Neptune sits so far away that most people can barely picture it. It’s that distant blue dot that even NASA took decades to reach. And yet, this cold, windy planet has a whole family of moons orbiting it.
But how many people actually know their names?
Most can name the Moon. Some can name a few of Jupiter’s. Saturn’s moons get a mention every now and then. Neptune’s moons, though? They almost always get left out of the conversation.
This blog covers all the known moons of Neptune, their names, a little about each one, and what makes them worth knowing about.
How Many Moons Does Neptune Have?
Neptune has 16 confirmed moons. That number might surprise people who pictured it as just a cold, distant planet with nothing much happening around it.
These moons vary quite a bit. Some of them are large and well-studied.
Some are tiny, oddly shaped, and were only spotted recently with powerful telescopes. They all orbit Neptune, but not all of them move in the same direction or at the same speed.
Triton, the largest, was found on October 10, 1846, just 17 days after Neptune itself was spotted by astronomers.
The two most recent moons, S/2002 N5 and S/2021 N1, were confirmed in 2024 by Carnegie Science, proving that this distant planet still holds surprises
Names of Neptune’s Moons
Neptune’s known moons each have a unique story. Here is a closer look at all of them.
1. Triton
Image Source: NASA Science
Triton is Neptune’s largest moon and, honestly, the most talked-about one. It was discovered on September 10, 1846, just 17 days after Neptune itself was found.
What makes Triton stand out is that it orbits Neptune backwards. That kind of reverse orbit strongly suggests it was captured from elsewhere in space, rather than forming alongside Neptune.
It also has active geysers that shoot nitrogen gas miles into the air.
2. Nereid
Image Source: Wikipedia
Nereid was discovered in 1949 and holds the record for one of the most stretched-out orbits of any moon in the solar system.
It takes about 360 days to complete just one trip around Neptune. For a long time, Nereid and Triton were the only known moons of Neptune.
Not much is known about its surface, but its odd orbit has kept scientists curious about its origin for decades.
3. Naiad
Image Source: Wikipedia
Naiad is the closest moon to Neptune and moves incredibly fast because of it. It completes one full orbit in less than eight hours.
Discovered during Voyager 2’s flyby in 1989, Naiad is small and irregularly shaped. It sits so close to Neptune that it actually orbits inside the planet’s ring system.
Scientists believe its orbit has been slowly shifting over time, which makes it one of the more interesting smaller moons to study.
4. Thalassa
Image Source: Wikipedia
Thalassa was also discovered during Voyager 2’s 1989 flyby. It is a small, flat moon that orbits just outside Naiad.
Like its neighbor, Thalassa moves quickly and sits very close to Neptune. Its name comes from the Greek word for sea. The moon is irregularly shaped and quite dark.
It is considered an inner moon and helps shape some of Neptune’s faint rings through gravitational interactions.
5. Despina
Image Source: Wikipedia
Despina is another inner moon found during the Voyager 2 mission. It orbits Neptune closer than Larissa but farther out than Thalassa.
Despina is notable because it acts as a shepherd moon, meaning its gravity helps keep one of Neptune’s rings in place. It is small and dark, much like the other inner moons.
Named after a daughter of Neptune in Greek mythology, Despina completes one orbit around the planet in roughly eight hours.
6. Galatea
Image Source: Wikipedia
Galatea sits just inside Neptune’s Adams ring, the most prominent of Neptune’s rings.
Its gravity plays a key role in keeping that ring together, making it another shepherd moon. Galatea was discovered by Voyager 2 in 1989. It has an irregular shape and a dark surface.
The moon completes one orbit in roughly 10 hours. Named after a sea nymph from Greek mythology, Galatea is small but has a meaningful gravitational influence on the ring system around it.
7. Larissa
Image Source: Wikipedia
Larissa was actually spotted briefly in 1981 during a ground-based observation, but its confirmation as a moon came through Voyager 2 in 1989.
It is one of the slightly larger inner moons of Neptune. Larissa has an irregular, cratered surface and orbits Neptune every 13 hours or so. Its surface shows signs of past impacts.
Named after a nymph in Greek mythology, Larissa remains one of the better-studied inner moons despite being relatively small.
8. Hippocamp
Image Source: Wikipedia
Hippocamp is the most recently confirmed inner moon of Neptune, identified in 2013 using images from the Hubble Space Telescope. It is tiny; only about 34 kilometers across.
Scientists believe it may have broken off from Proteus after an ancient impact.
Hippocamp orbits very close to Proteus and is hard to spot because of how small and faint it is. Its discovery showed that even well-studied planets can still hold surprises closer to home.
9. Proteus
Image Source: Wikipedia
Proteus is Neptune’s second-largest moon and was discovered by Voyager 2 in 1989.
It is so dark that it reflects very little light, which is why it went unnoticed for so long despite its size. Proteus is irregularly shaped and heavily cratered. It orbits Neptune in roughly 27 hours.
Scientists believe it sits right at the size limit where a moon’s gravity would normally pull it into a rounder shape, making it an interesting case for planetary scientists.
