The Solar System consists of the Sun and those celestial objects bound to it by gravity. These objects are the eight planets (since Pluto is no lonnger classed as a planet) and their 166 known moons; four dwarf planets and their four known moons, and billions of small bodies, including asteroids, Kuiper belt objects, comets, meteoroids, and interplanetary dust.

In broad terms, the charted regions of the Solar System consist of the Sun; four terrestrial inner planets; an asteroid belt composed of small rocky bodies; four gas giant outer planets; a second belt, the Kuiper belt, composed of two icy, dwarf planets and Kuiper belt objects; the scattered disc, composed of the dwarf planet Eris and icy scattered disc objects; the heliopause; and ultimately the hypothetical Oort cloud.

In order of their distances from the Sun, the terrestrial planets are: Mercury, Venus, Earth and Mars.

The outer gas giants (or Jovians) are: Jupiter, Saturn, Uranus and Neptune.

Four objects are classed as dwarf planets as of mid-2008, though the list is expected to grow:

Ceres, the largest object in the asteroid belt;
Pluto, the largest known object in the Kuiper belt;
Makemake, the largest classical Kuiper belt object.
Eris, the largest known object in the scattered disc.

Six of the eight planets and two of the dwarf planets are in turn orbited by natural satellites, usually termed "moons" after Earth's Moon, and each of the outer planets is encircled by planetary rings of dust and other particles. All the planets except Earth are named after deities from Greco-Roman mythology.

Five planets were known in antiquity because all could be observed moving against the background stars with the naked eye. These were: Mercury, Venus, Mars, Jupiter and Saturn. Uranus was discovered telescopically on March 13, 1781 by William and Caroline Herschel. Neptune's orbit was predicted mathematically and it was finally obsevered at the calculated position on September 23, 1846.

Pluto, which was formerly classed as a planet, was discovered telescopically by Clyde Tombaugh in 1930.

Solar System Links

Nine Planets - The Nine Planets provides an overview of the history, mythology, and current scientific knowledge of each of the planets and moons in our solar system. Each page has text and images and some have sounds and movies.

Planetary Photojournal - A huge range of photos of bodies in the Solar System. The site is updated regularly with new images, includling images from ongoing missions.

Solar System - JPL site providing facts and information about the planets and moons in our Solar System along with recent news and things to watch out for.

Solar System Exploration - NASA site providing facts and information about the planets and moons in our Solar System.

Solar System Live - An interactive orrery on the web. Controls allow you to set time and date, viewpoint, observing location, orbital elements to track an asteroid or comet, and a variety of other parameters.

Solar System Simulator - This excellent site allows you to simulate what the solar system looks like, at any time, provides browsable planet maps and artwork, rendered spacecraft models and much more.

Views of the Solar System - Views of the Solar System contains a wealth of information about the Sun, planets, satellites, asteroids, comets and meteoroids.

Welcome to the Planets - This is a collection of many of the best images from NASA's planetary exploration program.