| Mean distance from Sun: | 30.06 Astronomical Units 4,497,000,000 km |
|---|---|
| Diameter: | 49,500 km |
| Mass: | 17.23 Earths |
| Density: | 1.7 grams per cubic centimeter |
| Surface temperature: | Less than -250 F |
| Orbital period: | 164.79 years |
| Rotational period: | Approximately 17 hours, 50 minutes |
Similar in size and composition to Uranus, the eighth planet is so far from Earth that ground-based observations reveal little detail. Voyager 2 data confirm the presence of a tenuous ring system. Neptune's largest moon, Triton, may be glimpsed in telescopes of apertures of 30 cm.