A planet according to modern philosophy is a large object such as Jupiter or Earth that orbits a star. It is smaller than a star, and it does not make light. Planets are ball-shaped (spheres). Objects that orbit planets are called moons. There are eight planets in the Solar System. Pluto used to be known as a planet, but in August 2006, the International Astronomical Union decided it was a dwarf planet instead. There are four more known dwarf planets in the Solar System, Ceres, Makemake, Eris and Haumea.
The name "planet" is from the Greek word πλανήτης (planetes), meaning "wanderers", or "things that move". Until the 1990s, people only knew of those in the Solar System. As of June 2011, we know of 563 other planets.[1] All of these newly found planets are orbiting other stars: they are extrasolar planets. Sometimes people call them "exoplanets".
The name "planet" is from the Greek word πλανήτης (planetes), meaning "wanderers", or "things that move". Until the 1990s, people only knew of those in the Solar System. As of June 2011, we know of 563 other planets.[1] All of these newly found planets are orbiting other stars: they are extrasolar planets. Sometimes people call them "exoplanets".
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