Solar System - The solar system comprises the Sun and the retinue of celestial objects gravitationally bound to it: the eight planets, their 162 known moons, three currently identified solar system dwarf planets and their four known moons, and thousands of small bodies. This last category includes asteroids, meteoroids, comets, and interplanetary dust.

In broad terms, the charted regions of the Solar System consist of the Sun, four rocky bodies close to it called the terrestrial planets, an inner belt of rocky asteroids, four gas giant planets and an outer belt of small icy bodies known as the Kuiper belt. In order of their distances from the Sun, the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Six of the eight planets are in turn orbited by natural satellites (usually termed "moons" after Earth's Moon) and every planet past the asteroid belt is encircled by planetary rings of dust and other particles. The planets other than Earth are named after gods and goddesses from Greco-Roman mythology.

From 1930 to 2006, Pluto, the largest known Kuiper belt object, was considered the Solar System's ninth planet. However, in 2006 the International Astronomical Union (IAU) created an official definition of the term "planet". Under this definition, Pluto is reclassified as a dwarf planet, and there are eight planets in the Solar System. In addition to Pluto, the IAU currently recognizes two other dwarf planets: Ceres, the largest object in the asteroid belt, and Eris, which lies beyond the Kuiper belt in a region called the scattered disc. Of the known dwarf planets, only Ceres has no moons.

For many years, the Solar System was the only known example of planets in orbit around a star. The discovery in recent years of many extrasolar planets has led to the term "solar system" being applied generically to all the newly discovered systems. Technically, however, it should strictly refer to Earth's system only, as the word "solar" is derived from the Sun's Latin name, Sol. Other such systems are usually referred to by the names of their parent star; e.g. "the Alpha Centauri system" or "the 51 Pegasi system".