Description GALAXY PLANET WPP HD

A planet is a large astronomical body that is not a star or stellar remnant. There are competing scientific definitions of a 'planet'. In the dynamicist definition adopted by the International Astronomical Union (IAU), a planet is a non-stellar body that is massive enough to be rounded by its own gravity, that directly orbits a star, and that has cleared its orbital zone of competing objects. The IAU has also declared that there are eight planets in the Solar System, independently of the formal definition.[b][1][2] In the geological definition used by most planetologists, a planet is a geologically active sub-stellar body, possibly a satellite. In addition to the eight Solar planets accepted by the IAU, these include dwarf planets such as Eris and Pluto and planetary-mass moons.[3]
The term planet is ancient, with ties to history, astrology, science, mythology and religion. Apart from the Moon, five planets are visible to the naked eye in the night sky. Planets were regarded by many early cultures as emissaries of deities or as divine themselves. As scientific knowledge advanced, human perception of the planets changed, and the invention of the telescope enabled the discovery of additional planetary objects that were diverse in size, shape and orbit. In 2006, the IAU adopted a resolution limiting the number of planets within the Solar System, though they are not followed by all astronomers, especially planetologists. The IAU resolution is controversial because it excludes many geologically active objects of planetary mass due to where or what they orbit.

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