Numbered Homeworld

""It is true what they say: Women are from Omicron Persei 7, men are from Omicron Persei 9...""

- Ndnd of the planet Omicron Persei 8, When Aliens Attack

In speculative fiction, inhabited planets will often lack a proper name, instead being designated by the name of the star they orbit and a number. It is almost never the case that the star is referred to by a catalogue number. Natural satellites will also often lack proper names and be identified as "the moon of planet X" or somesuch.

In Real Life, notable celestial objects, like the other planets of the solar system, their moons and certain stars easily visible from Earth have had proper names for about as long they have been known to exist (although admittedly some are much better known than others). A large number of lesser objects, such as asteroids and extrasolar planets are assigned catalogue numbers. When extrasolar planets were first discovered in 1995, the astronomical community used lowercase letters instead of numbers (e.g. 51 Pegasi b, 70 Virginis b). While it is reasonable that an interstellar civilisation surveying a star system would initially assign numbers to the planets along the lines of "XLL325-1" for the first planet of the star XLL325, it would be strange if they failed to come up with proper names for the star and planets (eg. "Baltimore" instead of "XLL325") if they decide to colonise the star system. Even sillier is when a planet inhabited by an alien species is given such a label and said inhabitants begin to use that designation themselves. It's sillier still if the species has always called their own planet by a catalogue number. After all, how many humans in reality or fiction ever refer to our little world as Sol III?

This trope is arguably justified when the catalogue number is used by The Empire to name planets occupied by another species. Starfish Aliens may call their planet Krzjdlwsk (which is, admittedly, pronounceable as "Kzhid(u)lvsk" in Polish), but stormtroopers trying to pronounce the name may be tempted just use the catalogue number. Plain old humans, however, would be more likely come up with a nickname for the planet, like "Krazy Dullwhisk." May sometimes be a case of Translation Convention.

Anime and Manga

 * In Magical Girl Lyrical Nanoha Earth is also "Unadministrated Planet #97" to the Time-Space Administration Bureau. The Bureau categorizes the known worlds into administrated, non-administrated, and uninhabited, and numbers them (possibly) by the time of discovery. Mid-Childa, its homeworld, is "administrated world #1", for instance.
 * Outlaw Star uses this a lot, first with Sentinel III, and later with planets in the Heifong system.
 * Non-spatial example: Japan is renamed Area 11 in Code Geass.
 * This is chiefly a political move by Britannia, as it removes the identity of the conquered country to make it harder to establish a cause to revolt by.
 * Early in the series there's a reference to part of the former Middle East (Saudi Arabia) being referred to as Area 38. Presumably these numbers designate actual places under rule by the Brittanians.
 * In the Gundam series, especially but not exclusively in the Universal Century timeline, The Earth Federation names its artificial space colonies as "Sides", with the numerical designation of "Side x". For example, Amuro Ray's home was designated as "Side 7".

Fanfiction

 * In Aeon Natum Engel Earth is classified as Ƕǡ ѬѮӜ-[(zero-46,656) and (thirtyone-1296) and (eleven-36) and (thirtyfive)]-[(zero-60,466,176) and (one-1,679,616) and (twentynine-46,656) and (seven-1296) and (seventeen-36) and (three)]. Would be considered as a case of Exaggeration if not for beings who are using that numbering system, the Migou.

Film

 * Used occasionally in Star Wars: Yavin 4 is actually the fourth moon of the planet Yavin, there is also Hoth VI, Aduba-3, Telos IV, Malachor V and so on. However, the vast majority of planets where people actually live (Yavin 4 was just a base, for example) have a proper name, like Naboo, Coruscant, Tatooine and Kamino, although one (possible) exception is "(the Forest Moon of) Endor" where the Ewoks live.
 * The Chronicles of Riddick have Helion Prime and then up to Helion Five. The planet in Pitch Black is called M6-117.
 * Star Trek II the Wrath of Khan's main plot begins when someone mixes up the planets Ceti Alpha VI and Ceti Alpha V (one of them blew up and the other's orbit was shifted and became a desert wasteland as a result). Whoever forgot to COUNT THE FREAKING NUMBER OF PLANETS when they arrived in the system deserves to have some sort of parasitic worm shoved in their ear...
 * In real life, however, Pluto is not always the farthest (dwarf) planet, so when it happens, it's easy to confuse it with Neptune if one doesn't know their masses etc., but only counts objects.
 * Also in real life, it would be hard to live on a planet with an orbit so eccentric that it crossed that of another planet, at least when they're close to the sun
 * The planet where Aliens takes place on is called LV-426.

