101 Facts About Neptune

Neptune may be the furthest planet from the Sun, but it has the most powerful wind speeds out of all 8 planets, putting Earth’s fastest tornadoes to shame. It’s also the fourth largest celestial body in our Solar System and the smallest of the gas giants. The cool thing is, Neptune was discovered purely by mathematical predictions in 1846. Curious for more interstellar facts? Keep on reading to learn 101 facts about Neptune. 

Fact 1: The total volume of Neptune is about 6.254×1013 km3. Written out in full, that number looks like this: 62,540,000,000,000 km3

Fact 2: The total mass of Neptune, all the physical stuff that makes the planet, is 1.02413×1026 kg. Now, that is a huge number that looks like this: 102,413,000,000,000,000,000,000,000. I told you it was big! 

Fact 3: In 2016, the Northern Great Dark Spot appeared in Neptune’s northern hemisphere and it’s nearly identical to the original Great Dark Spot which is a huge storm in the southern hemisphere.

Fact 4: Its rings are named after the astronomers who made an important discovery regarding the planet.

Fact 5: The first name suggested for the planet came from Johann Gottfried Galle, a German astronomer,  who proposed the name “Janus”.

Fact 6: Because of Neptune’s pronounced axial tilt, it experiences seasons just like Earth does.

Fact 7: Neptune has 5 rings orbiting it.

Fact 8: Just 17 days after the discovery of Neptune, William Lassell, an English merchant and astronomer, discovered Neptune’s largest moon, Triton. 

Fact 9: Most languages across the world today use some variant of the name “Neptune” for the planet.


Fact 10: Neptune’s core temperature sits at a nice and toasty 5,150 °C. That’s over 3 times higher than the temperature needed to melt Iron which liquifies at 1,538 °C.

Fact 11: In England, James Challis, an English physicist and astronomer, put forward the name “Oceanus” for the planet’s name.

Fact 12: Triton, Neptune’s largest moon, is 5,420 km in diameter. 

Fact 13: Neptune’s axial tilt compared to its orbit is 28.32°. This is only 4.82° more than Earth’s axial tilt. 

Fact 14: Neptune has the fastest wind speed out of all the planets.

Fact 15: Neptune’s escape velocity, the velocity of a body, such as rocket, needs to achieve to escape Neptune’s gravitational pull forever if it doesn’t have continuous thrust, is 23.5 km/s. For comparison, Earth’s escape velocity is less than half that at 11.186 km/s. “

Fact 16: Neptune’s aphelion, the farthest distance it moves away from the Sun during its orbit, is a huge 4.54 billion km. This is 33.3 times further away than Earth is from the Sun. If you decided to drive that distance in a car traveling at an average speed of 100km/h, it would take you over 5,182 years to get there! 

Fact 17: The difference between Neptune’s Equatorial diameter and polar diameter is 846 km. This gives Neptune a very obvious squashed ball appearance. 

Fact 18: Until now, the only spacecraft to visit Neptune is NASA’s Voyager 2 probe. 

Fact 19: It is the only planet that’s not visible from Earth with the unaided human eye.

Fact 20: The tail of Neptune’s magnetosphere extends back behind the planet away from the Sun 36 times its own diameter.

Fact 21: It has been suggested that giant diamond ice-bergs float on a sea of liquid diamond on Neptune’s core-mantle boundary. 

Fact 22: Wind speeds blowing westward on the planet’s equator reach up to 2,160 kilometres per hour. 

Fact 23: Neptune has 14 known moons.

Fact 24: Argo is a proposal for a flyby spacecraft that would visit Jupiter, Saturn, Neptune, and a Kuiper belt object.

Fact 25: Neptune is slightly denser and more massive than it’s near-twin Uranus. However, its large mass causes more gravitational compression in its atmosphere, making Neptune physically smaller than Uranus.

Fact 26: Since Neptune was the last major planet that the Voyager 2 spacecraft could visit, NASA decided to make a close flyby of the moon Triton. The images relayed back to Earth from Voyager 2 became the basis of a 1989 PBS all-night program, “Neptune All Night”.

Fact 27: Neptune’s polar diameter is 48,682 km. For comparison, Earth’s polar diameter is 12713.6 km.

Fact 28: Neptune’s first planetary ring was discovered by Edward Guinan in 1968.


Fact 29: Galileo actually observed Neptune multiple times two hundred years before it was officially discovered. The first time was on 28th December, 1612, and the second time on 27th January, 1613. However, he thought the planet was a star, so he is not credited with its discovery. 

Fact 30: Neptune’s perihelion, the closest approach it makes to the Sun on its orbit, is 4.46 billion km. That’s just under 30 times farther away from the Sun than Earth is from the Sun. If you decided to get a little fitter and jog to Neptune, you better pack a sizable lunch as it’s going to take you a while to get there! At a constant jogging speed of 8km/h it would take you 63,642 years, yes years, to jog your way to Neptune. 

