Neptune

The mathematician's planet

Vital statistics

• Mean radius: 24,622 kilometres
• Mass: 1.02 × 10²⁶ kilograms
• Surface gravity: 11.15 metres per second squared
• Sidereal rotation: 16.1 hrs
• Orbital period: 164.8 yrs
• Mean temperature: -200 °C
• Known moons: 16
• Axial tilt: 28.32 degrees

Field notes

• Neptune was discovered with mathematics before telescopes: predicted from wobbles in Uranus's orbit, it was found within 1° of the predicted spot, on the first night of searching.
• Its winds reach 2,100 km/h — the fastest in the solar system, faster than sound on Earth — powered by sunlight 900× weaker than ours. How? Nobody is sure.
• Deep inside, it probably rains diamonds: carbon squeezed into glittering hail that sinks toward the core.
• It has completed exactly one orbit since humans discovered it in 1846.

Data: NASA Planetary Fact Sheets. Explore the full interactive 3D map at the home page — every orbit is computed from real Keplerian elements.