Literature

 * Not uncommon in The Hitchhiker's Guide to the Galaxy, sometimes using Greek or Roman letters instead of numbers, for variety. Several planets did have actual names, however: Earth ("What a boring name..."), Magrathea, Golgafrincham, Persephone Rupert...
 * In Lois McMaster Bujold's Vorkosigan Saga novels:
 * The Cetagandan Empire does this with Greek letters. There are eight planets and they're all "Something Ceta" - Eta Ceta, Rho Ceta, Mu Ceta and so on.
 * Cordelia Vorkosgian's homeworld of Beta Colony is technically a numbered homeworld, though Alpha Colony and Gamma Colony have since disappeared. As the name implies, it's very close to Earth in normal space (rather less so via the wormhole network, compared to other planets).
 * The planet Kibou-daini means "Hope #2", number sign and all — it's a very formal and technical form in Japanese and isn't usually seen out of signs and manuals. This is because there are multiple worlds called "New Hope" or the equivalent, and the two is required to distinguish it from the others.
 * In the Dune series of novels, the homeworld of the Ixians is called Ix, a mysterious name with a meaning lost to time. One character with "ancestral memories" notes to himself with amusement that "Ix" is merely the name of a numeral from a culture that has long been forgotten by the general population of the present universe. Seemingly implicit is that the planet was originally designated with the number 9, written in Roman Numerals as IX.
 * Several other plants have numbers, such as Wallach IX and IV Anbus (pronounced as "four-anbus").
 * LV-426, the setting for Aliens is named Acheron in the novelisation.
 * Although called Darkover by the natives, the official name of the planet is Cottman IV.
 * In Harry Turtledove's Worldwar series, The Race's homeworld is named Home, and the other two planets under their rule are follow the [Star][number] convention - Halless 1 and Rabotev 2. They call their latest target Tosev 3, the third planet from the star Tosev. The Tosevite locals call it Earth.
 * Asteroid B612, home to The Little Prince.
 * Possibly justified in Stephen Baxter's Manifold Space. The Gaijin refer to their homeworld as Zero-zero-zero-zero, indicating it's their "point of origin," but the Gaijin are Mechanical Lifeforms who don't have a human-like mode of consciousness.
 * The Perry Rhodan universe has the Arkonides calling their homeworlds Arkon I, II and III. This is quite intentional, since they were moved into an equilateral triangle with the star in its center (they were originally the 2nd to 4th planet). The other planets in the system have names.
 * In The History of the Galaxy series, many secret Earth Alliance automated bases throughout the galaxy are called "Omicron"+ . This is likely to hide their locations from enemy spies.
 * In one of the Lensman novels, Tregonsee comments in passing that he thinks of his homeworld as Rigel IV, and only bothers with a more accurate designation if he needs to give astrogation coordinates. This implies that the Rigellians don't have an independent name for their homeworld (but could simply be Lens-related Translation Convention).
 * In Sergey Lukyanenko's Rough Draft and Final Draft, all parallel worlds have a numerical designation, the origin of which is not known. Our world is Earth 2. Many of the mentioned worlds have proper names, although the numerical designation is used most often. For example, our world is sometimes called Demos, due to the prevalence of democracy. It was initially assumed that there are only about two dozen parallel worlds. However, the number is later revealed to be at least double that (possibly, infinite) with Earth 46.
 * Almost entirely averted in Ursula K. Le Guin's Hainish novels. The exception is Eleven-Soro, which features in only one short story, "Solitude".
 * The Star Wars Expanded Universe generally does this quite realistically--the only planets with numbers are those home to small or recently founded colonies, such as Comkin Five.
 * In one of the Soul Drinkers novels, an Adeptus Mechanicus world is referred to solely by a "serial number"-type name. Of course, given the nature of that particular branch of the Imperial hierarchy, that's about par for the course.

