Planet: Difference between revisions

[[File:Planet_collage_to_scale.jpg|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 (planet)|Mercury]] (inner planets)]]

The word ''planet'' comes from the Greek {{lang|grc|[[wikt:πλανήτης#Ancient Greek|πλανήται]]}} ({{Transliteration|grc|planḗtai}}) {{gloss|wanderers}}. In [[Classical antiquity|antiquity]], this word referred to the [[Sun]], [[Moon]], and five points of light visible to the naked eye that moved across the background of the stars—namely, Mercury, Venus, Mars, Jupiter, and Saturn. Planets have historically had religious associations: [[History of astronomy#Early History|multiple cultures]] identified celestial bodies with gods, and these connections with mythology and [[folklore]] persist in the schemes for naming newly discovered Solar System bodies. Earth itself was recognized as a planet when [[heliocentrism]] supplanted [[Geocentric model|geocentrism]] during the 16th and 17th centuries.

[[File:Solar System true color (captions).jpg|center|thumb|600x600px|The Sun's, planets', dwarf planets' and moons' size to scale, labelled. Distance of objects is not to scale. The asteroid belt lies between the orbits of Mars and Jupiter, the Kuiper belt lies beyond Neptune's orbit.]]

Dwarf planets are gravitationally rounded, but have not cleared their orbits of other [[Small Solar System body|bodies]]. In increasing order of average distance from the Sun, the ones generally agreed among astronomers are {{dp|Ceres}}, {{dp|Orcus}}, {{dp|Pluto}}, {{dp|Haumea}}, {{dp|Quaoar}}, {{dp|Makemake}}, {{dp|Gonggong}}, {{dp|Eris}}, and {{dp|Sedna}}.<ref name=Grundy2019/><ref name=JWST/> Ceres is the largest object in the [[asteroid belt]], located between the orbits of Mars and Jupiter. The other eight all orbit beyond Neptune. Orcus, Pluto, Haumea, Quaoar, and Makemake orbit in the [[Kuiper belt]], which is a second belt of small Solar System bodies beyond the orbit of Neptune. Gonggong and Eris orbit in the [[scattered disc]], which is somewhat further out and, unlike the Kuiper belt, is unstable towards interactions with Neptune. Sedna is the largest known [[detached object]], a population that never comes close enough to the Sun to interact with any of the classical planets; the origins of their orbits are still being debated. All nine are similar to terrestrial planets in having a solid surface, but they are made of ice and rock rather than rock and metal. Moreover, all of them are smaller than Mercury, with Pluto being the largest known dwarf planet and Eris being the most massive.<ref name="Brown Schaller 2007">{{cite journal| doi = 10.1126/science.1139415| last1 = Brown| first1 = Michael E.| author-link = Michael E. Brown| last2 = Schaller| first2 = Emily L.| s2cid = 21468196| date = 15 June 2007| title = The Mass of Dwarf Planet Eris| journal = Science| volume = 316| issue = 5831| page = 1585| pmid = 17569855| bibcode = 2007Sci...316.1585B| url = http://hubblesite.org/pubinfo/pdf/2007/24/pdf.pdf| access-date = 27 September 2015| archive-url = https://web.archive.org/web/20160304053122/http://hubblesite.org/pubinfo/pdf/2007/24/pdf.pdf| archive-date = 4 March 2016}}</ref><ref>{{cite web |url=https://www.nasa.gov/feature/how-big-is-pluto-new-horizons-settles-decades-long-debate |title=How Big Is Pluto? New Horizons Settles Decades-Long Debate |website=NASA |date=7 August 2017 |access-date=5 May 2022 |archive-date=9 November 2019 |archive-url=https://web.archive.org/web/20191109182908/https://www.nasa.gov/feature/how-big-is-pluto-new-horizons-settles-decades-long-debate/ |url-status=dead }}</ref>