Triton
Moon· orbits Neptune
Triton is Neptune's largest moon and the only large moon orbiting backwards (retrograde) — a captured Kuiper-belt world with a young nitrogen-ice surface and active nitrogen geysers, seen by Voyager 2 in 1989.
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Key facts
Mass
2.14 × 10²² kg
0.291 Moon masses
Radius
1,353 km
78% of our Moon's radius
Surface gravity
0.78 m/s²
8% of Earth's
Day length
5.9 days
Orbit around Neptune
5.88 Earth days
Science
Physical
- Mass
- 2.14 × 10²² kg · 0.291 Moon masses
- Radius
- 1,353 km · 78% of our Moon's radius
- Density
- 2,064 kg/m³ · 2.1× water
- Surface gravity
- 0.78 m/s² · 8% of Earth's
- Escape velocity
- 1.45 km/s · 13% of Earth's
Orbit around Neptune
- Distance from Neptune
- 2,704,826 km
- Orbital period
- 5.9 days
- Eccentricity
- 0
- Inclination
- 157.30 °
Rotation
- Rotation period
- 5.9 days
- Tidal locking
- Tidally locked to its parent
Atmosphere
- Composition
- Tenuous N₂ with traces of CH₄ and CO
- Surface pressure
- 1.4 Pa
Temperature
- Surface
- 38 K (-235 °C)
Composition
- Bulk composition
- A nitrogen-ice surface (with CO₂, CO and methane ices) over a water-ice crust and a large rocky core; one of the coldest measured surfaces in the Solar System.
Radiation & temperature
- Insolation
- 0.00112 S⊕ · 1/893 of the sunlight Earth receives
- Bond albedo
- 0.76 · reflects 76% of incoming sunlight
- Equilibrium temperature
- 36 K (-238 °C)
- Surface temperature
- 38 K (-235 °C)
Discovery & history
- Discovered
- October 10, 1846
- By
- William Lassell
- Method
- Visual discovery (telescopic)
- Name
- Triton, a sea-god son of Poseidon (Neptune) in Greek myth.
William Lassell discovered Triton just 17 days after Neptune itself was found in 1846. It orbits backwards — the only large moon to do so — marking it as a captured Kuiper Belt object. Voyager 2 found it geologically active, with nitrogen geysers erupting from one of the coldest surfaces ever measured.
Images
Images from open archives · credit shown per image