The seven classical planets (the Sun, the Moon, Mercury, Venus, Mars, Jupiter and Saturn), are the visible wandering lights of the sky, and they form the backbone of Western astrology, magic and alchemy. Each carries a wide web of correspondences: a metal, a day of the week, a set of deities, a temperament, a range of affairs it governs, and, in magic, a spirit, an intelligence and a magic square.
To the ancient and medieval mind these seven were the planets; the Sun and Moon were counted among them as "lights", and the outer planets Uranus, Neptune and Pluto, discovered from 1781 onward, are modern additions that later astrology incorporates but the classical scheme does not include.