When I look up into the night sky, I expect to see a lot of stars. A few planets. Often the moon. What I don’t expect to see are Greek and Roman gods – because, you know, I’m not an Ancient who thinks all-powerful deities are just floating around up there.
Yet, as I’ve discussed before in my ongoing series about the planets of our solar system, Roman and Greek mythology haunts our astronomical realities like that ghost who haunts my Aunt Martha’s house. (At least, according to Aunt Martha.)
There’s just no escaping it!
There’s a good reason for this, mostly. While the ancient peoples of the Mediterranean weren’t the first to notice our stars and planets, they were the ones whose names for them we kept. Accordingly, planetary epithets such as Mercury, Venus, Mars, Jupiter, and Saturn all represent gods of the Old World … and the same is true for Neptune.
This is one of the many neat facts about the last known planet in our solar system, a bright blue ice giant that we’ve only gotten to know in the last few centuries.
If you, like me, would like to get to know it better, I invite you to read on.
1. Neptune Was Named After the Sea God
In Ancient Greek and Roman mythology, the god of the sea was at times jovial and at times very frightening indeed.
Named Poseidon in Greek mythology and repurposed as Neptune come Roman times, the sea god was a member of the pantheon – the group of gods that made up the inhabitants of Mount Olympus.
You might recognize Poseidon from school readings of The Odyssey, where he terrorized the eponymous main character, Odysseus, for 20 years. He had a reason, of course: Odysseus blinded his son, Polyphemus. (In all fairness, Polyphemus was a cyclops who was trying to eat him and all his crew.)
Neptune’s discoverers decided to stick with the tradition of Roman names for planets, so they went with Neptune in honor of the planet’s deep blue color.
2. … and So Were Its Moons
The 14 natural satellites of Neptune were also named after characters from Greek and Roman mythology. Its largest and most recognizably moon-ish moon, Triton, was named for the son of Poseidon. You might recognize him as a merman – half man, half fish – who is variously portrayed with a conch, water horse, or sometimes trident.
Not sure what a trident is? Think the forky-looking spear that King Triton holds in The Little Mermaid. Many representations of Poseidon or Neptune also feature the god holding a trident, which has the ability to kill with one stroke.
Its other moons also bear famous names, including Galatea, Naiad, and Hippocamp.
3. Neptune’s Moon Triton Breaks the Mold
Many of the moons orbiting the giant planets are unusual and diverse. They feature geysers, canyons, oceans, and volcanoes. Some of these moons – such as Jupiter’s Europa and Saturn’s Enceladus – might even be able to support life due to their liquid water environments.
Triton is not a candidate for life, we don’t think. However, it is unique in other ways. It has ice volcanoes, for one thing, which is just cool. These spew what is thought to be liquid nitrogen, methane, and dust into its thin, frigid atmosphere, where it instantly freezes and returns to the surface as snow.
4. Neptune Is Very, Very Far Away
Although recent images and our increasing knowledge of the planet make it seem as though Neptune is a near neighbor, that’s far from the truth. The eighth planet in our solar system is very far away indeed.
On average, the planet is 2.8 billion miles away from the sun – or 4.5 billion kilometers. It is more than 30 times as far away from our home star as the Earth, so its temperatures are killingly cold.
On average, a photon from the sun will take about 4 hours to reach Neptune. That’s opposed to eight minutes to reach Earth.
5. It Takes A LONG Time to Orbit the Sun
We all know it takes a year to orbit the sun. That’s why you call your birthday “another trip around the sun.” And if you don’t, you should, because all the cool kids are saying it.
Having a bday on Neptune would be a real bummer, though, because it takes a full 165 Earth years for Neptune to orbit the sun. In one Neptunian year, you could die twice over!
Believe it or not, Neptune has only completed one full orbit of the sun since its discovery. Which, more on that below.
6. Neptune Is an “Ice Giant”
You’re probably familiar with the term “gas giant,” which many people mistakenly apply to Neptune and Uranus as well. However, these are properly termed “ice giants.”
An ice giant is a planet that is composed mostly of “ices.”
If that sounds confusing, it’s because the term “ice” is used differently by planetary scientists. Instead of meaning frozen water, it means inexact mixtures of substances such as water, methane, and ammonia, with a few other ingredients sprinkled in (a little carbon monoxide here, some nitrogen there).
Whereas Jupiter and Saturn, the gas giants, are composed mainly of gases, Neptune and its cousin Uranus are composed of ices in liquid and gaseous forms.
As you go toward the planet’s core, the contents become more pressurized, turning to liquid oceans.
Far below, at the center, Neptune has a rocky core similar in size to Earth.
7. We’re Not Quite Sure What Makes It So Blue
Neptune and Uranus seem to have mostly the same makeup. Although Neptune is a bit more dense, it has a similar methane content in its atmosphere, which can explain some of the blue color.
However, while Uranus is grey-blue, Neptune is a bright cobalt color. Theories about this include that Neptune could be darker due to evaporating hydrogen sulfide ice and because Uranus’s cloud layers vary in thickness compared to Neptune.
8. Neptune Is Not Habitable for Life … We Think
Perhaps the only thing that makes Neptune remotely like the sea after which it was named is the fact that, at the deepest depths, our oceans don’t seem much more habitable than the planet is.
Neptune is far from conducive to life, after all. It has enormous pressures at its core and is freezing cold at its “surface” – which is not even a surface at all, since it’s made of gas. Plus, compounds such as methane and ammonia are toxic to much of life as we know it.
However, even at great depths such as the bottom of the Mariana Trench, our oceans harbor specially adapted life.
Until we design probes that can actually visit the surface of Neptune, we can’t know for sure that life has not evolved to meet the extreme challenges of its inner terrain.
