Ice giant

Neptune

Neptune is the wind-sculpted outer planet, with dynamic storms and Triton, a captured Kuiper Belt object.

Neptune: loading local 3D asset.

Physics Snapshot

Planet order
8 from the Sun
Planet class
Outer ice giant
Mean distance
30.069 AU
Revolution period
60,182 Earth days
Rotation period
16 h 6 m 36 s
Relative rotation speed
22.346 deg/s display
Mean temperature
-200 C mean cloud-top temperature
Atmosphere
Dynamic ice-giant atmosphere with methane clouds, dark vortices, and powerful winds.
Main gases
Mostly hydrogen and helium with methane and trace hydrocarbons.
Surface / cloud pressure
No solid surface; 1-bar atmospheric level is used as a reference.
Ocean status
No surface ocean. Interior likely contains high-pressure water-ammonia-methane fluids; Triton may host a subsurface ocean.
Perihelion / closest
29.81 AU (4.471 billion km)
Aphelion / farthest
30.33 AU (4.559 billion km)
Orbit ellipse
0.0090
Mean/reference radius
24,622 km
Gravity definition
11.15 m/s²
Escape velocity
23.5 km/s
Day length
16.1 hours
Known moons
16 confirmed
Mission record
Voyager 2 remains the only spacecraft encounter; telescopes track long-term weather and ring arcs.

What Scientists Watch

Classification: Outer ice giant. Mercury through Mars are inner rocky worlds; Jupiter through Neptune are outer giants.

  • Supersonic winds and dark vortices show active weather far from the Sun.
  • Triton's retrograde orbit suggests capture and possible internal ocean activity.
  • Neptune anchors studies of exoplanet ice giants, a common planetary class.

Exploration note: Voyager 2 remains the only spacecraft encounter; telescopes track long-term weather and ring arcs.

Atmosphere and oceans

Gases, temperature, and liquids

Atmosphere
Dynamic ice-giant atmosphere with methane clouds, dark vortices, and powerful winds.
Main gases
Mostly hydrogen and helium with methane and trace hydrocarbons.
Pressure
No solid surface; 1-bar atmospheric level is used as a reference.
Surface / cloud temperature
About -200 C near the cloud-level reference region; deeper layers are much warmer.
Oceans and liquids
No surface ocean. Interior likely contains high-pressure water-ammonia-methane fluids; Triton may host a subsurface ocean.
Stable surface liquids
No hard surface; volatile-rich interior exists at extreme pressure.

Interpretation note

How to read these values

Rocky worlds list surface conditions directly. Jupiter, Saturn, Uranus, and Neptune do not have hard surfaces, so temperature and pressure are referenced to atmospheric levels such as the 1-bar cloud region.

Ocean status separates the planet itself from its moons. Several outer-planet moons are major ocean-world targets even when the parent planet has no surface ocean.

3D asset view

Rotatable planet model

Neptune: loading local 3D asset.

This viewer loads the local asset-backed model for Neptune and applies the sidereal axis tilt and relative rotation direction for study. Drag to rotate, wheel to zoom, and open full screen for close inspection.

Elevation and relief

Topography map notes

  • As with Uranus, Neptune has no solid visible relief map, so the elevation-style study shifts to cloud morphology, storms, and zonal wind structure.
  • The Great Dark Spot class of vortices, bright companion clouds, and high-latitude dynamics define the atmospheric landscape.
  • Triton and the ring arcs are important system context even though they are not part of the planet's cloud deck itself.

Interior and field

Core, mantle, and magnetism

Upper atmosphere
Hydrogen-helium envelope with methane clouds and strong weather activity
Icy mantle
High-pressure water-ammonia-methane fluid interior
Core
Rocky heavy-element core under deep-pressure conditions

Orbital characteristics

Detailed orbit solution

Epoch
J2000
Perihelion
29.81 AU (4.471 billion km)
Aphelion
30.33 AU (4.559 billion km)
Semi-major axis
30.1104 AU (4.498 billion km)
Eccentricity
0.0090
Sidereal period
60,182 Earth days
Synodic period
367.49 Earth days
Average orbital speed
5.43 km/s
Inclination
1.770 deg to the ecliptic
Longitude of ascending node
131.784 deg
Argument of perihelion
273.187 deg

