The solar system consists of:
- The Sun
- Planets and dwarf planets which orbit around the Sun. These are all kept in orbit by the Sun's gravity. The orbits are almost circular, contrary to most diagrams.
- Satellites (moons) which orbit planets, kept in orbit around the planet by the planet's gravity.
- Comets and asteroids which orbit the Sun.
Planets in the Solar System[edit | edit source]
- Earth (only planet known to hold life)
- Jupiter (largest planet in the solar system)
Dwarf Planets[edit | edit source]
These include Pluto, Ceres and Eris. Pluto was originally classified as a planet, but it lost this status following a vote in an worldwide astronomy conference. Pluto's moon "Charon" is so relative in size to Pluto that they actually orbit each other, although only Pluto has been given dwarf planet status.
Ceres, as well as being a dwarf planet, is the largest asteroid. It lies within the asteroid belt between Mars and Jupiter. Pluto orbits further away from the Sun than Neptune, while Eris orbits further out still.
As telescopes and techniques have improved astronomers have discovered more and more distant and smaller objects in our solar system. In the late 20th century several objects were discovered comparable in size to Pluto, e.g. Sedna and Eris. If Pluto was a planet then these objects too should be planets and future objects of similar size. This is why the third statement above was decided upon in 2006. The third statement means that there are no other objects, other than its own satellites, in the region of its orbit. Objects such as Pluto which do not meet condition 3 are referred to as dwarf planets. There are officially 8 planets and 5 dwarf planets in our solar system.