Neptune
Pluto
Diameterkm
49,528
2,377
Mass (Earth = 1)x
17.15
0.00
Surface Gravitym/s²
11.15
0.62
Mean Temperature°C
-214
-230
Distance from SunAU
30.07
39.48
Orbital Perioddays
59,800
90,560
Day Lengthhours
16.11
153.29
Known Moons
16
5
Axial Tilt°
28.32
122.53
Orbital Velocitykm/s
5.43
4.67
Quick Facts
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.
Pluto
- -Pluto was reclassified from planet to dwarf planet in 2006 by the International Astronomical Union.
- -Pluto's largest moon Charon is so large (half Pluto's diameter) that they orbit a point between them, forming a binary system.
- -Pluto's famous heart-shaped feature, Sputnik Planitia, is a vast plain of nitrogen ice over 1,000 km across.
- -One year on Pluto takes 248 Earth years -- it hasn't completed a single orbit since its discovery in 1930.