Neptune

Neptune

Orbital characteristics

Semi-major axis

4,498,252,900 km
30.068 963 48 AU

Eccentricity

0.008 585 87

Orbital period

60,224.9036 d
(164.89 a)

Synodic period

367.49 d

Avg. Orbital Speed

5.432 km/s

Inclination

1.769 17°
(6.43° to Sun's equator)

Number of satellites

Physical characteristics

Equatorial diameter

49,528 km [1]
(3.883 Earths)

Surface area

7.619×109 km2
(14.937 Earths)

Mass

1.0243×1026 kg
(17.147 Earths)

Mean density

1.638 g/cm3

Equatorial gravity

11.00 m/s2
(1.122 gee)

Escape velocity

23.5 km/s

Rotation period

0.671 250 00 d (16 h 6 min 36.000 00 s) 1

Rotation velocity

2.68 km/s = 9660 km/h (at the equator)

Axial tilt

28.32°

Albedo

0.41

Surface temp.

min	mean	max
50 K	53 K	N/A K

Atmospheric characteristics

Atmospheric pressure

100-300 kPa

Hydrogen

>84%

Helium

>12%

Methane

Ammonia

0.01%

Ethane

0.00025%

Acetylene

0.00001%

Neptune is the eighth planet from the Sun, and the outermost gas giant in our solar system.

Due to Pluto’s eccentric orbit, Neptune is sometimes the furthest planet from the Sun. Orbiting so far from the sun, Neptune receives very little heat. Its surface temperature is −218 °C. However, the planet seems to have an internal source of heat. Neptune's atmosphere has the highest wind speeds in the solar system, up to 2000 km/h.