Live Action TV
"Londo: We thought your world was Beta 9, actually it was Beta 12"
 * Star Trek:
 * Star Trek the Original Series. Just a few of the many examples:
 * The planets in the Rigel system: various episodes mention 2, 4, 7 and 12.
 * The Sigma Draconis system ("Spock's Brain") has nine planets and mentions numbers 3, 4, 6 and 7.
 * Aldebaran III in "The Deadly Years."
 * Alpha Carinae II ("The Ultimate Computer") and V ("Wolf in the Fold").
 * At least some of these can be Handwaved by the fact that the natives (if there are any) may have their own names for said planets. Others... not so much.
 * Star Trek the Next Generation had the episode "First Contact" (not to be confused with the movie), featuring a previously uncontacted race who believed that they were a higher species and their planet was the center of the universe, but they called it by the Federation name of Malcor III (Justified by the near-Omnipotent universal translator).
 * The Cardassian homeworld is called "Cardassia Prime." Other planets in the Cardassian system are numbered. Planets in the Bajoran system also have numbers, but the homeworld itself is simply "Bajor."
 * Most or all planets in Stargate SG-1 were numbered, although many had proper names as well. Earth has one as well: P2X-3YZ
 * They were generally pretty good about this trope, though. When they encountered an inhabited planet, they usually switched from the catalogue number to whatever the natives call it. Of course, the characters did manage to remember offhand the catalogue numbers for many of their mission destinations even years later.
 * Carter mentions in one episode that the designation is "based on a binary code the computer uses for extrapolation," so it's some kind of a mathematical formula produced by the Earth-based dialing computer to pinpoint location in space. It would seem that the first digit may indicate galaxy, since every Milky Way address seems to begin with "P," while every Pegasus address seems to begin with "M" (in spite of common sense suggesting it should be the other way around).
 * The "P" in all probability comes from "planet"; "M" might've been chosen with the intent to have most of the Pegasus worlds be moons. The P = planet, M = moon is likely exemplified by M4C-862, which is in the Milky Way, but referred to many times as a moon.
 * Lampshaded in a first-season episode of Atlantis, where after having to be reminded what planet a particular code corresponded to, Ford asked why they couldn't simply give descriptive names to the planets like "Planet Waterfall".
 * Power Rangers in Space: Andros's homeworld is "KO-35" and referred to as a colony. It's in the "Kerovan system." That... doesn't actually give a proper name to Andros' people or their world. Fans speculate that the planet it's a colony of (which is, by the way, only suggested to exist by Fridge Logic - for KO-35 to be "the space colony" there must be an original civilization... and that's all we got.) must have a proper name.
 * Used to some degree in Babylon 5: It's mostly only colony worlds that retain numbered designations (the human Deneb IV, or the disputed Centauri colony at Ragesh 3). The only exception is the name of Centauri Prime, but it's possible that this is a back-designation and there's a "New Centauri" somewhere in the Centauri Republic.
 * The Centauri also claimed that Earth was a Lost Colony due to "clerical error:"


 * From Lexx, a literal numbered homeworld: Brunnis-2 is where all the inhabitants of Brunnis settled after abandoning their original star system (and universe).
 * Also spoofed with the unreachable Pleasure Planet "Nimbus IX."
 * Stan is from Ostral-B which seems to be similar to this, and Zev/Xev was from "B3K".
 * In Doctor Who Earth has occasionally (such as in "Last of the Time Lords") been identified as "Sol 3" from outside sources.
 * There was a Saturday morning show, Far Out Space Nuts, about two accidental astronauts. At the end of one episode, the aliens they'd just helped offered them a ride to "Sol 3," where the aliens planned to vacation -- but our heroes declined, because they needed to work on returning to Earth. Oops...

