar components: fixed stars, which remained motionless in relation to each other, and "wandering stars" (Ancient Greek: asteres planet-ai), which moved relative to the fixed stars over the course of the year.

This group comprised the five planets visible to the naked eye (Mercury, Venus, Mars, Jupiter, Saturn) and latterly broadened to include the Sun and the Moon, making a total of seven planets.

After the invention of telescopes another 3 planets were identified (Unanus, Neptune, Pluto)