Earth
Neptune
Diameterkm
12,742
49,528
Mass (Earth = 1)x
1.00
17.15
Surface Gravitym/s²
9.81
11.15
Mean Temperature°C
+15
-214
Distance from SunAU
1.00
30.07
Orbital Perioddays
365.25
59,800
Day Lengthhours
24.00
16.11
Known Moons
1
16
Axial Tilt°
23.44
28.32
Orbital Velocitykm/s
29.78
5.43
Quick Facts
Earth
- -Earth is the only planet not named after a Greek or Roman deity.
- -Earth's rotation is gradually slowing -- days are getting about 1.4 milliseconds longer per century.
- -About 71% of Earth's surface is covered by water, but 96.5% of that water is in the oceans.
- -Earth's magnetic field has flipped its polarity hundreds of times over millions of years.
Neptune
- -Neptune has the strongest winds in the solar system, reaching speeds of up to 2,100 km/h.
- -Neptune was the first planet discovered through mathematical prediction rather than observation.
- -One year on Neptune lasts about 165 Earth years -- it has completed just one orbit since its discovery in 1846.
- -Neptune's moon Triton orbits backward (retrograde), suggesting it was captured from the Kuiper Belt.