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The defining dynamic characteristic of a planet, according to the IAU definition, is that it has cleared its neighborhood. A planet that has cleared its neighborhood has accumulated enough mass to gather up or sweep away all the planetesimals in its orbit. In effect, it orbits its star in isolation, as opposed to sharing its orbit with a ...
The definition of the term planet has changed several times since the word was coined by the ancient Greeks. Greek astronomers employed the term ἀστέρες πλανῆται (asteres planetai), 'wandering stars', for star-like objects which apparently moved over the sky.
A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet. This definition would have led to three more celestial bodies being recognized as ...
A planet in the Solar System that have orbits smaller than the asteroid belt. [nb 2] Mercury, Venus, Earth, Mars: Outer planet: A planet in the Solar System beyond the asteroid belt, and hence refers to the gas giants. Jupiter, Saturn, Uranus and Neptune Pulsar planet: A planet that orbits a pulsar or a rapidly rotating neutron star. PSR B1257 ...
The geophysical definition of a planet put forth by Stern and Levinson is an alternative to the IAU's definition of what is and is not a planet and is meant to stand as the geophysical definition, while the IAU definition, they argue, is intended more for astronomers. Nonetheless, some geologists favor the IAU's definition.
These are lists of planets.A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a young protostar orbited by a protoplanetary disk.
The term dwarf planet was coined by planetary scientist Alan Stern [citation needed] as part of a three-way categorization of planetary-mass objects in the Solar System: classical planets, dwarf planets, and satellite planets, following the new definition of planet proposed by uruguayan astronomers Julio Ángel Fernández and Gonzalo Tancredi ...
A terrestrial planet, tellurian planet, telluric planet, or rocky planet, is a planet that is composed primarily of silicate, rocks or metals. Within the Solar System , the terrestrial planets accepted by the IAU are the inner planets closest to the Sun : Mercury , Venus , Earth and Mars .