A dwarf planet is a planetary-mass object that does not dominate its region of space (as a planet does) and is not a satellite. That is, it is in direct orbit of the Sun and is massive enough to be plastic – for its gravity to maintain it in a hydrostatically equilibrious shape (usually a spheroid) – but has not cleared the neighborhood of its orbit of similar objects.[2] The prototype dwarf planet is Pluto.[3] The interest of dwarf planets to planetary geologists is that, being possibly differentiated and geologically active bodies, they may display planetary geology, an expectation borne out by the 2015 New Horizons mission to Pluto.
The number of dwarf planets in the Solar System is unknown. This is because determining whether a body is in hydrostatic equilibrium requires close observation by spacecraft. The half-dozen largest candidates have either been visited by spacecraft (Pluto and Ceres) or have at least one known moon (Pluto, Eris, Haumea, Makemake, Gonggong, Quaoar), which allows their masses and thus an estimate of their densities to be determined. Mass and density in turn can be fit into models of hydrostatic equilibrium.
The term dwarf planet was coined by planetary scientist Alan Stern as part of a three-way categorization of planetary-mass objects in the Solar System: classical planets (the big eight), dwarf planets and satellite planets. Dwarf planets were thus conceived of as a category of planet, as the name suggests. However, in 2006 the term was adopted by the International Astronomical Union (IAU) as a category of sub-planetary objects, part of a three-way recategorization of bodies orbiting the Sun.[2] The decision had been precipitated by the discovery of Eris, an object farther away from the Sun than Neptune that was more massive than Pluto but still much smaller than the classical planets, after discoveries of a number of other objects that rivaled Pluto in size had forced a reconsideration of what Pluto was.[4] Thus Stern and many other planetary geologists distinguish dwarf planets from classical planets, but since 2006 the IAU and the majority of astronomers have excluded bodies such as Eris and Pluto from the roster of planets altogether. is a planetary-mass item that doesn't overwhelm its area of room (as a planet does) and is certainly not a satellite. That is, it is in direct circle of the Sun and is sufficiently monstrous to be plastic – for its gravity to keep up it's anything but a hydrostatically equilibrious shape (typically a spheroid) – however has not gotten the local free from its circle of comparable objects.[2] The model bantam planet is Pluto.[3] The interest of bantam planets to planetary geologists is that, being potentially separated and geographically dynamic bodies, they may show planetary topography, an assumption borne out by the 2015 New Skylines mission to Pluto.
The quantity of bantam planets in the Nearby planetary group is obscure. This is on the grounds that deciding if a body is in hydrostatic balance requires close perception by space apparatus. The about six biggest competitors have either been visited by space apparatus (Pluto and Ceres) or have at any rate one known moon (Pluto, Eris, Haumea, Makemake, Gonggong, Quaoar), which permits their masses and in this manner a gauge of their densities to be resolved. Mass and thickness thus can be found a way into models of hydrostatic harmony.
The term bantam planet was instituted via planetary researcher Alan Harsh as a feature of a three-path order of planetary-mass items in the Nearby planetary group: traditional planets (the large eight), bantam planets and satellite planets. Bantam planets were consequently considered as a class of planet, as the name proposes. Nonetheless, in 2006 the term was embraced by the Global Cosmic Association (IAU) as a classification of sub-planetary items, part of a three-route recategorization of bodies circling the Sun.[2] The choice had been encouraged by the revelation of Eris, an article farther away from the Sun than Neptune that was more gigantic than Pluto yet a lot more modest than the traditional planets, after disclosures of various different items that equaled Pluto in size had constrained a reexamination of what Pluto was.[4] Along these lines Harsh and numerous other planetary geologists recognize bantam planets from old style planets, yet since 2006 the IAU and most of cosmologists have avoided bodies like Eris and Pluto from the program of planets out and out.
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