Neptune

Also known as ♆, Sol VIII, Sol 8

Neptune is the eighth and farthest known planet orbiting the Sun. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times the mass of Earth. Compared to Uranus, its neighbouring ice giant, Neptune is slightly smaller, but more massive and denser. Being composed primarily of gases and liquids, it has no well-defined solid surface. Neptune orbits the Sun once every 164.8 years at an orbital distance of . It is named after the Roman god of the sea and has the astronomical symbol representing Neptune's t

AI overview

Neptune is the eighth and farthest planet from the Sun, composed primarily of gases and liquids with no solid surface, making it an ice giant about 17 times Earth's mass. It matters as a key member of our Solar System that helps us understand planetary diversity, and studying it reveals important information about how planets form and behave in the outer reaches of our cosmic neighborhood.

AI-generated from the Wikipedia summary — may contain errors.

Key facts

Planet.name: Neptune
Planet.symbol: 24px|♆|class=skin-invert, 24px|⯉|class=skin-invert
Planet.image: Neptune Voyager2 color calibrated.png
Planet.caption: Neptune in true colour, taken by Voyager 2 on August 25, 1989; at centre is the Great Dark Spot
Planet.background: LightBlue
Planet.discovered: 23 September 1846
Planet.pronounced: ,
Planet.adjectives: Neptunian (), Poseidean
Planet.named_after: Latin , via French
Planet.epoch: J2000
Planet.apsis: helion
Planet.time_periastron: 2042-Sep-04
Planet.synodic_period: 367.49 days
Planet.inclination: to ecliptic6.43° to Sun's equator0.74° to invariable plane
Planet.satellites: 16
Planet.equatorial_radius: 3.883 Earths
Planet.polar_radius: 3.829 Earths
Planet.surface_area: 14.94 Earths

via Wikipedia infobox

Research

3,015 papers

Clarifications: NEPTUNE Study.Indian pediatrics · 2026Jain A, Majumder SDOI: 10.1007/s13312-026-00356-x
Neptune, the Next Pluto?-Durvalumab and Tremelimumab Face Challenges in Entering the NSCLC Space.Journal of thoracic oncology : official publication of the International Association for the Study of Lung Cancer · 2023Ahn JY, Nagasaka MDOI: 10.1016/j.jtho.2022.11.004
A super-massive Neptune-sized planet.Nature · 2023Naponiello L, Mancini L, Sozzetti A et al.DOI: 10.1038/s41586-023-06499-2
Neptune: an environment for the delivery of genomic medicine.Genetics in medicine : official journal of the American College of Medical Genetics · 2021Eric V, Yi V, Murdock D et al.DOI: 10.1038/s41436-021-01230-w
The Nature and Origins of Sub-Neptune Size Planets.ReviewJournal of geophysical research. Planets · 2021Bean JL, Raymond SN, Owen JEDOI: 10.1029/2020JE006639
Pediatric contributions and lessons learned from the NEPTUNE cohort study.ReviewPediatric nephrology (Berlin, Germany) · 2024Modi ZJ, Zhai Y, Yee J et al.DOI: 10.1007/s00467-023-06256-7
Looking at Neptune with a binocular.Hepatology (Baltimore, Md.) · 2025Vizzutti F, Thabut DDOI: 10.1097/HEP.0000000000001106
NEPTUNE: Phase 3 Study of First-Line Durvalumab Plus Tremelimumab in Patients With Metastatic NSCLC.Journal of thoracic oncology : official publication of the International Association for the Study of Lung Cancer · 2023de Castro G Jr, Rizvi NA, Schmid P et al.DOI: 10.1016/j.jtho.2022.09.223

via PubMed

Wikidata facts

Demonym: Neptunano
Area: 7618300000
Distance from Earth: 4600000000
Diameter: 49528
Radius: 24341
Mass: 102430
Orbital period: 60193.2
Image: Neptune Voyager2 color calibrated.png

Show 23 more facts

Commons category: Neptune (planet)
orbital eccentricity: 0.009456
time of discovery or invention: 1846-09-23
Commons gallery: Neptune (planet)
semi-major axis of an orbit: 30.06992276
orbital inclination: 0.72
argument of periapsis: 44.96476227
longitude of ascending node: 131.78422574
Unicode character: ♆
synodic period: 367.49
flattening: 0.0171
magnetic moment: 2200000000000000016777216
apoapsis: 4537039826
periapsis: 4459753056
surface gravity: 11
density: 1.638
mean anomaly: 256.228
volume as quantity: 62540000000000
temperature: 72
apparent magnitude: 8
angular diameter: 2.4
Stack Exchange tag: astronomy.stackexchange.com/tags/neptune
rotation period: 16

Sources (15)

via Wikidata · CC0

~45 min read

Article

28 sections

Contents

History
Discovery
Naming
Status
Formation
Bulk properties
Internal structure
Internal heating
Rotation
Magnetosphere
Surficial characteristics
Colour
Atmosphere
Climate
Storms
Orbital motion and observation
Observation
Gravitational domain and influence
Planetary rings
Moons
Orbital resonances
Exploration
See also
Notes
References
Bibliography
Further reading
External links

Neptune is not visible to the unaided eye and is the only planet in the Solar System that was not initially observed by direct empirical observation. Rather, unexpected changes in the orbit of Uranus led Alexis Bouvard to hypothesise that its orbit was subject to gravitational perturbation by an unknown planet. After Bouvard's death, the position of Neptune was mathematically predicted from his observations, independently, by John Couch Adams and Urbain Le Verrier. Neptune was subsequently directly observed with a telescope on 23 September 1846 by Johann Gottfried Galle within a degree of the position predicted by Le Verrier. Its largest moon, Triton, was discovered shortly thereafter, though none of the planet's remaining moons were located telescopically until the 20th century.