Our solar system contains a star (the Sun) and the planets orbiting it.
The planets closest to Earth can be seen at night without a telescope.
Except for Earth, the planets are all named after Roman or Greek gods. For example, reddish Mars is named for the Roman god of war. Fast-moving Mercury is named after the Roman god who was a swift messenger. Uranus is named after the Greek sky god.
No two planets are alike, but some are similar. Mercury, Venus, Mars, and Earth are all rocky planets. Much farther from the Sun are the gaseous giants Jupiter, Saturn, Uranus, and Neptune. They are made mainly of hydrogen and helium.
Pluto was discovered in 1930, and added to the list of planets. For decades, astronomers believed our solar system had nine planets. However, in August 2006, the International Astronomical Union (IAU) made a new definition of the solar system. Now there are eight planets and at least five dwarf planets, including Pluto. The solar system also has tens of thousands of smaller bodies, like comets and most asteroids. But stay tuned! Things could change again.
