What Is the Definition of a Dwarf Planet

There is no single «right» definition of dwarf planets, no matter what HeadAroundU says. There are several competing definitions, all of which are based on science. Planets and dwarf planets differ at the last point. A planet`s gravity would attract or repel small bodies obstructing its orbit, but the dwarf planet`s gravity is not enough to achieve this. Currently, five dwarf planets, namely Ceres, Pluto, Eris, Haumea and Makemake, have been discovered. Scientists suspect there may be more than a hundred dwarf planets waiting to be discovered. Dwarf planets are celestial bodies too small to be considered a planet, but too large to fall into smaller categories. The International Astronomical Unit defines a planet as something that meets the following criteria: Dawn had previously orbited the asteroid Vesta. Saturn`s moon Phoebe was imaged by Cassini and before that by Voyager 2, which also hit Neptune`s moon Triton.

All three bodies indicate that they were once dwarf planets, and their study helps clarify the evolution of dwarf planets. The number of dwarf planets among the known bodies of the solar system varies from 5 to more than 120 (Runyon et al). [2] Apart from Sedna, the largest of these candidates have either been visited by space probes (Pluto and Ceres), or have at least one known moon (Pluto, Eris, Haumea, Makemake, Gonggong, Quaoar, Orcus, Salacia), which makes it possible to determine their masses and therefore an estimate of their density. Mass and density, in turn, can be inserted into geophysical models to determine the nature of these worlds. There is no clear definition of what constitutes a dwarf planet, and whether an object should be classified as such is up to individual astronomers. Therefore, the number of dwarf planets in the solar system is unknown. Dynamic scientists generally prefer to use gravitational dominance as a threshold for the planetary tree, because from their point of view, smaller bodies are better grouped with their neighbors, for example Ceres as a simple large asteroid and Pluto as a large Kuiper belt object. [45] [46] However, geoscientists generally prefer roundness as a threshold because the internal geology of a body like Ceres is closer to a classical planet like Mars from their point of view than to a small asteroid that has no internally controlled geology. This necessitated the creation of the category of dwarf planets to describe this intermediate class.

[44] Unfortunately, most of the sites you recommend only promote the IAU definition. For the sake of fairness, you really need to offer readers both sides of this issue. Pluto will never again be considered a large planet. We either have 8 planets or we have 90+ and we climb. A quick look at Mike Brown`s website shows this. And that doesn`t even include the solar system`s 19 spherical moons. (Salacia was later found to have a slightly higher density, comparable in uncertainties to that of Orcus, although it still has a very dark surface. Despite this determination, Grundy et al. referred to it as a «dwarf planet» while calling Orcus a dwarf planet. [70] Subsequent studies on Varda suggest that its density may also be high.) [71] On June 11, 2008, the IAU Executive Committee announced a new term, plutoid, and a definition: All trans-Neptunian dwarf planets are plutoids.

[36] The authority of this first announcement has not been generally recognized: Le 14. In July 2015, NASA`s New Horizons spacecraft flew by Pluto, providing numerous imagery, spectroscopy, and in situ datasets that radically changed our knowledge of Pluto and its five-moon system. The images showed that Pluto is larger than Eris and is the largest body in the Kuiper belt. The images also showed a remarkable landscape with a variety of landforms, including vast plains, mountain ranges several kilometers high, and evidence of volcanoes. Pluto`s surface is unusual for its variety of surface compositions and colors. Some areas are as light as snow and others as dark as charcoal. Color imaging and composition spectroscopy revealed a very complex distribution of surface ice, including nitrogen, carbon monoxide, water and methane, as well as their chemical by-products produced by radiolysis. Some surfaces on Pluto have also been found to be completely free of visible craters, suggesting that they were altered or created in the recent past. Other surfaces are heavily dotted with craters and appear extremely old.

Pluto is enveloped by a cold atmosphere dominated by nitrogen containing a thin layer of very extensive haze about 150 km thick. Charon, Pluto`s great moon, shows impressive tectonics and evidence of heterogeneous crustal composition, but no evidence of an atmosphere; Its mast shows a mysterious dark terrain. No new satellites have been discovered, nor have the rings. The small Hydra and Nix satellites have brighter surfaces than expected. These findings raise fundamental questions about how a small, cold planet can remain active during the age of the solar system. They show that dwarf planets can be just as interesting scientifically as planets. Equally important, the three great Kuiper belts visited by spacecraft so far – Pluto, Charon and Triton – are more different than similar, testifying to the potential diversity that awaits the exploration of their empire. Understanding what a dwarf planet is according to the IAU is simple enough, but placing the solar system in a three-level classification system will prove increasingly difficult as our understanding of the universe grows and we are able to see farther and farther into space. Keep in mind that Mercury is twice as massive as Titan. Mass is what makes a planet dominate its region. As of 2011, Stern still referred to Pluto as a planet and accepted other dwarf planets such as Ceres and Eris as well as the larger moons as additional planets. However, other astronomers have countered this view by saying that far from having left their orbits, large planets completely control the orbits of other bodies in their orbital zone.

The IAU has been responsible for naming and naming planetary bodies and their satellites since the early 1900s. Professor Ron Ekers, former IAU President, explains: At the time Makemake and Haumea were named, it was thought that trans-Neptunian objects (TNO) with icy cores would require a diameter of only about 400 km (250 miles), or 3% of the size of the Earth – the size of the moons Mimas, the smallest round moon, and Proteus, the largest, which it is not – to relax in gravitational balance. [63] The researchers thought the number of these bodies in the Kuiper belt could be about 200, with thousands more than that. [63] [64] [65] This was one of the reasons (limiting the list of «planets» to a reasonable number) why Pluto was reclassified in the first place. Since then, however, research has cast doubt on the idea that such small bodies could have achieved or maintained balance under conditions typical of the Kuiper belt and beyond. On the other hand, there is something that delineates a moon from a planet – moons cannot have lasting moons. Apparently, tidal interactions will crash or eject something into orbit around a moon.