Tabletop Games

 * Warhammer 40000 uses names like Lorne V and Kaurava IV on top of more standard titles. But the also tend to name a star system after its most important planet, a subsector after its most important system...

Video Games

 * Tallon IV from the Metroid games. Actually sort of confusing in Metroid Prime. There's a room that gives you a holographic display of the solar system. Tallon IV is actually the fifth planet in that system and the system itself is called the Ooromine System. There is an Ooromine II, but the other planets have distinctive names. This includes Zebes (the planet of the original Metroid and Super Metroid), Billium and Twin Tabula.
 * The Metroid home planet is SR388. Justified as the name is a catalog name given by the Federation. The planet was never colonised by them (due to certain nasty energy-sucking jellyfish-things) and so there's no reason for a proper name. Samus' own home colony is K2-L.
 * The second Alien vs. Predator game takes place upon LV-1201.
 * In EVE Online, every planet and moon is numbered. Only planets in the homeworld systems of Amarr, New Caldari, Luminaire, and Pator, get proper names.
 * Furthermore, the systems not controlled by the NPC empires all have numeric designations like B-VIP 9. There have been proposals to name some of these systems after characters whose players died in real life.
 * This trope exists in the Halo universe with the planets Chi Ceti 4, Eridanus II, Charybdis IX, and Sigma Octanus IV. There are also a few numbered planets that aren't named after the star they orbit; Draco III, Paris IV, and Jericho VII. Jericho VII is especially odd, the UNSC colony Arcadia is within the Jericho system while the Jericho VII itself is in the Lambda Serpentis system.
 * In the 4X game Galactic Civilizations II the homeworlds of the various species and the other planets in the same system have proper names. Other systems with no native intelligent species however have planets with Star Name + Number. The player is free to rename them though when colonized.
 * Minor races have their planets named after them. Some, like the Dark Yor, even have their own solar system (following the standard naming convention for the various planets).
 * The campaign maps usually have a few planets with unique names.
 * The Star Ocean series uses both this and proper names for planets. For example Earth is also known as Sol III while Expel is also known as Arcura IV.
 * The second and third Master of Orion games all have numbered planets. You can name the star though, so you can settle on Trope IV.
 * In Xenosaga all of the capitals of Galaxy Federation have been named _th Jerusalem, with Earth being named Lost Jerusalem, and the capital during the game's events Fifth Jerusalem.
 * By default, Outpost names the planets in this way while using the names of real stars, resulting in planet names like "Sigma Draconis I" or "Delta Pavonis II." You can, however, rename the planet to your liking, and Outpost 2 simply calls the planet "New Terra."
 * Averted in Mass Effect. Most planets and solar systems that you visit in the game have already been explored by someone, and as such already have names associated with them. Even lifeless rocks in distant nebulae have names. Some come from human mythology and history, but most have been named by the various alien races that have already been established in the galaxy for millennia. The only exceptions are 2175 Aeia and 2175 AR 2, never formally explored and thus never given a name beyond the scientific designation.
 * In Star Trek: Birth Of The Federation, nearly all planets follow the trope. Earth and the Solar System planets are the exception. Interestingly, the first planet in a system is always called + "Prime". The rest attach Roman numerals. Cardassia Prime is the exception, as it is normally the second planet in the system, and the first planet is named Cardassia II.
 * In Spore, catalogue numbers are reserved for anomalies like black holes; every star or binary system has a name. Planets, however, including homeworlds, are designated using the name of the star or binary system followed by a number, except for the player homeworlds, which are named when you first start a game on that world.
 * Freelancer gives the sparsely populated Border Worlds names like "Sigma-14" and "Tau-23," while those under house authority are named after places on Earth, such as "New London" or "Frankfurt."
 * It doesn't matter if it's your homeworld. In Space Empires it'll still be called "Wolf 359 VIII".
 * In Star Control II, planets are referred to as the name of the star plus a number (such as Eta Vulpecolae I). Aliens do have names for their homeworlds (e.g. Spathiwa, Fahz, Vlik, Falayalaralfali), but they will often use the standard name in conversation, presumably because it makes them easier to find.

