Period of rotation (equatorial): *16 hr. 3 min. (19.2 hrs)
Mean orbital velocity per second: 3.4 miles (5.4 km)
Inclination of axis: 29.6░
Orbital eccentricity: 0.009
Orbital inclination: 1.77░
Diameter at equator: 30,780 miles
49,528 km
Earth????
Oblateness: 0.017
Escape velocity per second: 14.5 miles (23.9 km)
Mean surface temperature: -364 F / -220 C / 53 K (at cloud tops)
Mass: 1.02 x 10^26
(Earth = 1): 17
Volume (Earth =1): 57
Density (water = 1): 1.64
Surface gravity: 11.0 m/s^2
(Earth = 1): 1.12
Maximum apparent diameter as seen from Earth (seconds of arc): 2".2
Mean diameter of Sun as seen from the planet: 1' 04"
Albedo: 0.4
Number of known satellites: 8
Satellite statistics
N6
Mean distance from center of planet: 29,960 mi. (48,200 km)
Orbital period: 0.30 days
Orbital eccentricity: very low
Orbital inclination to planet's equator: 4.5░
Diameter: 31 mi. (50 km)
Escape velocity: ù
Magnitude: ù
Maximum apparent diameter as seen from the planet: ù
N5
Mean distance from center of planet: 31,100 mi. (50,000 km)
Orbital period: 0.31 days
Orbital eccentricity: very low
Orbital inclination to planet's equator: very low
Diameter: 56 mi. (90 km)
Escape velocity: ù
Magnitude: ù
Maximum apparent diameter as seen from the planet: ù
N3
Mean distance from center of planet: 32,600 mi. (52,500 km)
Orbital period: 0.33 days
Orbital eccentricity: very low
Orbital inclination to planet's equator: very low
Diameter: 87 mi. (140 km)
Escape velocity: ù
Magnitude: ù
Maximum apparent diameter as seen from the planet: ù
N4
Mean distance from center of planet: 38,500 mi. (62,000 km)
Orbital period: 0.40 days
Orbital eccentricity: very low
Orbital inclination to planet's equator: very low
Diameter: 100 mi. (160 km)
Escape velocity: ù
Magnitude: ù
Maximum apparent diameter as seen from the planet: ù
N2
Mean distance from center of planet: 45,700 mi. (73,600 km)
Orbital period: 0.56 days
Orbital eccentricity: very low
Orbital inclination to planet's equator: very low
Diameter: 124 mi. (200 km)
Escape velocity: ù
Magnitude: ù
Maximum apparent diameter as seen from the planet:ù
N1
Mean distance from center of planet: 73,089 mi. (117,600 km)
Orbital period: 1.12 days
Orbital eccentricity: very low
Orbital inclination to planet's equator: very low
Diameter: 260 mi. (420 km)
Escape velocity: ù
Magnitude: ù
Maximum apparent diameter as seen from the planet: ù
Triton
Mean distance from center of planet: 220,000 mi. (355,300 km)
Orbital period: 5.877 days
Orbital eccentricity: 0
Orbital inclination to planet's equator: 159.9░
Diameter: 1,690 mi. (2,720 km)
Escape velocity: ù
Magnitude: 13.6
Maximum apparent diameter as seen from the planet: 1░01"
Nereid
Mean distance from center of planet: 3,500,000 mi. (5,510,000 km)
Orbital period: 359.881 days
Orbital eccentricity: 0.749
Orbital inclination to planet's equator: 27.2░
Diameter: 107 mi. (172 km)
Escape velocity: ù
Magnitude: 18.7
Maximum apparent diameter as seen from the planet: 19" (ave.)
Object composition
The center of Uranus is a rocky core of heavy elements, mainly silicon and iron. Above that, an icy mantle of water, methane, and ammonia is topped by an icy "crust" of compressed hydrogen and helium that grades into atmosphere. There are no clear distinctions between the layers and no surface features on the planet.
By comparison, Neptune is composed of heavier elements than Jupiter or Saturn. While more massive than Uranus, Neptune has only 6 percent the mass of Jupiter.
[Rick: Here are the composition figures we found. You might want to compare these to figures you have.]
Core=15,000 - 16,000 km in diameter
Transition layer (mantle) =49,500 km thick
Crust = 35,000 km thick
Topography
Neptune has no distinct topographical features.
Atmosphere
Like the other giant planets, Neptune has a gaseous hydrogen and helium upper layer over a liquid interior. Its blue appearance is due to the presence of methane, which absorbs light in the red and near-infrared wavelengths. Neptune's atmosphere also appears to contain a haze of aerosol particles or ice crystals, the exact composition of which is unknown.
The highest wind speeds of any planet 2,400km (1,500 miles) per hour occur on Neptune. The mean temperature on there is -353░F / -196░ C / 76.7░ K.
The atmosphere on Neptune contains a constant feature known as the Great Dark Spot, a circular storm the size of Earth that resembles Jupiter's Great Red Spot. The spot spins counter-clockwise and moves west at almost 1,200 km (745 miles) per hour.
Magnetic fields and gravity
Neptune's magnetic field is tilted relative to its spin axis. Researchers theorize that the field is being generated somewhere above the core, where the pressure is so great that liquid hydrogen assumes the electrical properties of a metal.
The surface gravity of Neptune is 1.22.
Orbit and rotation
Neptune takes 164.8 years to complete one journey around the Sun. Though a lack of surface detail hinders precise calculation, the equatorial rotation period is believed by some astronomers to be 16 hours. Others believe it to be closer to 22 hours.
Moons and/or rings
For many years, there were only two known satellites: Triton and Nereid. In 1987, Voyager 2 provided proof of the existence of 6 more.
Triton, by far the largest moon, has a diameter between 6,000 and 7,000 km. (Nereid, the next largest, has a diameter of approximately 500 km.) Triton circles Neptune in a retrograde (backward) orbit and a has tenuous methane atmosphere. The ice caps on Triton are the coldest surface yet found in the solar system (-391░ F / -235░ C / 2░ K). Researchers note that tidal forces on Triton are causing it to spiral toward Neptune. They predict that in 10 to 100 million years, the moon will be so close that Neptune's gravity will tear it apart.
Voyager 2 confirmed the existence of the arcs of metallic material surrounding the planet. It was later determined that the arcs were, in fact, thin rings surrounding the planet.
Mythology
Neptune is named for the Roman god of the sea, and its astronomical symbol is a trident.
Discovery and exploration
Neptune was the first planet to be discovered through mathematical calculation. Its position was predicted in 1845 by English astronomer John Couch Adams and Urbain Jean Joseph LeVerrier of France. In 1846, the planet was identified by Johanne Galle and Heinrich D'Arrest in Berlin. (Both Adams and LeVerrier, however, are credited with the discovery.) Triton was discovered by William Lassell in 1846. Nereid was discovered by G. P. Kuiper in 1949. Modern-day exploration of Neptune was conducted in 1989 by Voyager 2, which came within 4,850 km (3,010 miles) of the planet on August 25.
[Rick: No data found on early belief in life forms.]
