| Neptune Facts Table |
Mass (1024 kg ):
Volume (1012 km^3):
Equatorial Diameter (km):
Polar Diameter (km):
Age of the Planet:
|4.5 billion years|
Number of Moons:
Surface Temperature Range :
|(-218 °C ~ -198 °C)|
Average Surface Temperature:
Day Length (hours):
Average Distance from Sun (106 km):
Closest Distance to Sun (Perihelion) (106 km):
Furthest Distance from Sun (Aphelion) (106 km):
|27,904.1 million km|
Orbiting velocity (km/h):
Time to Orbit the Sun (Orbital Period):
|163.7 Earth's year|
Axial Tilt Angle (degrees):
Time for Sunlight to the planet:
|4 hours, 10 minutes|
Eight planets away from the Sun, a cold, dark, and icy world exists. That world is known as planet Neptune. This mysterious, bright blue planet revolves at the outer edges of our solar system, making it the most distant as well as one of the most intriguing. Invisible to the naked eye, Neptune remained unbeknownst to our ancestors until 1846 when Urbain Le Verrier and Johann Galle discovered it. Even though year on Neptune is equivalent to 165 years on Earth, Neptune experiences seasonal changes that are very similar to those on Earth. However, each season that transpires on Neptune lasts for 41 Earth years.
Keep reading to learn about the most fascinating mysteries of Neptune.
1. Neptune, originally forming in close proximity to the Sun, migrated to the outer solar system over a time span of 500 million years.
Neptune came into existence 4.5 billion years ago when gravity pulled swirling gas and dust together to form this icy, azure planet. Though Neptune is currently the farthest planet from the Sun, scientists postulate that Neptune’s original location was in much closer proximity to the center of our universe. Only over time did it make its way to the outer solar system to its present location like its neighbor, Uranus.
2. Neptune’s illuminated surface is 900 times dimmer than that of Earth’s.
Neptune is located at a distance of 30 AU (astronomical units) away from the Sun (for reference, this distance is 30 times greater than that between Earth and the Sun). As a result, if we were to visit Neptune when it was fully illuminated by the Sun, what we would witness would seem more like dim twilight to us rather than the bright high noon we are accustomed to on Earth.
3. Winds on Neptune are powerful enough to break Earth’s sound barrier.
At high altitudes, wind speeds on Neptune can reach up to 1,200 mph (2,000 km/h). The winds on Neptune are so fast that they are capable of breaking the sound barrier: on Earth, the speed of sound equals 761.2 mph (1,225 km/h), 1.5 times slower than the turbulent winds of Neptune.
4. A day on Neptune lasts for 16 hours.
The planet of Neptune completes a full spin or rotation around its axis (one day) once every 16 hours.
5. Sunlight takes 4 hours, 9 minutes, and 55 seconds to reach Neptune.
Neptune is located 2,793 million miles (4,495.1 million km) away from the Sun (on average). Moving at a speed of 0.186 million miles/s (0.3 million km/s), sunlight needs an average of 14,995 seconds, or 4 hours, 9 minutes, and 55 Seconds, to reach Neptune.
– At Perihelion (the point at which Neptune is at its closest position to the Sun), the distance between the Sun and Neptune equals 2,761.7 million miles (4,444.5 million km), making it so that sunlight requires 14,826 seconds (4 hours, 7 minutes, and 6 Seconds) to reach Neptune’s surface.
– At Aphelion (the point at which Neptune is at its farthest position from the Sun), the distance between the Sun and Neptune equals 2,824.6 million miles (4,545.7 million km), making it so that the sunlight requires 15,163 seconds (4 hours, 12 minutes, and 43 Seconds) to reach Neptune’s surface.
But, no matter where Neptune is in its orbit, sunlight requires a relatively long time to reach it: while it takes 4 hours, 7 minutes, and 6 seconds to 4 hours, 12 minutes, and 43 seconds for sunlight to reach the surface of Neptune, depending on its position relative to the Sun, in contrast, it only takes an average of 8 minutes and 20 seconds for sunlight to reach the surface of our home planet: Earth.
6. One year on Neptune is equivalent to 165 years on Earth.
As Neptune is the farthest planet from the Sun (maintaining a distance of 2,793 million miles (4,495.1 million km) from the Sun, on average), it also has the longest orbit out of all of the eight planets in our solar system. Orbiting the Sun at a velocity of 12,080 mph (19,440 km/h), it takes Neptune around 165 Earth years to complete just a single revolution.
