page_title: Neptune
section_title: Formation and migration
hierarchical_section_title: Neptune / Formation and migration
caption_attribution_description: English: Simulation showing the outer planets and the Kuiper belt: a) Before Jupiter–Saturn 2:1 resonance. b) Scattering of Kuiper belt objects into the Solar System after the orbital shift of Neptune. c) After ejection of Kuiper belt bodies by Jupiter. Planets shown: Jupiter (green circle), Saturn (orange circle), Uranus (light blue circle), and Neptune (dark blue circle). Simulation created using data from the Nice Model.&#91;1&#93; Français&#160;: Simulation montrant les planètes externes et la ceinture de Kuiper&#160;: a) Avant la résonance 2:1 de Jupiter et Saturne. b) Dispersion des objets de la ceinture de Kuiper dans le système solaire après la migration de Neptune. c) Après l'éjection d'objets de la ceinture de Kuiper par Jupiter. L'orbite de Jupiter est représentée en vert, Saturne en orange, Uranus en bleu clair et Neptune en bleu foncé. Simulation créée sur la base de données du Nice Model&#91;1&#93; Deutsch: Eine Simulation, die die äußeren Planeten und den Kuipergürtel zeigt: a) Vor der Jupiter/Saturn 2:1 Resonanz. b) Zerstreuung der Objekte des Kuipergürtels in das Sonnensystem, nachdem sich die Umlaufbahn Neptuns verschoben hatte. c) Nach dem Ausstoß von Objekten des Kuipergürtels durch Jupiter. Gezeigte Planeten: Jupiter (grüner Kreis), Saturn (oranger Kreis), Uranus (hellblauer Kreis) und Neptun (dunkelblauer Kreis). Die Simulation wurde mit Hilfe von Daten des Nice Models erstellt.&#91;1&#93; Čeština: Simulace vlivu vnějších planet na vývoj Kuiperova pásu: a) Kuiperův pás před tím, než se planety Jupiter a Saturn dostaly do vzájemné dráhové rezonance 2:1. b) Rozptýlení těles Kuiperova pásu poté, co začal měnit svou oběžnou dráhu Neptun. c) Rozptýlená tělesa se dostávala do vlivu Jupiteru, který je vymrštil pryč. Zobrazené planety: Jupiter (zelený kruh), Saturn (oranžový kruh), Uran (bledě modrý kruh) a Neptun (tmavě modrý kruh). Simulace byla vytvořena za použití údajů z tzv. Modelu z Nice.&#91;1&#93;
context_page_description: Neptune is the eighth and farthest-known planet from the Sun. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times the mass of Earth, slightly more massive than its near-twin Uranus. Neptune is denser and physically smaller than Uranus because its greater mass causes more gravitational compression of its atmosphere. The planet orbits the Sun once every 164.8 years at an average distance of 30.1 AU. It is named after the Roman god of the sea and has the astronomical symbol ♆, a stylised version of the god Neptune's trident.
  Neptune is not visible to the unaided eye and is the only planet in the Solar System found by mathematical prediction rather than by empirical observation. Unexpected changes in the orbit of Uranus led Alexis Bouvard to deduce that its orbit was subject to gravitational perturbation by an unknown planet. After Bouvard's death, the position of Neptune was predicted from his observations, independently, by John Couch Adams and Urbain Le Verrier.
context_section_description: The formation of the ice giants, Neptune and Uranus, has proven difficult to model precisely. Current models suggest that the matter density in the outer regions of the Solar System was too low to account for the formation of such large bodies from the traditionally accepted method of core accretion, and various hypotheses have been advanced to explain their formation. One is that the ice giants were not formed by core accretion but from instabilities within the original protoplanetary disc and later had their atmospheres blasted away by radiation from a nearby massive OB star.
  An alternative concept is that they formed closer to the Sun, where the matter density was higher, and then subsequently migrated to their current orbits after the removal of the gaseous protoplanetary disc. This hypothesis of migration after formation is favoured, due to its ability to better explain the occupancy of the populations of small objects observed in the trans-Neptunian region. The current most widely accepted explanation of the details of this hypothesis is known as the Nice model, which explores the effect of a migrating Neptune and the other giant planets on the structure of the Kuiper belt.
caption: A simulation showing the outer planets and Kuiper belt: a) before Jupiter and Saturn reached a 2:1 resonance; b) after inward scattering of Kuiper belt objects following the orbital shift of Neptune; c) after ejection of scattered Kuiper belt bodies by Jupiter
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