How to name planets that sound truly cosmic
Sci-fi planet names follow three traditions. First: catalog code, like Kepler-186f, HD 209458 b, Trappist-1e. Works in hard sci-fi because it mimics real exoplanet nomenclature. If your universe has a centralized space agency, this code is coherent.
Second: mythological name, like Arrakis (Dune), Coruscant (Star Wars), Caprica (Battlestar Galactica). Borrows resonance from real mythologies (Greek, Sumerian, Latin) and gives narrative weight immediately. Works when planets are personified in the story.
Third: biome-descriptive name, like Hoth (ice world), Tatooine (desert world), Endor (forest moon). Obvious but effective in space opera where each planet has a single biome. Decide which tradition fits your tone before generating names. A hard sci-fi novel deserves catalog code, friendly space opera works with mythological names.
Patterns by genre and atmosphere of your universe
For hard sci-fi (Liu Cixin, Andy Weir, Kim Stanley Robinson), prioritize realism. Mix official designation with colloquial nickname: Kepler-22b formal, Aurora casual among colonists. This reflects how we name things in real life: NASA says 2014 MU69, humans say Arrokoth.
For space opera (Star Wars, Mass Effect, Foundation), allow more evocative names: Tarken Mira, Vexion-IV, Helverax. They can have mythological resonance without being literal. Star Wars uses a consistent grammar: two syllables, open sounds, soft endings (Naboo, Hoth, Yavin).
For cyberpunk in space (Altered Carbon, The Expanse), names with corporate flavor: Mars Sigma, Ceres Station, Lagrange-9. The everyday mixes with industrial. For cosmic horror sci-fi (Lovecraftian), unpronounceable names hinting at unintelligibility: Yiothth, K'arnax. Without overdoing it (one apostrophe max). For space RPG universes (Traveller, Stars Without Number), generate 30-60 names per system; players will invent their own emotional bond with the ones they visit.
Mistakes that break planetary immersion
The first mistake is imitating Earth names with minimal change. New Earth, Mars 2, Planet Argentina break suspension of disbelief. Your universe is vast and ancient; names should feel from there, not from 2024 Earth. Exception: if your narrative deliberately explores human colonial nostalgia (New Caprica in Battlestar Galactica works because humans flee).
The second mistake is inconsistent nomenclature across planets. If your universe has Vexion-IV, Coruscant and Bob, you mix three traditions that clash. Define which culture names which. Humans give Earth-mythological names; Krellians use numeric coding; Rrak'tor use unpronounceable names.
The third mistake is only pretty names without ecological function. A planet called Aurora that turns out to be a radioactive wasteland needs justification: who named it? Colonial irony? Ancient name pre-radiation? The inconsistency between name and biome must be narrativized. The fourth mistake is Hollywood-forced suffixes. Planet Glorgon Prime VII is parody. If you use numeric or Greek suffixes, do it with criteria: -Prime suggests system capital; VII suggests seventh planet in system; Beta suggests second naming.
How to build a complete solar system from the names
A well-built solar system has a host star with designation (Kepler-186, HD 40307) and planets orbiting it with derived names (Kepler-186b, HD 40307c) or independent names once colonized. Decide which phase your universe is in: discovery, exploration, settlement or mature civilization.
In discovery phase (a century after first contact), planets still have technical designations with emerging popular nicknames. Trappist-1e, known as Cradle. In settlement phase (a millennium later), the nickname displaced the code and new colonists adopt it as the official name.
In mature civilization phase (ten millennia later), planets have their own lore, names in multiple alien languages, local mythologies disputing the original name. Arrakis is also Dune, also Rakis depending on the era. This historical depth elevates your worldbuilding from amateur to professional. For space games like No Man's Sky or Stellaris, generate 100+ names and group them by biome type so the engine assigns them coherently. Advanced tip: include planets with forbidden or taboo names (genocides, catastrophes), where the mention itself carries narrative weight.