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A number of bodies physically resemble dwarf planets. These include former dwarf planets, which may still have equilibrium shape or evidence of active geology; planetary-mass moons, which meet the physical but not the orbital definition for dwarf planet; and Charon in the Pluto–Charon system, which is arguably a binary dwarf planet.
The geography of Pluto refers to the study and mapping of physical features across the dwarf planet Pluto. On 14 July 2015, the New Horizons spacecraft became the first spacecraft to fly by Pluto. [ 1 ] [ 2 ] During its brief flyby, New Horizons made detailed geographical measurements and observations of Pluto and its moons .
For the giant planets, the "radius" is defined as the distance from the center at which the atmosphere reaches 1 bar of atmospheric pressure. [ 11 ] Because Sedna and 2002 MS 4 have no known moons, directly determining their mass is impossible without sending a probe (estimated to be from 1.7x10 21 to 6.1×10 21 kg for Sedna [ 12 ] ).
Stern's 2018 definition, but not his 2002 definition, excludes the first clause of the IAU definition (that a planet be in orbit around a star) and the third clause (that a planet has cleared the neighborhood around its orbit). It thus counts dwarf planets and planetary-mass moons as planets.
The geology of the dwarf planet, Ceres, was largely unknown until Dawn spacecraft explored it in early 2015. However, certain surface features such as "Piazzi", named after the dwarf planets' discoverer, had been resolved.[a] Ceres's oblateness is consistent with a differentiated body, a rocky core overlain with an icy mantle.
This represented a choice between having a set of three distinct categories of body (planet, "dwarf planet" and SSSB) and the opening of an umbrella of 'planets' over the first two such categories. The Resolution proposed the latter option; it was defeated convincingly, with only 91 [46] members voting in its favour.
However, WD 1145+017 b is not massive enough to qualify as a sub-Earth classical planet and is instead defined as a minor, or dwarf, planet. [2] It is orbiting within a thick cloud of dust and gas as chunks of itself continually break off to then spiral in towards the star, and within around 5,000 years it will have more-or-less disintegrated. [3]
Also amphidrome and tidal node. A geographical location where there is little or no tide, i.e. where the tidal amplitude is zero or nearly zero because the height of sea level does not change appreciably over time (meaning there is no high tide or low tide), and around which a tidal crest circulates once per tidal period (approximately every 12 hours). Tidal amplitude increases, though not ...