7. Sometimes Neptune is farther from the Sun than dwarf planet Pluto.
Dwarf planet Pluto’s orbit has a high level of eccentricity, meaning that its orbit significantly deviates from a perfectly circular one. Pluto’s elongated path around the Sun mimics the shape of an oval. Though Pluto is the farthest planet from the Sun, due to its highly eccentric, elliptical orbit, its orbit occasionally crosses into the path of Neptune’s orbit, effectively taking Neptune’s place as the eighth planet from the Sun for 20 years out of every 248 years (when measured in Earth years).
If Neptune and Pluto are repeatedly crossing into one another’s orbits, you may be wondering how they have not yet bumped into each other. Studies conducted by NASA have revealed that Pluto can, in fact, never collide with Neptune. The reason? For every three laps Neptune completes around the sun, Pluto only accomplishes two. This consistent pattern prevents the two outermost planets of our solar system from ever becoming close enough to one another to produce an accident of astronomical proportions.
8. Like Earth, Neptune experiences seasons – however, each season lasts around 41 Earth years.
Like Earth and Mars, Neptune has an axial tilt angle of 28.32 degrees. Such a tilt means that Neptune also experiences four seasons – similar to our home planet, Earth. Unlike Earth, however, as one year on Neptune lasts for 165 Earth years, each season on Neptune takes around 41.25 to complete.
9. Neptune has an Earth-sized solid core.
10. Neptune gets its bright blue color from methane gas.
Like Uranus, Neptune is rich in methane gas. As sunlight journeys through Neptune’s atmosphere, methane gas absorbs the red portion of light, leaving the planet with an intense and vibrant blue color. Though the methane gas present in Neptune’s atmosphere has been found to be largely responsible for producing Neptune’s recognizable color, NASA proposes that there might be an additional unknown component in Neptune’s atmosphere that heightens the color’s level of intensity.
11. Neptune is the windiest planet in the solar system.
The wind speeds on Neptune can reach more than 1,240 mph (2,000 km/h). Want a better idea of just how fast this is? Hurricane Patricia, a category 5 hurricane, is the most intense tropical cyclone to have ever been recorded in human history. Its peak wind speed measured at 215 mph (346 km/h), which is strong enough to destroy entire cities in only a matter of hours.
In comparison with winds observed on Neptune, Hurricane Patricia comes off as weak. Wind speeds on Neptune can climb up to an astounding 1,240 mph (2,000 km/h), which is almost 3.5 times stronger than Hurricane Patricia.
12. An oval-shaped storm known as the “Great Dark Spot” once took place on Neptune. This storm was wider than the planet Earth.
The Great Dark Spot was an oval-shaped storm that materialized in Neptune’s southern hemisphere, growing to eventually become larger than Earth. The Great Dark Spot was first observed by NASA’s Voyager 2 in 1989.
13. Neptune has 13 known moons.
Besides the 13 known moons that orbit around Neptune, there is one additional provisional moon awaiting confirmation before it attains official moon status.The largest moon revolving around Neptune is known as Triton. This moon was also the first of Neptune’s moons to be discovered. Triton was discovered by William Lassell, an amateur English astronomer and maker of telescopes, just 17 days after the discovery of Neptune itself.
14. Triton is the only moon in the solar system that orbits its planet (Neptune) in the opposite direction.
While all known moons in our solar system orbit their planets in the same direction as the planet’s rotation, Triton orbits Neptune in a retrograde rotation, meaning in the opposite direction of its planet’s rotation. Because of this, NASA hypothesizes that Triton could have once possibly been an independent object that was captured by Neptune.
15. Neptune has five known rings.
Neptune’s five rings are known as Galle, Leverrier, Lassell, Arago, and Adams, when ordered from closest to Neptune then moving outward to farthest. 
16. Neptune’s rings have peculiar clusters of dust called “arcs.”
Neptune’s outermost ring (Adams) has four prominent arcs named Liberté (Liberty), Egalité (Equality), Fraternité (Fraternity), and Courage. Scientists think that the four prominent arcs clump together rather than spread away due to the effects of Galatea’s (one of Neptune’s moons) gravity.
17. Neptune’s magnetic field is about 27 times more powerful than Earth’s magnetic field.
Below, an image produced by NASA exhibits Neptune’s magnetosphere:
Interested in learning more? Make sure to check out “How do magnetic fields protect planets from harmful space radiation?”