Solar System

Our Solar System includes the Sun and all the objects in orbit around the sun. Objects orbiting the sun include planets, moons, asteroids, and comets.

Planets

A planet is defined as an object that orbits the sun, is massive enough that its own gravity pulls it into a nearly round shape, and is dominant enough to clear away objects in its neighborhood. There are 8 planets in the solar system. They are, in order of increasing distance from the sun:

• Mercury
• Venus
• Earth
• Mars
• Jupiter
• Saturn
• Uranus
• Neptune

The first four planets are terrestrial planets, the last 4 planets are jovian planets. Terrestrial planets are small in size, have high densities, and consist of rocky materials. Jovian planets are large in size, have low densities, and consist of gaseous materials.

Dwarf Planets

A dwarf planet is an object that orbits the sun and has a round shape. The crucial difference between a planet and a dwarf planet is that a dwarf planet is not large enough to clear the neighborhood of its orbit. Currently recognized dwarf planets are:

• Pluto^[1]
• Eris
• Ceres

Note

^[1]Pluto was considered a planet until 2006.

Asteroids

Asteroids are irregularly shaped chunks of rocks in the solar system. They exist mostly in 2 places:

• The asteroid belt, which is between the orbits of Mars and Jupiter
• The Kuiper belt, which shares its orbit with Pluto

Comets

Comets are chunks of dust and ice. Some are in an elliptical orbit around the sun, meaning that they will return someday. Some are in a hyperbolic orbit around the sun, meaning that they will only come into the solar system once and will never return.

External links

• Glossary