Neptune facts – orbit, physical overview, natural satellites, etc

Neptune is the eighth and last planet from the Sun. It is the fourth-largest planet by diameter but the third heaviest after Jupiter and Saturn. Let’s learn some interesting facts about Neptune, the “blue planet“.

Facts about Neptune (everything you need to know)


  • Neptune orbits at a distance of 2.8 billion miles (average) from the Sun. 2.8 billion miles is approximately equal to 30 Astronomical Units (AU). 1 Astronomical Unit is the average distance of Earth from the Sun. In other words, the distance of Neptune from the Sun is 30 times the distance of Earth from the Sun.

2.8 billion miles = 4.5 billion kilometers

  • Neptune takes 60,190 Earth days to complete one revolution around the Sun.

1 Neptune year = 164.79 Earth years

  • Neptune takes only 16 hours to complete one rotation around its axis.

1 Neptune day = 0.67 Earth days

An image of Neptune

Physical Overview of Neptune

  • Water, methane, and ammonia make up more than 80% of the planet’s mass. These compounds are present in a hot, dense fluid state.
  • In planetary science compounds with a melting point above 100 Kelvin are known as “ices”. Since water, methane, and ammonia have melting points above 100 kelvin, Neptune is known as an “ice giant“. The other ice giant is Uranus.
  • Neptune’s upper atmosphere is mostly made up of hydrogen and helium with a small amount of methane.
  • There is no true surface at Neptune. There is a small rocky core about the size of Earth.
  • Neptune is about 4 times wider than Earth.

Mean radius of Neptune = 24,622 km
Mean radius of Earth = 6,371 km

  • Neptune is about 17 times heavier than Earth.

Mass of Neptune = 102.413 * 10^24 kg
Mass of Earth = 5.9724 * 10^24 kg

  • Neptune is the densest of all giant planets. Still, its average density is even less than one-third of Earth’s average density.

Neptune’s average density = 1,638 kg / m3
Earth’s average density = 5,514 kg / m3

Rings of Neptune

All giant planets have rings around them. There are 5 main rings of Neptune. These are named Galle, Le Verrier, Lassell, Arago, and Adams. The rings are mostly made of dust and the material is extremely dark.

Along with 5 main rings, there are 4 dust arcs named Fraternité, Égalité, Liberté, and Courage. These arcs are present in the outermost ring Adams.

Image of Neptune and its rings
Rings of Neptune

Natural satellites of Neptune

There are 16 known moons of Neptune. Triton is the largest moon of Neptune. It is also the seventh-largest moon in our solar system.

Triton is the only large moon in our solar system that has a retrograde orbit. It means it orbits in the opposite direction of Neptune’s rotation.

Neptune vs Earth comparison

Radius24,622 km (15,299.4 miles)6,371 km (3,959 miles)
Mass102.413 * 10^24 kg5.9724 * 10^24 kg
Planet typeGas/Ice giantTerrestrial
Position from the Sun8th3rd
Number of moons161
Day lengtharound 16 hoursaround 23.9 hours
Year length165 Earth years365.25 days
Time taken by sunlight to reacharound 4.1 hours8 minutes 20 seconds
Average distance from the Sun4.5 billion kilometers (2.8 billion miles)150 million kilometers (93 million miles)
Ring systemYesNo

Additional facts about Neptune

  • Neptune was named after the Roman god of the seas.
  • Neptune is the windiest planet in our solar system, with wind speeds exceeding 1,200 miles per hour (2,000 km/hr) in some places.
  • Voyager 2 is the only spacecraft that has visited Neptune.
  • Neptune’s rotational axis is tilted at an angle of 28.32 degrees with respect to its orbital axis.

Quick question

Which is the densest planet in our solar system?

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Answer to quick question

Earth is the densest planet in our solar system with a mean density of 5,514 kg / m3. Mercury is the second densest with a mean density of 5,427 kg / m3.

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