Neptune

海王星

Mass (Earth=1) 质量（地球=1）	17.2
Equatorial diameter (km) 赤道直径（公里）	49,500
Period (years) 周期（年）	165
Mean distance from Sun, 10^6 km 到太阳的平均距离，10^6 km	4,500
Density (water=1) 密度（水=1）	1.67
Surface gravity m/s^2 表面重力 m/s^2	11.0

Moons

卫星

Neptune is a near twin of Uranus in size, one of the gas giants.

海王星在大小上接近天王星，是气态巨行星之一。

Neptune was discovered mathematically before it was seen telescopically. The varying orbital speeds of Uranus allowed J.C. Adams and J. J. Leverrier to calculate in 1845 that an unknown planet was affecting Uranus gravitationally. In 1846, J. Galle found Neptune where the mathematicians predicted it.

海王星是在望远镜观测之前被数学计算发现的。天王星轨道速度的变化使J.C.阿德斯和J.J.勒维耶在1845年计算出有一个未知行星正在引力上影响天王星。1846年，J.加勒在数学家预测的位置发现了海王星。

Planetary data

行星数据

Neptune's Moons

海王星的卫星

Triton has a retrograde orbit, moving clockwise around the planet Neptune while most other bodies in the solar system revolve counterclockwise. It may host what would be the only known liquid-nitrogen ocean.

特拉يون的轨道是逆行的，它围绕海王星顺时针旋转，而太阳系中大多数其他天体则是逆时针旋转。它可能拥有已知唯一液态氮海洋。

Nereid has a highly eccentric orbit, taking it 1.4 million to 9.7 million kilometers from Neptune. Nereid was discovered in 1949. The color of Nereid is unlike any normal satellite or asteroid, varying in reflected intensity by a factor of four during 1987 observations. This may mean it is irregular in shape, but its estimated diameter of 660 km is over the threshold of about 400 km which is thought to be enough to make objects spherical. Because of its eccentric orbit, Nereid may be a captured asteroid. ( Weisburd, Science News 133, June 11, 1988 p374)

Nereid有高度偏心的轨道，使其与海王星的距离从140万公里到970万公里不等。Nereid于1949年被发现。Nereid的颜色不同于任何正常的卫星或小行星，在1987年的观测中，其反射强度变化了四倍。这可能意味着它的形状不规则，但其估计直径为660公里，超过了约400公里的阈值，这个阈值被认为足以使天体呈球形。由于其偏心轨道，Nereid可能是一颗被捕获的小行星。（Weisburd, Science News 133, June 11, 1988 p374）