[[quoteright:320:[[Film/ANewHope http://static.tvtropes.org/pmwiki/pub/images/tattoine_2071.jpg]]]]
[-[[caption-width-right:320:Never, ever forget your sunscreen on Tatooine.]]-]

->''I cannot tell you what it meant to me to see the two suns of Ferro set behind the dry mountain east of my home.''
-->-- Opening line of '''A Dry, Quiet War''' by Tony Daniel

A trope where a planet has two suns in the sky, either orbiting one of them or travelling in a long orbit around both of the stars. Occurs primarly in sci-fi settings, but certainly isn't limited to it.

Their prevalence in science fiction is actually an example of RealityIsUnrealistic, because binary stars are in fact much more common than single stars like our Sun[[note]]At least, when dealing with stars comparable in size and intrinsic brightness to the sun (as well as with massive stars, that like to form part of double or multiple systems). The smaller, dimmer, and much more numerous red dwarf stars are usually solitary; solitary red dwarfs actually make up the majority of all star systems in any given significant volume of space.[[/note]], although it is uncertain how likely it is that habitable planets would form in the presence of two suns (for the sake of RuleOfCool, though, it's best [[MST3KMantra not to ask]]). So there is still some ArtisticLicenseAstronomy involved.

There are three realistic possibilities for this arrangement:
* Type I: "Twin Suns" -- The suns rise and fall with each other, indicating that the suns orbit each other closely and the planet orbits both of them.
* Type II: "Close Stars" -- The suns may occupy different parts of the sky, indicating that one sun orbits the other farther out than the planet.
** Subtype II a: "Bright And Dark Seasons" -- With low axial tilt or near the equator, at one point both suns will appear close in the sky, and it becomes night when both set. About half a planet year later, usually one sun will be in the sky, and there will hardly be a real night.
** Subtype II b: "Midnight Sun" -- With high axial tilt or near the poles, the outer sun may remain [[EndlessDaytime above]]/[[AlwaysNight below]] the horizon for many years.
* Type III: "1 1/2 Suns" -- The planet has one "Sun", with night and day according to it, but another star in the same system is identifiable as a small sun that contributes some heat and sometimes leaves night more like twilight. This indicates that the planet orbits a single star in a double-star system, and the stars orbit each other at a large enough distance for one or both to have its/their own separate habitable zone(s). This is by far the most likely arrangement in reality as far as habitable planets go.

There are also unrealistic and unstable configurations:
* Type IV: "Between Two Suns" -- The planet is positioned between two suns, providing for EndlessDaytime.
* Type V: "Figure 8" or similar -- The planet orbits one sun, then the other, in a regular way. If the suns of Type I are too far from each other, it may also become this.[[note]]Technically a figure-8 is called a "lemniscate of Bernoulli", and one thing wrong with this scenario is that this is an order-6 curve, not the order-2 curve a real stable orbit would be.[[/note]]

Type IV and V would realistically decay into:
* Type VI: "Chaotic Orbit" -- A planet in chaotic orbit might exist, but wouldn't be able to support life. Also, the chaotic orbit would eventually throw the planet into one of the suns, or out of the system.[[note]]''Brief'' figure 8 orbits are possible -- the free-return trajectories flown on the Apollo missions were figure 8s -- but these are never stable.[[/note]]

A SubTrope of AlienSky.


[[folder:Anime And Manga]]
* In the later part of ''Anime/{{Braiger}}'', and throughout its sequels ''Bikezinger'' & ''Sasuliger'', the Solar System becomes a binary star system after BigBad Carmen Khamen uses the J9 robots' [[TelescopingRobot size-changing]] "Synchron System" to increase Jupiter's mass to the point where it can sustain nuclear fusion.
* Planet Namek in ''Franchise/DragonBall'' has '''three''' suns, and perpetual daytime because at least one of them is always in the sky at any given time.
* The eponymous stars of ''Manga/TheFiveStarStories'' may or may not be a quintary star system, though the English translation inconsistently renders it as either [[SciFiWritersHaveNoSenseOfScale "star cluster", which usually have thousands of stars, or the patently absurd "galaxy"]]. At any rate they're far enough apart that you usually can't see them from each other's planets during daytime.
* While ''Anime/GaoGaiGar'' mainly takes place TwentyMinutesIntoTheFuture on good ol' Earth, [[spoiler: Mamoru and Kaidou]] actually hail from the green and red planets of a ''trinary'' solar system, and almost the entirety of the OVA series ''Anime/GaoGaiGar FINAL'' takes place there as well.
* In ''Manga/{{Trigun}}'', Gunsmoke is a [[DesertPunk desert world]] with twin suns.

[[folder:Collectible card games]]
* In ''TabletopGame/MagicTheGathering'', Mirrodin has five suns -- one for each color of mana. They orbit the planet instead of vice versa, but their gravitational effects on each other and Mirrodin would cause some different problems.
** Arguably justified in that they are [[spoiler:made of pure mana.]]
** Amonkhet has two suns: a "normal" sun that moves normally across the sky, and a second one that moves slowly. As such, its almost perpetually drenched in [[EndlessDaytime daylight]].

[[folder:Comic Books]]
* In the Marvel comics, ComicBook/TheTransformers homeworld of [[CityPlanet Cybertron]] is said to have orbited Alpha Centuari before being knocked out of its orbit, placing it in a binary star system, but said stars are never actually seen at once.
* ''ComicBook/{{Vampirella}}'': Satyr and Circe! (The twin suns of Drakulon; from their description and dim memory possibly BY Draconis.)

