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Glossary term: Neptune

Description: Neptune is the eighth, and farthest, major planet from the Sun. Like its neighbor Uranus, Neptune is an ice giant. Neptune's radius is a little less than four times Earth's radius and it has no firm surface. Neptune has a solid rock core surrounded by a layer of high-pressure water, methane, and ammonia. In the early outer Solar System these chemicals were frozen and accreted onto the young Neptune, hence the name "ice giant". Neptune's outer atmosphere is a thick, puffy layer of hydrogen and helium. Neptune has at least 14 moons and a faint ring system. As the outermost major planet, Neptune's gravity plays a pivotal role in shaping the orbits of smaller bodies in the Kuiper Belt.

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The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".

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Neptune is spherical and blue with thin bands of white cloud and a slightly darker spot just below its equator

Neptune

Caption: Voyager 2 Narrow Angle Camera image of Neptune taken in August 1989. The Great Dark Spot, flanked by cirrus clouds, is at center. A smaller dark storm, Dark Spot Jr., is rotating into view at bottom left. Additionally, a patch of white cirrus clouds to its north, named "Scooter" for its rapid motion relative to other features, is visible.
Credit: NASA / JPL / Voyager-ISS / Justin Cowart credit link
License: PD Public Domain icons