Fact 31: In modern Greek the planet Neptune is called Poseidon. 

Fact 32: Like its neighbour Uranus, Neptune likely formed closer to the Sun and moved to the outer Solar System about 4 billion years ago.

Fact 33: Some unknown atmospheric compound must contribute to Neptune’s blue color, otherwise it would be the same green color as Uranus.

Fact 34: The Great Dark Spot, a storm on the surface of Neptune, is dark because it is literally a shallow hole cutting down into the atmosphere of Neptune.This gives it a dark appearance as it is slightly recessed from the rest of the atmosphere. 

Fact 35: The average diameter across the planet is 49,244 km. Almost 4 times the diameter of Earth.

Fact 36: Neptune is 17 times the mass of Earth.

Fact 37: Neptune’s equatorial diameter is 49,528 km. That’s nearly 4 times Earth’s diameter which sits at 12,742 km. 

Fact 38: The composition of Neptune’s atmosphere by volume is:

80% hydrogen, 18% helium, 2% methane, hydrogen deuteride, and ethane.”

Fact 39: Shortly after it’s discovery, Neptune was called “Le Verrier’s planet”.

Fact 40: Some scientists have hypothesized that billions of years ago, Neptune was much bigger with a far thicker atmosphere. However, a passing star blasted off Neptune’s thick atmosphere leaving behind the smaller planet we see today. 

Fact 41: It was named after the Roman God of the Sea.

Fact 42: There has been a proposal by NASA’s “Vision Missions Studies” for a “Neptune Orbiter with Probes” mission.

Fact 43: Most of Neptune’s winds travel retrograde to the rotation of the planet, and are 5 times stronger than the strongest winds recorded on Earth.

Fact 44: Ever since the disqualification of Pluto as a planet, Neptune is considered the coldest planet with an average temperature of -200o.

Fact 45: The known moons are named Naiad, Thalassa, Despina, Galatea, Larissa, S/2004 N1, Proteus, Triton, Nereid, Halimede, Sao, Laomedeia, Psamathe, and Neso.

Fact 46: Neptune was the name that ancient Romans gave to the Greek God of the Sea and earthquakes, Poseidon. He was the brother of Jupiter (Zeus) and of Pluto (Hades).

Fact 47: Its atmosphere has traces of hydrocarbons and possibly nitrogen, though it contains a higher proportion of “ices” such as water, ammonia, and methane.

Fact 48: Neptune’s core is mostly made of iron and nickel with a few silicate compounds thrown in. 

Fact 49: Like Jupiter and Saturn, Neptune’s atmosphere is made up from mainly helium and hydrogen.

Fact 50: High internal heating causes the extreme weather found on Neptune.

Fact 51: Neptune was officially discovered in 1846 by Johann Galle.


Fact 52: Neptune’s Atmosphere, at a depth of 1 Bar (1 Earth atmospheric pressure at sea level) is approximately 20km. 

Fact 53: In Japanese, Korean, Chinese, and Vietnamese, the planet’s name is translated as “sea king star” (海王星).

Fact 54: NASA’s Voyager 2 probe flew past the giant planet in 1989. 

Fact 55: Neptune has over 17 times Earth’s mass. That means if you could place Neptune on a cosmic sized weighing scale, you’d need 17 Earths just to balance it out. 

Fact 56: Triton is the largest among the 14 moons.

Fact 57: Crystals of diamond rain down like hailstones through the Neptunian Mantle at depths of 7000 km.

Fact 58: Neptune is the fourth-largest planet by diameter in the solar system. In order of physical size, Neptune comes after Jupitar, Saturn, and Uranus. 

Fact 59: Neptune makes a full revolution around the Sun every 164.8 Earth years.

Fact 60: Neptune’s rings are far more unstable than previously thought. In the time between Voyager 2’s fly by and the early 2000s, Neptune’s rings had substantially decayed. 

Fact 61: Neptune has 58 times Earth’s volume. Yes, that means you could squash 58 Earths inside Neptune. 

Fact 62: Urbain Le Verrier, the French astronomer and mathematician who predicted Neptune’s existence using math, claimed the right to name his discovery Neptune. Soon Neptune became the internationally accepted name.

Fact 63: Neptune is the densest giant planet in our Solar System, and is the 5th densest planet over all after Earth, Mercury, Venus, and Mars. 

Fact 64: Neptune’s surface gravity is measured at 11.15 m/s2. For comparison, Earth’s surface gravity is only a little less at 9.807 m/s². 

Fact 65: It is thought that some of Neptune’s rings may disappear entirely in as little as a century. 

