wikiHow Solar System Glossary Order of the planets: 1. Mercury 2. Venus 3. Earth 4. Mars 5. Jupiter 6. Saturn 7. Uranus 8. Neptune Note that Pluto used to be considered the ninth planet, but it was reclassified as a dwarf planet in 2006. Terms: * Asteroid: A small, rocky object that orbits the Sun. Most asteroids are located in the asteroid belt between Mars and Jupiter. * Comet: A small, icy object that orbits the Sun. When a comet gets close enough to the Sun, the heat causes its icy surface to vaporize, creating a bright tail. * Dwarf planet: A celestial body that orbits the Sun and is round, but has not cleared its orbit of other debris. Pluto is the most well-known dwarf planet. * Gas giant: A planet that is primarily composed of hydrogen, helium, and other gases. Jupiter, Saturn, Uranus, and Neptune are the four gas giants in our solar system. * Gravity: The force that pulls objects together. In the solar system, the gravity of the Sun keeps the planets and other objects in orbit. * Inner planets: The four planets in our solar system that are closest to the Sun: Mercury, Venus, Earth, and Mars. They are known as the inner planets or terrestrial planets because they are primarily composed of rock and metal. * Jovian planets: Another name for the four gas giant planets in our solar system: Jupiter, Saturn, Uranus, and Neptune. * Kuiper Belt: A region of the solar system beyond Neptune that contains many small, icy objects such as comets and dwarf planets. * Meteor: A small piece of rock or metal that enters the Earth's atmosphere, often burning up due to the friction with the air. Meteors are sometimes called shooting stars. * Outer planets: The four planets in our solar system that are furthest from the Sun: Jupiter, Saturn, Uranus, and Neptune. They are also known as the gas giants. * Planet: A celestial body that orbits the Sun and has enough gravity to become spherical. There are eight planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. * Rocky planets: Another name for the four inner planets in our solar system: Mercury, Venus, Earth, and Mars. They are known as the rocky planets or terrestrial planets because they are primarily composed of rock and metal. * Solar system: The Sun, the planets, and other objects that orbit around it, including comets, asteroids, and other debris. * Terrestrial planets: Another name for the four inner planets in our solar system: Mercury, Venus, Earth, and Mars. They are known as the terrestrial planets or rocky planets because they are primarily composed of rock and metal. Page