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Our solar system consists of a star we call the Sun, the planet Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. It includes: the satellites of the planets; numerous comets, asteroids, and meteoroids. The Sun is the richest source of energy (mostly in the form of heat and light) in the solar system. The whole solar system, together with the local stars visible on a clear night, orbits the center of our home galaxy, a spiral disk of 200 billion stars we call theMilky Way. The Milky Way has two small galaxies orbiting it nearby, which are visible from the southern hemisphere. They are called the Large Magellanic Cloud and the Small Magellanic Cloud. The nearest large galaxy is the Andromeda Galaxy. It is a spiral galaxy like the Milky Way but is 4 times as massive and is 2 million light years away.
The planets, most of the satellites of the planets and the asteroids revolve around the Sun in the same direction, in nearly circular orbits. When looking down from above the Sun's north pole, the planets orbit in a counter-clockwise direction. The planets orbit the Sun in or near the same plane, called the ecliptic.
Composition of the Solar System
The Sun contains 99.85% of all the matter in the Solar System. The planets, which condensed out of the same disk of material that formed the Sun, contain only 0.135% of the mass of the solar system. Jupiter contains more than twice the matter of all the other planets combined. Satellites of the planets, comets, asteroids, meteoroids, and the interplanetary medium constitute the remaining 0.015%. The following table is a list of the mass distribution within our Solar System.
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Mass Distribution |
| Sun |
99.85% |
| Planets |
0.135% |
| Comets |
0.01% |
| Satellites |
0.00005% |
| Minor Planets |
0.0000002% |
| Meteoroids |
0.0000001% |
| Interplanetary Medium |
0.0000001% |
Formation of solar system - movie |
