Planets

thumb|upright=1.5|The eight planets of the Solar System with size to scale (up to down, left to right): [[Saturn, Jupiter, Uranus, Neptune (outer planets), Earth, Venus, Mars, and Mercury (inner planets)]] A planet is a large, rounded astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets by the most restrictive definition of the term: the terrestrial planets Mercury, Venus, Earth, and Mars, and the giant planets Jupiter, Saturn, Uranus, and Neptune. The best available theory of plane

thumb|300px|right|Debris disks detected in HST archival images of young stars, HD 141943 and HD 191089, using improved imaging processes (24 April 2014). thumb|486958 Arrokoth, the first pristine planetesimal visited by a spacecraft.

discredited hypothesis about Solar System planets' orbits

astronomical theory that the Solar System formed from nebulous material

any celestial object massive enough to achieve hydrostatic equilibrium, but not enough to sustain core fusion like a star

history and evolution of the term planet

definition of a planet as a body orbiting the Sun, in hydrostatic equilibrium, having cleared the neighborhood around its orbit; ratified by the IAU in August 2006, thereby reclassifying Pluto as a dwarf planet instead

astronomical object with insufficient mass to sustain nuclear fusion

outward bulge around a planet's equator due to its rotation

Wikimedia list article

area of study

moons comparable in size to small planets