The Solar System: The Sun and the celestial bodies such as planets, comets, asteroids and meteors which revolve around the Sun form the solar system. The Sun is the nearest star which is the primary source of heat and light for all the planets. The planets do not emit light from their own like stars. Our solar system consists of our star, the Sun, and everything bound to it by gravity, the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune, dwarf planets such as Pluto, dozens of moons and millions of asteroids, comets and meteoroids. The Sun is by far an essential feature of the Solar System, containing about 99.8% of its entire mass. It is the Sun's strong gravitational attraction that 'holds' the Solar System together and keeps all the planets in elliptical orbits around it.