Webcomics

 * In the Zap! webcomic, "Stickles" (an alien race) come from Stickbat 7. The number isn't because it is the seventh planet from the star, but because they've accidentally destroyed six other homeworlds in crazy experiments. As one stickle said, "[the other planets] were too flammable."
 * In the Punyverse from Sluggy Freelance this seems to be standard practice, with planets named things like Grittania-3 or Chau-5.
 * Parodied in Starslip when Vanderbeam visits the planet Oculus IV, which inhabited by a race of blind aliens. Once Vanderbeam comments on the "irony", his host replies that there is none since only humans call the planet Oculus IV (they call it "J'tlz'kr") and that he's tired of every single human visitor bringing up the same observation.

Western Animation
"Infosphere Brain: "Clarification request. Are you the Philip J. Fry from Earth, or the Philip J. Fry from Hovering Squid World 97A?" Brainspawn: "Earth, you fat idiot.""
 * Hanna-Barbera's Galaxy Trio did this a lot.
 * Kang and Kodos from The Simpsons Halloween Episodes come from the faraway planet of Rigel VII (also called Rigel IV in some earlier episodes).
 * The Planet X is homaged in the animated sci-fi spoof Duck Dodgers in the 24½th Century and the Captain Proton holoprogram (based on Flash Gordon-type sci-fi) in Star Trek Voyager.
 * As quoted above, in Futurama the Omicronians call their home planet "Omicron Persei VIII." This is a "Numbered" Star as well as a numbered homeworld. Omicron Persei just means the 15th brightest star in the constellation Perseus as seen from Earth, and it's a real star.
 * And when finding out what life would be like if it were a video game, it turns out the Space Invaders were from the planet Nintendu LXIV.
 * In fact almost every planet in Futurama is named this way. Amphibios IX, Decapod X, Chapek IX, Dogdoo VII, Tweenis XII. there are few exceptions.
 * Further lampooned and played completely straight during the second second Brain Spawn episode.

Real Life

 * It has been pointed out that if a real person/alien came forward and claimed to be from a planet around a star with a recognizable name like "Arcturus" or "Vega" the claim could easily be considered to be false right off the bat. It's not that they're using our name while speaking our language. (When was the last time somebody told you, in English, that they're from 'Deutschland' or 'Nippon?') It's that there are literally billions and billions of stars, and the chances of an alien just happening to be from one of the only one hundred or so recognizable stars we even have names for is a pretty astronomically small chance. Bright stars are not only outnumbered by smaller, dimmer stars by a long shot (our own sun isn't particularly bright itself, being in the middle range), and just because a star is bright to us in the sky doesn't mean it's close to us, either.
 * Also, highly luminous stars burn out relatively quickly (a few tens or hundreds of millions of years rather than the ten-billion-year life of a star like Earth's sun), making them poor candidates for inhabited planets.
 * A variation of this: the first Earth-like exoplanet to be discovered within its star Goldilocks Zone is named Gliese 581 g, also known as Zarmina's World.
 * This is actually standard naming procedure for exoplanets in the IAU. Basically, each exoplanet discovered has been named (star name) + (lower case letter). The key difference from typical science fiction convention is that they use letters instead of numbers and that the letter corresponds to order of discovery, rather than distance from the star. For example, Gliese 581 g is not the sixth planet from its star (which we can't know for certain at this point anyway) but rather the sixth planet discovered in the system. It's actually the closest (we know of) to its star.
 * To carry this further, Jupiter would probably be Sol b to non-humans (assuming they used the same naming convention), since it would probably be the first planet to be discovered.
 * Though Earth is intriguingly bright in the microwave band.
 * Though Gliese 581g has since been discredited (someone probably fudged some data), the principle holds true.
 * Earth would be called "Sol-3" if we didn't live on it. Officially, we could also call it Sol b since it's the first planet we discovered.