Where is it now
- Distance from Sun
- 29.889 AU
- True anomaly
- 313.97°
- Distance from Earth
- 28.898 AU
- As of
- 2 October 2026
Two-body Kepler propagation — accurate to ~0.1% for major planets over decades, less so for highly-perturbed bodies. Use JPL Horizons for high precision.
In the sky
- Right ascension
- 00h 08m 51s
- Declination
- -00° 34′ 37″
- Constellation
- Pisces
- Distance from Earth
- 28.9 AU
- Elongation from the Sun
- 171.48° — near opposition — up most of the night
Visible from both hemispheres.
From your location
See how high it is right now, whether it's up after dark, and when it rises and sets where you are.
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Two-body approximation, good to about a degree for the planets — enough to find the constellation and know whether it is up.
Orbital elements
- Semi-major axis
- 30.07 AU
- Eccentricity
- 0.0086
- Inclination
- 1.77°
- Orbital period
- 164.8 years
- Perihelion
- 29.811 AU
- Aphelion
- 30.327 AU
- Longitude of ascending node
- 131.78°
- Argument of periapsis
- 276.34°
- Epoch · J2000
- J2000
Physical properties
- Mean radius
- 24,622 km
- Equatorial radius
- 24,764 km
- Polar radius
- 24,341 km
- Mass
- 1.024 × 10²⁶ kg
- Density
- 1.638 g/cm³
- Rotation period
- 16.11 hours
- Axial tilt
- 28.32°
- Surface gravity
- 11.27 m/s²
- Escape velocity
- 23.5 km/s
- GM
- 6,835,100 km³/s²
- Ellipticity
- 0.01708
- Length of day
- 16.11 hours
- Synodic period
- 367.5 days
- Mean orbital speed
- 5.45 km/s
- Black-body temperature
- 46.6 K
- Solar irradiance
- 1.5 W/m²
Visual & observation
- Geometric albedo
- 0.442
- Bond albedo
- 0.29
- V(1,0) magnitude
- -6.94
- Representative colour
- #3F5BAA
Discovery & classification
- Discovered by
- Urbain Le Verrier, Johann Galle, Heinrich d'Arrest
- Discovery date
- 23 September 1846
Atmosphere
- Surface pressure · >>1000 bars
- 1,000 bar
- Temperature · 72 K (-201 C)
- 72 K
- Density
- 0.45 kg/m³
- Mean molecular weight
- 2.53
- Winds
- 0-580 m/s
Composition by volume
- Molecular hydrogen (H2) 80 %
- Helium (He) 19 %
- Hydrogen Deuteride (HD) 192 ppm
- Ethane (C2H6) 2 ppm
Source: NASA Planetary Fact Sheet.
Ring system
| Ring | Inner radius | Outer radius | Width |
|---|---|---|---|
| Galle Ring | 40,900 km | 42,900 km | 2,000 km |
| Le Verrier Ring | 53,200 km | 53,200 km | 0.00 km |
| Lassell Ring | 53,200 km | 57,200 km | 4,000 km |
| Arago Ring | 57,200 km | 57,200 km | 0.00 km |
| Adams Ring | 62,930 km | 62,930 km | 0.00 km |
16 moons
| Naiad | 29 km | 1.278 × 10¹⁷ kg | 1.25 g/cm³ | 0.0003 AU | 7.1 hours |
| Thalassa | 40 km | 3.534 × 10¹⁷ kg | 1.32 g/cm³ | 0.0003 AU | 7.5 hours |
| Despina | 74 km | 1.749 × 10¹⁸ kg | 1.03 g/cm³ | 0.0004 AU | 8 hours |
| Galatea | 79 km | 2.845 × 10¹⁸ kg | 1.38 g/cm³ | 0.0004 AU | 10.3 hours |
| Larissa | 96 km | 3.818 × 10¹⁸ kg | 1.03 g/cm³ | 0.0005 AU | 13.3 hours |
| Hippocamp | — | — | — | 0.0007 AU | 22.8 hours |
| Proteus | 208 km | 3.871 × 10¹⁹ kg | 1.03 g/cm³ | 0.0008 AU | 26.9 hours |
| Triton | 1,353 km | 2.139 × 10²² kg | 2.06 g/cm³ | 0.0024 AU | 5.9 days |
| Nereid | 170 km | 3.1 × 10¹⁹ kg | — | 0.0369 AU | 360.1 days |
| Halimede | — | — | — | 0.1109 AU | 5.14 years |
| Sao | — | — | — | 0.1487 AU | 7.99 years |
| S/2002 N 5 | — | — | — | 0.1565 AU | 8.63 years |
| Laomedeia | — | — | — | 0.1571 AU | 8.67 years |
| Psamathe | — | — | — | 0.3185 AU | 25.05 years |
| Neso | — | — | — | 0.3335 AU | 26.84 years |
| S/2021 N 1 | — | — | — | 0.3389 AU | 27.5 years |
Sources
- orbital elements: NASA Planetary Fact Sheet / JPL keplerian elements
- physical properties: NASA Planetary Fact Sheet
- visual properties: NASA Planetary Fact Sheet
- physical properties: NASA Planetary Fact Sheet
- visual properties: NASA Planetary Fact Sheet
- atmospheres: NASA Planetary Fact Sheet