Planet Name Generator

The planets of our own solar system are named for Roman gods — Mercury, Venus, Mars, Jupiter, Saturn, Neptune — with Uranus the odd one out, taking a Greek name instead. Earth is the true exception: it is the only planet not named after a deity, deriving instead from old Germanic words simply meaning the ground. Astronomical naming today is overseen by the International Astronomical Union, which sets the conventions for what may be named and how.

That mythological tradition is why classical roots still read as authentically planetary. A name built on Greek or Roman elements will sound like it belongs in an astronomy textbook, which is exactly the effect most science fiction wants.

Planets outside our solar system are named quite differently, and the system is worth borrowing. An exoplanet takes the name of its host star followed by a lowercase letter, assigned in order of discovery and beginning at b rather than a — so the first planet found around a star called Kepler-186 is Kepler-186b, the next c, and so on. This is why real exoplanet names look like catalogue entries rather than names.

For fiction this is enormously useful. A world referred to as a designation implies a universe with surveys, bureaucracies, and more planets than anyone has bothered to name properly. Mixing the two registers — a formal designation plus a colonists' nickname — instantly suggests a settled world with a history.

The most common weakness in invented planets is that every world in a setting sounds like it was named by the same person. In practice, worlds would be named by whoever found or settled them: a survey catalogue, a corporation, a colony ship's crew, an indigenous population, or a coloniser overwriting all of the above.

Vary the sources deliberately. A system containing one classical name, one bland catalogue designation, and one blunt settlers' name reads as a real region of space with a complicated history — and the contrast between them tells the reader who got there first.

Science fiction has developed its own shorthand. Appending Prime marks a system's principal or first-settled world; Roman numerals number planets outward from their star; and Minor, Major, or Secundus distinguish siblings. None of these are official astronomical conventions, but readers parse them instantly, which makes them efficient.

Use them sparingly and consistently. A setting where every planet has a Prime or a numeral starts to read as filler, but one well-placed designation does a lot of worldbuilding for very little effort.