10. Halimede
Image Source: Wikipedia
Halimede is one of Neptune’s outer irregular moons, discovered in 2002 using ground-based telescopes.
It orbits Neptune at a much greater distance than the inner moons and takes several years to complete one full orbit. Halimede moves in a retrograde direction, meaning it orbits opposite to Neptune’s rotation.
Some researchers think it may share an origin with Nereid, possibly from an ancient collision. Named after a sea nymph, Halimede remains poorly understood due to its distance and small size.
11. Sao
Image Source: NASA Science
Sao is a small outer moon discovered in 2002. It follows a prograde orbit, meaning it moves in the same direction as Neptune’s rotation.
Sao sits far from Neptune and takes several years to complete a single orbit. Not much detail is known about its surface or exact composition.
Like most of Neptune’s outer moons, it is thought to be a captured object. It is named after a sea nymph from Greek mythology, keeping with Neptune’s ocean-themed naming pattern.
12. Laomedeia
Image Source: Wikipedia
Laomedeia is another outer moon found in 2002. It also follows a prograde orbit around Neptune. It is small, distant, and not well studied.
Like Sao, it takes years to complete one orbit and is believed to be a captured body rather than one that formed in place. Laomedeia is named after one of the 50 Nereids, sea nymphs from Greek mythology.
Its discovery came as part of a broader survey that added several new outer moons to Neptune’s count at once.
13. Psamathe
Image Source: Wikipedia
Psamathe is one of Neptune’s outermost moons and orbits in a retrograde direction. It was discovered in 2003 and sits at an enormous distance from Neptune.
A single orbit takes roughly 25 years to complete. Psamathe is very small and extremely faint, which made it hard to detect. It is thought to be a captured Kuiper Belt object.
Named after a sea goddess in Greek mythology, Psamathe is one of the least studied moons in Neptune’s entire family.
14. Neso
Image Source: Wikipedia
Neso holds a special place in the record books. It is the farthest known moon from its parent planet in the entire solar system.
Discovered in 2002, Neso orbits Neptune at such a massive distance that one orbit takes roughly 26 years to complete. It moves in a retrograde direction and is believed to be a captured object from the outer solar system.
Despite this record-breaking distance, very little is known about Neso’s surface, size, or exact composition.
15. S/2002 N5
Image Source: Wikipedia
S/2002 N5 is one of two provisionally designated moons of Neptune. It was observed in 2002 but has not yet received an official name.
Like many of Neptune’s outer moons, it follows a distant and irregular orbit. Its confirmation took years of careful observation.
Scientists continue to track it to better understand its orbital path. Once enough data is collected and its orbit is fully confirmed, it will likely receive an official name following Neptune’s sea-deity naming tradition.
16. S/2021 N1
Image Source: Wikipedia
S/2021 N1 is the most recently observed of Neptune’s provisional moons. Spotted in 2021, it is still awaiting official confirmation and a permanent name.
Very little is publicly known about its physical characteristics. It orbits far from Neptune and is believed to be quite small. Its discovery reflects just how much modern telescope technology has advanced.
Even a planet as distant as Neptune continues to reveal new objects, reminding everyone that the outer solar system still has plenty left to show.
Comparison: Neptune’s Moons vs Other Planets
Neptune has a decent number of moons, but how does it stack up against its neighbors?
| Planet | Number of Moons | Largest Moon | First Moon Discovered |
|---|---|---|---|
| Mercury | 0 | — | — |
| Venus | 0 | — | — |
| Earth | 1 | Moon | 1610 (Galileo) |
| Mars | 2 | Phobos | 1877 |
| Jupiter | 95 | Ganymede | 1610 |
| Saturn | 146 | Titan | 1655 |
| Uranus | 28 | Titania | 1787 |
| Neptune | 16 | Triton | 1846 |
Unique Facts About Neptune’s Moons
Neptune’s moons are full of surprises. These are some facts that make them genuinely stand out.
- Triton is the only large moon in the solar system that orbits its planet in the opposite direction to the planet’s rotation.
- Neso holds the record for the farthest known moon from its parent planet in the entire solar system, taking 26 years to complete one orbit.
- Triton has active geysers that shoot nitrogen gas several miles into the sky, making it one of the few geologically active moons known to science.
- Hippocamp, Neptune’s smallest inner moon, is believed to have broken off from Proteus following an ancient asteroid impact.
- Naiad orbits so close to Neptune that it completes a full trip around the planet in under eight hours.
- Triton is slowly spiraling inward toward Neptune and is expected to break apart into a ring system in roughly 3.6 billion years.
- Neptune’s outer moons are mostly thought to be captured Kuiper Belt objects, rather than moons that formed alongside the planet itself.
The Bottom Line
Neptune’s moons are far more interesting than most people give them credit for.
From Triton’s backwards orbit and nitrogen geysers to tiny Hippocamp barely holding itself together, each moon adds something worth knowing to the bigger picture of our solar system.
And with two moons still awaiting official names, the story is not yet complete.
For anyone curious about space, Neptune’s family of moons is a good reminder that the outer solar system still has a lot left to offer. Got a favorite moon from the list? Drop it in the comments below.
