Three ways to name a planet
With a meaning builds each name from a Latin or Greek word that suits the world you pick: glacies ("ice") for an ice world, pyr ("fire") for a lava world, anemos ("wind") for a gas giant. The card shows the word and what it means, so you can pick a name for its sense as well as its sound. Choose Any world for the whole mix, including words for light, stars and dawn.
Catalog style writes names the way astronomers designate exoplanets: a star's catalog name followed by a lowercase letter, as in TOI-1452 b. Pick a survey to keep one format, and tick Two stars for planets in a binary system, written like 16 Cygni Bb or Kepler-16 (AB)b. Each card explains what the prefix and the letter mean. These are made-up designations in a real format, so one can match a real planet by chance.
Made up strings together pronounceable syllables, Soft or Sharp, and shows how to say the name. These names mean nothing in any language we know of, which suits a world nobody has named yet.
Every proper name is checked against two of the IAU's rules for exoplanet names, 16 characters or fewer and preferably one word, and against names already taken: the solar system's planets and moons in this simulator, and the IAU's 2015 names for exoplanets.
Fly these names in the gravity simulator opens the gravity simulator with your first name as a Sun-like star and the next three as planets on circular orbits at 0.7, 1.3 and 2.4 AU. The scene opens paused; press Play to watch them go round, or add more bodies.
How real planets get their names
The solar system
Mercury, Venus, Mars, Jupiter and Saturn carry their Roman names because the early astronomers in Europe wrote in Latin. Uranus and Neptune were never seen by the Greeks or Romans, but they were given mythological names to fit the existing theme. Earth is the exception: its name is a Germanic word, about 1,000 years old, that simply means "the ground".
The planets' names were already in common use when the International Astronomical Union (IAU) formed in 1919. Today the IAU approves names for new bodies:
- Dwarf planets. The discovery team suggests a name to two IAU groups.
- Minor planets. Proposed names go to the IAU's Working Group for Small Body Nomenclature.
- Objects beyond Neptune. These get mythological names associated with creation.
Exoplanets: a catalog name and a letter
An exoplanet's scientific designation is its star's name, often a catalog entry, followed by a lowercase letter. The letter gives the order of discovery: the first planet found around a star is b, the second c, the third d. Planets found at the same time are lettered outward from the star. So c is not always farther out than b: it was found later.
| Prefix | What it means |
|---|---|
| HD | The Henry Draper Catalogue. The number is the star's place in that catalog, which was ordered by position. |
| GJ | The Gliese–Jahreiss catalog of stars near the Sun, within 25 parsecs. |
| TOI | TESS Object of Interest: a star NASA's TESS survey flagged for a possible planet. |
| Kepler | Stars whose planets NASA's Kepler mission confirmed or validated. |
| WASP | The Wide Angle Search for Planets, a survey with telescopes on La Palma and in South Africa. |
Stars in a system with more than one star take capital letters. A planet around the second star of a binary is written Bb, as in 16 Cygni Bb. A planet around both stars follows a scheme proposed in 2010: Kepler-16 (AB)b, or simply Kepler-16b when there is no doubt.
Official names for exoplanets
Some exoplanets also have proper names, chosen in public competitions the IAU runs, called NameExoWorlds. 51 Pegasi b, a giant planet found in 1995, is now Dimidium, Latin for "half", and its star is Helvetios. These are some of the names approved in 2015:
| Planet | IAU name | Origin |
|---|---|---|
| 51 Pegasi b | Dimidium | Latin for "half" |
| Epsilon Eridani b | Ægir | the Norse god of the sea |
| 55 Cancri b, c, d, e, f | Galileo, Brahe, Lipperhey, Janssen, Harriot | early astronomers and lens makers |
| 14 Andromedae b | Spe | Latin for "hope" |
| 18 Delphini b | Arion | an ancient Greek poet |
| Fomalhaut b | Dagon | a Levantine god |
The IAU's rules for these names are the ones this generator checks where it can:
- 16 characters or fewer, preferably one word, and pronounceable in some language.
- Not offensive, and not too similar to an existing name.
- No pets' names, commercial names, names of living people, or names tied to political, military or religious activity.
- Not the same as the planet's star.
Sources
IAU: Naming of exoplanets · IAU: Naming of astronomical objects · NASA: How do exoplanets get their names? (April 28, 2025) · NASA: How do planets get their names? (July 26, 2023) · NASA: Earth facts · NASA Exoplanet Archive: TESS Objects of Interest, Kepler names and GJ stars · Hessman et al. (2010) on naming planets in multiple star systems. Latin and Greek words as in Lewis & Short and Liddell–Scott–Jones on the Perseus Digital Library. Read October 6, 2026.
Questions
How do real exoplanets get their names?
Every exoplanet has a scientific designation: its star's catalog name and a lowercase letter. The first planet found around a star is b, the next c, and so on. A few also have proper names chosen through the IAU's NameExoWorlds competitions, such as Dimidium for 51 Pegasi b.
What does the b in an exoplanet's name mean?
It marks the first planet found around that star. The next one found is c, then d, and so on. Stars take capital letters (A, B) when a system has more than one.
Can I use these names in a story or game?
Yes. The names are made in your browser and are not saved or sent anywhere. Check that a name is not already used for a real object if that matters to you: the generator flags names it knows are taken.
What rules does the IAU set for planet names?
For exoplanet proper names, the IAU asks for 16 characters or fewer, preferably one word, pronounceable in some language, not offensive and not too similar to an existing name. Names of pets, commercial names, names of living people and names tied to political, military or religious activity are excluded.