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Mercury	Venus	Earth	Mars	Jupiter
Saturn	Uranus	Neptune	Pluto	Small Bodies

    Our solar system consists of a star we call the Sun, the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. It also includes the Small Bodies or Satellites of the planets, comets, asteroids, and meteoroids. The Sun is the source of electromagnetic energy (mostly in the form of heat and light) in the solar system.  The solar system, together with stars visible on a clear night, orbits the center of our galaxy, a spiral disk of 200 billion stars we call the Milky Way. 

    The planets 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 four planets closest to the Sun - Mercury, Venus, Earth, and Mars - are called the terrestrial planets because they have solid rocky surfaces. The four large planets beyond the orbit of Mars - Jupiter, Saturn, Uranus, and Neptune - are called gas giants. Tiny, distant, Pluto has a solid but icier surface than the terrestrial planets.

     Nearly every planet - and some of the moons - has an atmosphere. Earth's atmosphere is primarily nitrogen and oxygen. Venus has a thick atmosphere of carbon dioxide, with traces of poisonous gases such as sulfur dioxide. Mars' carbon dioxide atmosphere is extremely thin. Jupiter, Saturn, Uranus, and Neptune are primarily hydrogen and helium. When Pluto is near the Sun, it has a thin atmosphere, but when Pluto travels to the outer regions of its orbit, the atmosphere freezes and "collapses" to the planet's surface. In this regard, Pluto acts like a comet.

    There are more than 100 natural satellites (also called moons) around the various planets in our solar system, ranging from bodies larger than our own Moon to small pieces of debris. Many of these were discovered by planetary spacecraft. Some of these have atmospheres (Saturn's Titan); some even have magnetic fields. Jupiter's moon Io is the most volcanically active body in the solar system. An ocean may lie beneath the frozen crust of Jupiter's moon Europa. Some planetary moons may actually be asteroids that were captured by a planet's gravity. 

    Most of the planets also have magnetic fields which extend into space and form a "magnetosphere" around each planet. These magnetospheres rotate with the planet, sweeping charged particles with them. The Sun has a magnetic field, the heliosphere, which envelops our entire solar system.

Here are some related links

• All about the Sun
• Other Solar Systems
• View A Free Nebula Slide Show
• See How Big the Planets and Moons Are
• Orbits and Physical Characteristics of the Planets

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