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Neptune (mag. 8.0) was in conjunction on February 2nd, 2004, only 19 days before Uranus, and will be in the morning sky until its opposition on August 5th, 2004. The next conjunction will be on February 3rd, 2005. |
| Property | Unit | Value |
|---|---|---|
| Mass | kg | 1.02 x 10^26 |
| Diameter | km | 49528 |
| Mean density | kg/m^3 | 1640 |
| Escape velocity | m/sec | 23300 |
| Average distance from Sun | AU | 30.06 |
| Rotation period (length of day) | Earth hours | 19.1 |
| Revolution period (length of year) | Earth years | 164.8 |
| Obliquity (tilt of axis) | degrees | 29.6 |
| Orbit inclination | degrees | 1.77 |
| Orbit eccentricity | deviation from circular | 0.009 |
| Mean temperature | ēK (ēC) | 48 (-225) |
| Visual geometric albedo | ratio (0 to 1) | 0.51 |
| Atmospheric components (at depth) | hydrogen helium methane |
74% 25% 1% |
| Rings are narrow, and contain concentrations of particles called ring arcs. |