A classical planet is a celestial body that:
A dwarf planet is a celestial body that:
All objects orbiting the Sun that are not classical planets or dwarf planets are referred to collectively as "small Solar System bodies". These currently include most of the Solar System asteroids, most trans-Neptunian objects (TNOs), comets, and other small bodies.
Other potential dwarf planetsAmong other Kuiper Belt objects with claims to possible dwarf planethood are
Other ways of categorizing planetsBy composition the classical planets can be divided into terrestrial, or rocky, planets (Mercury, Venus, Earth, and Mars), which are made primarily of rock and metal and have relatively high densities, slow rotation, and solid surfaces, and jovian planets, or gas giants, (Jupiter, Saturn, Uranus, and Neptune), which are composed mostly of hydrogen and helium and generally have low densities, rapid rotation, and deep atmospheres. By size, the planets Mercury, Venus, Earth, and Mars, all with diameters less than 13,000 km, are described as small, while Jupiter, Saturn, Uranus, and Neptune, all with diameters greater than 48,000 km, are said to be giant. By position relative to the Sun, there are the inner planets (Mercury, Venus, Earth, and Mars) and the outer planets (Jupiter, Saturn, Uranus, and Neptune), with the asteroid belt marking the boundary between the inner and outer Solar System. By position relative to Earth, Mercury and Venus are described as inferior planets, whereas all planets beyond and including Mars are said to be superior.
Extrasolar planetsA large number of planets have also been found orbiting stars other than the Sun. The criteria adopted by astronomers in 2006 to distinguish between classical planets, dwarf planets, and smaller objects was not intended to be applied to these extrasolar planets. There is an additional complication in determining whether some massive companion objects are planets or brown dwarfs (the least massive kind of star).
Related categories PLANETS AND MOONS
EXTRASOLAR PLANETS AND SUBSTELLAR OBJECTS
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