Planet - Within our solar system

A planet is generally considered to be a relatively large mass of accreted matter in orbit around a star that is not a star itself. The name comes from the Greek term πλανήτης, planētēs, meaning "wanderer", as ancient astronomers noted how certain lights moved across the sky in relation to the other stars. Based on historical consensus, the International Astronomical Union (IAU) lists nine planets in our solar system. Since the term "planet" has no precise scientific definition, however, many astronomers contest that ...

Including:

• Planet - Planetary formation
• Planet - Within our solar system
• Planet - Accepted planets
• Planet - Other candidates
• Planet - Extrasolar planets
• Planet - Brown dwarf planets
• Planet - Interstellar planets
• Planet - Definition and classification of planets
• Planet - Suggested wide definitions
• Planet - Suggested narrow definitions
• Planet - Further classification

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Main article: Solar system The process of naming planets and their features is known as planetary nomenclature. All the currently accepted planets in the solar system are named after Roman gods, except for Uranus (named after a Greek god) and the Earth, which was not seen as a planet by the ancients but rather the centre of the universe. The original number of planets was seven: Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn. These were all seen as regular "wanderers" in the sky. Developments in Astronomy removed the Sun and the Moon, and added the current ...

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Planet, Planet - Planetary formation, Planet - Within our solar system, Planet - Accepted planets, Planet - Other candidates, Planet - Extrasolar planets, Planet - Brown dwarf planets, Planet - Interstellar planets, Planet - Definition and classification of planets, Planet - Suggested wide definitions, Planet - Suggested narrow definitions, Planet - Further classification

Read more here: » Planet: Encyclopedia II - Planet - Within our solar system

Much like "continent", "planet" is a word without a precise definition, with history and culture playing as much of a role as geology and astrophysics. Recent definitions have been vague and imprecise; The American Heritage Dictionary, for instance, formerly defined a planet as: A nonluminous celestial body larger than an asteroid or comet, illuminated by light from a star, such as the Sun, around which it revolves. In the solar system there are nine known planets: Mercury, Venus, Ea ...

See also:

Planet, Planet - Planetary formation, Planet - Within our solar system, Planet - Accepted planets, Planet - Other candidates, Planet - Extrasolar planets, Planet - Brown dwarf planets, Planet - Interstellar planets, Planet - Definition and classification of planets, Planet - Suggested wide definitions, Planet - Suggested narrow definitions, Planet - Further classification

Read more here: » Planet: Encyclopedia II - Planet - Definition and classification of planets

It is not known with certainty how planets are formed. The prevailing theory is that they are formed from those remnants of a nebula that don't condense under gravity to form a protostar. Instead, these remnants become a thin disc of dust and gas revolving around the protostar and begin to condense about local concentrations of mass within the disc. These concentrations become ever more dense until they collapse inward under gravity to form protoplanets. When the protostar has grown such that it ignites to form a star, its solar wind blows a ...

See also:

Planet, Planet - Planetary formation, Planet - Within our solar system, Planet - Accepted planets, Planet - Other candidates, Planet - Extrasolar planets, Planet - Brown dwarf planets, Planet - Interstellar planets, Planet - Definition and classification of planets, Planet - Suggested wide definitions, Planet - Suggested narrow definitions, Planet - Further classification

Read more here: » Planet: Encyclopedia II - Planet - Planetary formation

Of the 173 extrasolar planets (those outside our solar system) discovered to date (October 2005) most have masses which are about the same or larger than Jupiter's. Exceptions include a number of planets discovered orbiting burned-out star remnants called pulsars, such as PSR B1257+12, the planets orbiting the stars Mu Arae, 55 Cancri and GJ 436 which are approximately Neptune-sized [1], and a planet orbiting Glies ...

See also:

Planet, Planet - Planetary formation, Planet - Within our solar system, Planet - Accepted planets, Planet - Other candidates, Planet - Extrasolar planets, Planet - Brown dwarf planets, Planet - Interstellar planets, Planet - Definition and classification of planets, Planet - Suggested wide definitions, Planet - Suggested narrow definitions, Planet - Further classification

Read more here: » Planet: Encyclopedia II - Planet - Extrasolar planets