In real life, constellations don't actually exist as discrete groupings of stars — what we perceive as constellations are simply casual patterns created by our perception of the night sky as a two-dimensional surface, and the individual stars within them are usually very far away from one another. Furthermore, because their shape is specifically the product of where their stars are located compared to Earth, they also only exist from a point of view in the solar system— extrasolar worlds would have alien night skies with entirely different constellations. note However, it's a common astronomy error in science fiction to treat constellations as though they were clusters of stars that are actually physically near each other, and to treat these as major astronomical areas and reference points. Often, this results in characters or cultures being described as being "from the so-and-so constellation", and in constellations being used to describe where a specific location is within the broader universe.
This trope typically uses real-life constellations, as part of the assumption that constellations are universal constants. However, some works may invent Fictional Constellations that will be used in the same manner. Such uses are arguably more justified— while the stars in real constellations are not clustered close together, there is no reason why a fictional constellation might not be so. Alternately, the meaning of the word "constellation" may have shifted in-universe to refer to stars that are actually in the same region, as interstellar travel made it necessary to have some convenient way to refer to such things.
Worth noting that this does happen with (some of) the stars in certain constellations, such as Ursa Major, Orion, or Scorpius, that share a common origin and are relatively close to each other. However, even in this case, these stars are often hundreds of light-years from each other.
Subtrope of Artistic License – Space.
Examples:
- The Five Star Stories is set in a group of star systems that are physically near each other, which many characters refer to as a constellation.
- Supergirl storyline "The Super-Steed of Steel": When the sorcerer Maldor and his evil master conspire to exile Biron to Sagittarius, they talk like that constellation was a specific place instead of an imaginary pattern on the sky.
- The Mind's Eye (1990): In the first segment "Creation", the camera flies through Orion's belt. Orion is shown to have all its stars exist on the same 2D plane.
- Blade Runner: During his famous speech at the climax, Roy Batty mentions having seen attack ships on fire "off the shoulder of Orion".
- The Fifth Element: The cruise ship is stated to be orbiting the planet Phloston in the "Angel" constellation.
- Men in Black: Discussed, lampshaded and ultimately subverted. A dying alien tells the heroes that "the Galaxy is on Orion's Belt", which they first take to refer to the strip of stars forming the "belt" of the Orion constellation. However, they are quickly refuted when they are shown that the "belt" in reality consists of only three stars (not enough for a galaxy) millions of light-years apart that only look like they are close together from Earth, and that there are no suitable galaxies in that particular direction of the sky. The alien's words turn out to refer to his pet cat, also named Orion, who carries a tiny galaxy hidden on his collar.
- Space Mutiny: Constellations are repeatedly referred to as meaningful divisions of space.
- Stargate: Played With. The titular gate uses constellations as reference points for a three-dimensional coordinate system (six constellations, one for each side of a cube, plus one non-constellation symbol for the starting point). The gate on Abydos has completely different constellations though, and Daniel has to find the coordinates for Earth for the expedition to go home. Stargate SG-1 and subsequent TV series quickly discard the "unique constellations" aspect and treat the symbols on the gates as a simple entry code for different planets, with extragalactic travel using seven constellation symbols and a point of origin (and extra power).
- Bio of a Space Tyrant: When Earth nations begin to colonize the galaxy after discovering faster-than-light travel, they divide their claims by each getting exclusive rights to a specific constellations. The United States get the Eagle, Russia gets the Bear, and China gets the Dragon.
- In Jack Vance's pentalogy The Demon Princes one character notes that "Ophiuchus isn't a star. It's a sector". There's also a reference to the Aquarius Sector.
- The Stainless Steel Rat: A planet is described as being "Second planet of a B star in Corona Borealis", but the setting is a sprawling interstellar civilization in which Earth (and the whole Solar System) is either unimportant, or even (in later books in the series) destroyed and its location no longer known.
- Stanisław Lem: In both The Invincible and Fiasco, the protagonists' spaceships arrive at constellations.
- The Zodiac Series: The twelve Houses are all Zodiacal constellations, with several planets and moons in each one.
- Doctor Who:
- Throughout the classic series, "constellation" is used as a synonym for "galaxy". The Doctor admits to being from "outside the constellation" several times, and that Gallifrey is (or was) in the constellation of Kasterborous. This happens so often that a later Expanded Material book justifies it by claiming that it's a result of meaning changing due to interacting with other spacefaring species who measure sectors by specific groups of stars rather than the present meaning.
- "The Trial of a Time Lord" — the season 23 story arc — repeatedly refers to Earth's entire constellation being moved by advanced aliens, ravaging Earth in the process.
- Star Trek: The Original Series: Implied with the Orions (the Trope Namers for Green-Skinned Space Babe). Background information and later parts of the franchise established that the green-skinned aliens were from the planet Orion, which is located in the Orion Sector (which sector is presumably geocentrically named for the Earth constellation).
- 3rd Rock from the Sun: The aliens' homeworld is located in the border territory between the Cepheus and Draco constellations.
- BattleTech: Several of the major factions, such as the Lyran Commonwealth (later Lyran Alliance), Draconis Combine and Taurian Concordat, are named for constellations and rule over large regions of space containing at least some of the stars in said constellations as seen from Earth, but their fanciful names are generally understood to be little more than poetic license (as are the other parts of their names, in many cases).
- JumpStart Adventures 3rd Grade: Mystery Mountain: The observatory Mini-Game has you figuring out which constellation Polly sent her father's spaceship to.
- Katamari Damacy: Constellations are physical groupings of stars until they were all destroyed by the King of All Cosmos on a drunken bender, and your job is to build new ones to place back in the sky.
- Star Control II: All the stars in a constellation are close to each other, forming contiguous regions on the hyperspace map. Given a handwave in the manual, which explains that these constellations are not the same constellations visible from any given planet, but were created after hyperspace was mapped from the patterns on the map and were merely named after old earth constellations due to superficial resemblance.
- Il Était Une Fois... L'Espace: Cassiopeia is said to control the neighboring constellations of Cepheus, Draco, and Andromeda, and aliens are described as coming from constellations such as Auriga or Centaurus.