Physical characteristics

Bulk properties and rotation

Mean radius
24,622 km
Flattening
0.01708
Surface area
7.6183 billion km²
Volume
62.54 trillion km³
Mass
1.02413 × 10²⁶ kg
Mean density
1.638 g/cm³
Reference gravity
11.15 m/s²
Escape velocity
23.5 km/s
Sidereal rotation
16 h 6 m 36 s
Equatorial rotation speed
About 2.68 km/s
Axial tilt
28.32 deg
Geometric albedo
0.442

Atmosphere profile

Pressure, composition, and temperature

Pressure reference
1-bar cloud level
Composition
Mostly hydrogen and helium with methane and trace hydrocarbons
Cloud-top temperature
About -200 C
Dynamics
Fast winds, dark vortices, and bright methane-ice clouds

Field review

Magnetic field, core behavior, and crater context

  • Neptune's magnetic field is also strongly tilted and offset, implying a non-central dynamo region similar in spirit to Uranus.
  • Its magnetosphere is highly asymmetric and rotates through the solar wind with a geometry that is much less Earth-like than a simple dipole.
No stable cratered cloud-top surface is visibleGreat Dark Spot class vorticesBright methane-ice cloud bandsRing arcs

Moon catalog

Moons Available

Confirmed count: 16 confirmed

Naiad, Thalassa, Despina, Galatea, Larissa, Hippocamp, Proteus, Triton, Nereid, Halimede, Sao, Laomedeia, Psamathe, Neso, S/2002 N 5, and S/2021 N 1.

Data note: rotation values are sidereal periods. For solar orbits this guide uses perihelion and aphelion; those are the Sun-orbit equivalents of closest and farthest orbital distance. Gravity is surface or equatorial gravity for rocky planets and a reference-level value for giant planets, so rounded fact sheets may differ slightly. Moon counts can change when new satellites are confirmed.

Data basis

How these values are normalized

Orbital elements are presented in a J2000-style reference format. Rotation values use sidereal periods unless a solar day is explicitly named. For giant planets, pressure, temperature, and gravity are reference-level values because there is no solid surface to stand on.

Audit note

How to read discrepancies

Compact summary boxes, environment notes, and detailed fact tables are now aligned to the same field guide data blocks. This consistency pass was updated on May 5, 2026. Small differences can still appear when a quantity is rounded for readability, when a rocky-planet surface value is contrasted with a giant-planet reference level, or when moon counts change after new confirmations.

Mathematical model

Planet rotation and scale model

Planet meshes are procedural study models: radius, axial tilt, and rotation come from catalog fields, while surface textures are visual aids. The mathematical model does not infer planet shape from a picture.

Rotation phase

\[\theta(t)=\theta_0+\frac{2\pi t}{P_{\mathrm{rot}}}\]

The displayed spin angle advances from the body's rotation period P_rot. Retrograde rotation is represented by the sign of P_rot.

Axial tilt

\[\mathbf{r}_{\mathrm{tilted}}=R_z(\varepsilon)\,\mathbf{r}_{\mathrm{body}}\]

The spin axis is tilted by an explicit obliquity epsilon. The proof is a rigid-body rotation matrix, not an artist-drawn axis.

Scale contract

\[R_{\mathrm{scene}}=k\,R_{\mathrm{catalog}}\]

Scene radius is a scalar multiple of catalog radius unless the user chooses a readability mode. The page states when visual radius is bounded so the model is not mistaken for exact visual scale.

Verification standard: the rendered object must be reproducible from stated equations, catalog parameters, or explicit geometric transforms. Visual reference images may inform presentation only; they are not the source of orbital positions, field vectors, accretion-disk gradients, timing, or engineering layout.

Limitations: browser scenes may use bounded scale, compressed distances, simplified two-body dynamics, schematic transfer curves, or educational approximations where full numerical ephemerides, CFD, finite-element models, or general-relativistic ray tracing are outside the page scope. Those simplifications are part of the model contract, not hidden image-based construction.

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