9. Diamond Rain Is Totally a Thing
Diamonds are relatively rare here on Earth and are consequently quite expensive. However, this may not be the case on the ice giants.
Neptune, for instance, is likely to experience “diamond rain,” just like its cousin Uranus. On these planets, extreme pressures compact carbon, forcing it to assume the regular crystalline structure that becomes diamonds. These may even aggregate into giant million-carat icebergs of diamond.
10. It Was Discovered in 1846
The age of telescopes made the discovery of Neptune possible. Too faint for the human eye to detect, it wasn’t apparent to the Ancients. However, people had good reason to believe it was there before its 1846 discovery.
“Irregularities in the orbit of Uranus led French mathematician Joseph Le Verrier and British astronomer John Couch Adams to independently calculate where an unknown body affecting Uranus might be,” explains the Smithsonian Air and Space Museum. “Using Le Verrier’s prediction, German astronomer Johann Galle found Neptune in 1946 while observing the sky at the Berlin Observatory.”
Oh, and we can thank beer for the discovery of its main moon, Triton.
“We don’t know if William Lassell had a celebratory beverage after his discovery of Neptune’s moon, Triton, but beer made the finding possible,” says NASA. “Lassell was one of 19th century England’s grand amateur astronomers, using the fortune he made in the brewery business to finance his telescopes.”
11. Neptune Looks Crazy in Infrared
Neptune is a pretty dark planet, meaning it doesn’t reflect a ton of the sun’s light. That’s why we can’t see it with our eyes and why the Ancients didn’t know about it. While we do know about it today, though, its darkness makes it hard to pick out features such as rings and moons.
That all changes if you take a picture of the planet in near-infrared though – pretty incredible, right?
12. It Has Rings!
Though nowhere near as bright and impressive as Saturn’s rings, Neptune also has rings as well as arced belts of matter orbiting it. Currently, we know of at least five rings (some say six) as well as several incomplete “arcs” or partial rings.
Although currently Neptune’s rings are relatively dark and unimpressive, at least compared to the glory of Saturn’s, there is a chance it may have such a feature in the future. Why? Because Triton has an odd orbiting pattern that is bringing it closer to the surface of the planet with every pass.
Within a few million years, it might get close enough to be torn apart – just like a primordial moon orbiting Saturn likely did.
13. It’s the Windiest Place in the Solar System
Supersonic winds populate Neptune and make it the windiest place in the solar system. Its winds move faster than the speed of sound, around 1,200 miles or 2,000 kilometers per hour. That’s nearly five times faster than on Earth, where the top speeds only hit 250 miles or 400 kilometers per hour.
14. Humanity Didn’t Go Farther Than Neptune Until 1983
Neptune formed an outer limit in our solar system for the vast majority of its history. Yes, Pluto orbited beyond it (and sometimes within it – see below). And yes, there are objects in the Kuiper Belt and Oort Cloud.
However, Neptune’s path has gone uncrossed for most of its life. That limit held until Pioneer 10 crossed the path of Neptune in 1983 on its way to the star Aldebaran. If all goes according to plan, it should pass by that star in around 2,000,000 years.
15. Humans Have Only Visited Once
The only spacecraft ever to intentionally visit Neptune was Voyager 2 in 1989. Much like Pioneer 10, it sailed on by – but not before it passed approximately 3,000 miles (4,800 kilometers) above the planet’s north pole.
16. Neptune Might Have a Neighbor Named Planet Nine
The outer edges of the solar system are weird, and we can’t explain all of the gravitational effects happening there. That has led scientists to theorize that there might be a mysterious “Planet Nine” living not too far from Neptune and playing havoc with the normal laws of space.
17. The Planet Is Four Times the Size of Earth
Neptune is about four times wider than the Earth. Its radius is about 15,300 miles or 24,600 kilometers, while Earth’s is only 3,960 miles or 6,371 kilometers. According to NASA, “If Earth were the size of a nickel, Neptune would be about as big as a baseball.”
18. It Has Seasons
Seasons are caused when a planet is tilted, meaning that at different times of the year, different parts of the planet are closer to or further from the sun.
For instance, Earth’s tilt means that the Northern Hemisphere is closer in summer and farther away from the sun in winter.
Neptune also has a tilt, so it also experiences seasons. Since it orbits the sun once each 165 Earth years, though, its seasons are about 40 years long!
19. Neptune and Pluto Do an Occasional Switcheroo
The dwarf planet Pluto usually orbits beyond Neptune. However, every once in a while, Neptune becomes the farther body when Pluto’s eccentric orbit cuts across its path and closer to the sun.
20. Its Magnetic Field Is Cuckoo
Magnetic fields are big-time important if you want to support life. Earth’s magnetosphere keeps harmful radiation away from the planet’s surface, for instance, and helps many animals migrate.
Our magnetic field is quite stable, though, because it aligns pretty well with our axis of rotation, meaning we have a north and south magnetic pole that aligns with our rotational poles.
Neptune? Not so much. Its magnetic field axis is 47 degrees off of its rotational axis, meaning its surface goes through some crazy magnetic changes throughout the day. And, since the field is 27 times more powerful than Earth, these changes are way more noticeable.
Don’t try to use a compass there, is all I’m saying.
Now Tell Everyone!
All right, now that we’ve taken a deep dive into the remarkable blue ice giant, it’s time to spread the word. Everyone deserves more recognition, and that includes this lovely celestial body.
So feel free to share everything you’ve learned here with your friends and family, use it for a school report, or check out the links above and write up your own Neptune facts! I can’t wait to see what you come up with in honor of our eighth planet.