Fact 66: Neptune has a faint and fragmented ring system that was first discovered in 1984.

Fact 67: It takes 13 years for Neptune to move through each constellation of the zodiac.

Fact 68: In 2011, it completed its first full orbit of the Sun since being discovered and returned to where it was first spotted 2° northeast of Iota Aquarii.

Fact 69: Neptune is the third-most-massive planet in the Solar System behind Jupiter and Saturn.


Fact 70: The speed at which Neptune’s Equator rotates is 2.68 km/s. For comparison, Earth’s equatorial rotational velocity is 0.46 km/s. 

Fact 71: Neptune radiates about 2.61 times the amount of energy that it receives from the Sun.

Fact 72: Neptune’s active weather patterns were evident during Voyager 2’s flyby in 1989, which revealed Neptune’s Great Dark Spot located on the planet’s southern hemisphere.

Fact 73: Neptune’s atmosphere is made up of hydrogen, helium and methane. The methane in Neptune’s upper atmosphere absorbs the red light from the sun but reflects the blue light back into space.

Fact 74: Neptune wasn’t always the furthest planet from the Sun. Pluto held the spot as the 9th planet in the Solar System for many years until Pluto lost its planet status and became a dwarf planet.

Fact 75: Its discovery sparked a heated nationalistic rivalry between the Brits and the French over who deserved credit for the planet’s discovery.

Fact 76: The average density of Neptune is 1.638 g/cm3. This is over 3 times less than the density of Earth.

Fact 77: The total surface area of Neptune is 7.6183×109 km2. In full that number looks like this: 7,618,300,000 km2. That’s about 775 times the surface area of the United States of America. 

Fact 78: A mantle of liquid electrically conductive water, ammonia, and methane gives rise to Neptune’s magnetosphere. 

Fact 79: The great Dark Spot, a storm on the surface of Neptune, was over 13,000 km wide and 6,600 km high when first observed. That is just a little wider than the planet Earth! 

Fact 80: Neptune’s seasons last for forty Earth years.


Fact 81: Neptune’s average orbital speed around the Sun is 5.43 km/s. For comparison, that’s way faster than the world’s fastest ever air-breathing aircraft, the Lockheed SR-71 Blackbird, which, at top speed, could travel at 1 km/s.

Fact 82: Unlike its near-twin Uranus, Neptune’s atmosphere has active and visible weather patterns.

Fact 83: Every 248 years, Pluto crosses Neptune’s orbit and moves closer to the Sun. This is because Pluto has a very elliptical (Flattened circle) orbit that brings it inside Neptune’s orbit. 

Fact 84: Neptune is the eighth, and farthest known planet from the Sun in the Solar System.

Fact 85: Neptune’s day is 16 h 6 min 36 seconds long.

Fact 86: Neptune is over 50% farther from the Sun than Uranus. As a result of this difference in distance Neptune receives only 60% less sunlight than Uranus. 

Fact 87: It has the astronomical symbol ‘♆’, which looks a lot like the trident used in the film Aquaman!

Fact 88: This ice giant has a bright azure blue color.

Fact 89: Neptune’s average distance from the Sun is 4.50 billion km. That is about 30 times the distance that Earth orbits from the Sun. This 4.5 billion km may sound like a lot but actually, in astronomical terms, it’s a small distance when compared to the distance to the nearest star which is 8889 times further away!  

Fact 90: Neptune took shape when the rest of the Solar System formed about 4.5 billion years ago.

Fact 91: Neptune’s faint and fragmented ring system consists of a number of arcs that are broken up from each other. 

Fact 92: Neptune’s apparent magnitude, the ease at which the naked eye can see a space object from Earth, is +7.67 to +8.00. The naked eye can’t see anything with an apparent magnitude of more than +6.5.

Fact 93: Neptune’s five rings are: Galle, Le Verrier, Lassell, Arago, and Adams.

Fact 94: The adjective used for Neptune is the word ‘Neptunian’. 

Fact 95: A Neptunian year is 89,666 Earth days long. That’s a long time to wait between birthdays!  


Fact 96: Neptune’s magnetosphere extends 17.5 times the planet’s diameter toward the Sun. 

Fact 97: Scientists have been surprised to learn that Uranus actually reaches colder temperatures on occasions despite the fact that Neptune, on average, is colder than Uranus. Plus neptune is further away from the Sun than Uranus.

Fact 98: Neptune’s mantle is 10 to 15 Earth masses in size.

Fact 99: The planet Neptune was mathematically predicted before it was directly observed.

Fact 100: Triton is the 7th largest known moon in the Solar System.

Fact 101: Neptune’s magnetosphere is offset from the planet’s centre by nearly 13,500 km. That’s over half the planet’s radius. Scientists don’t entirely understand why. But they think it has something to do with the electrically conductive mantle.    


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