[[folder:Comic Strips]]
* Calvin in ''ComicStrip/CalvinAndHobbes'' once imagined Spaceman Spiff landing on a hostile alien planet "scorched by twin suns". He is then attacked by a monster (which turns out to be Calvin's mom).

* ''Franchise/StarWars'' has one of the best known examples, the iconic double-sunset Luke Skywalker contemplates on Tatooine in ''Film/ANewHope''. Also indirectly the TropeNamer; the soundtrack name is [[https://www.youtube.com/watch?v=LxDm-4Jrg9w Binary Sunset]].
** The planet Ahch-To from ''Film/TheLastJedi'' has a double-sunset as well. And Luke contemplates it again [[spoiler:as he dies and [[AscendToAHigherPlaneOfExistence becomes one with the Force]] after channelling an illusion on Crait to fool the First Order and help saving what's left of the Resistance, {{book end|s}}ing his life as a HopeBringer for the galaxy.]]
* ''Film/TwoThousandTenTheYearWeMakeContact'': After [[spoiler:Jupiter]] is turned into a sun.
* ''Film/TheDarkCrystal'' features three suns of differing sizes and colors, with the climax happening [[WhenThePlanetsAlign When The Suns Align]].
* In ''Film/GuardiansOfTheGalaxy'', the Xandarian system has triple-suns, which are symbolized in the Nova Corps emblem.
* In ''Film/PitchBlack'', the main planet has three suns, and has almost constant daytime. However, when nighttime does fall, there's serious trouble.

* A planet which quickly becomes significant in the ''Cadre'' trilogy has ''three suns'' with visibly differing masses and ages, as well as a ''black hole'' close enough to be usually visible in the daytime sky. The sheer uniqueness of this arrangement, coupled with the fact that the first colonists lost navigational control and spent over a month helpless before gravitational forces neatly brought them to the planet led to the foundation of a system of religious philosophy which dominates the latter two books.
* Creator/ArthurCClarke's ''Literature/ChildhoodsEnd'' briefly visits a planet that orbits ''eight'' stars. This gives it an utterly bizarre orbit in which every moment brings a unique arrangement of planet and stars.
* The homeworld of the utods in ''The Dark Light Years'' is in a trinary star system, and has a very peculiar orbit: periodically, the combined gravities of the two other suns pull the planet away from its current sun, moving it to circle a different one.
* Darwin IV, the planet described in Creator/WayneBarlowe's ''Literature/{{Expedition}}'', has twin suns. The term "sunslight" is used several times in the text, the better to remind readers of this.
* The ''Literature/{{Helliconia}}'' trilogy is set in a binary system, with the eponymous planet orbiting a dim sun called Batalix, and both Helliconia and Batalix orbiting a larger blue giant star called Freyr in a slow, highly elliptical orbit. This gives Helliconia centuries-long seasons, with powerful consequences for the development of its human civilization.
* Arthur Dent is impressed by watching a twin sunset from Magrathea in ''Literature/TheHitchhikersGuideToTheGalaxy1''. Marvin is a little more jaded.
* Literature/HonorHarrington 'verse:
** Technically the Manticore system, with Manticore and Sphinx orbiting Manticore-A while Gryphon orbits Manticore-B. However they are what's called a distant binary with enough separation that Manticore-B would just be a very bright star in the night skies of Manticore and Sphinx.
** A similar situation (with only one habitable planet per sun) in the Nuncio system in the Talbott Cluster. These may actually be more realistic since current models suggest that telluric (rocky) planets can't form stable orbits in a binary system where the two stars are close enough to form a traditional two suns situation
** Literature/HonorHarrington has a '''lot''' of binary star systems. Since it's not a visual medium, and there are rarely habitable planets orbiting both stars, it doesn't really matter much, though.
* Creator/IsaacAsimov's "Literature/{{Nightfall}}" takes place on a world with ''six'' suns. The novel focuses on the effects that a long period of darkness would have on a species accustomed to unending day.
** [[spoiler:For the first thirty seconds, people panic because the lights went out. For a few minutes after that, they all gaze at the stars, because they've never seen stars before. And then, all of them go insane (to varying degrees) from realizing how insignificant they are in the universe. Society collapses overnight.]]
** Asimov later realized such a system is unlikely to be stable, so he wrote ''Sucker Bait'' -- only two suns, ''but this time, I'm getting it right''.
* Norfolk in Peter F. Hamilton's ''Literature/NightsDawnTrilogy'' orbits the primary star of a binary system, lending a unique system involving "Duke day" (full white sunlight from the primary, Duke), "Duchess night" (red sunlight from the secondary, Duchess) and true night for the portions hidden from both stars. Duke day lasts for the same time all the time (at least at the equator), but Duchess night and true night pass between complete Duchess night and complete true night depending on the planet's position around its orbit.
* The planet Placet in Creator/FredricBrown's story "Placet is a Crazy Place" orbits two suns in a figure-of-eight. When it is between the suns, the human colonists experience visual hallucinations. This is only ''one'' of the reasons why it is considered crazy.
* ''Quest For The Fallen Star'' has the world in a figure-8 orbit, with another planet called Coldaria orbiting the whole system at a great distance.
* The Ranadon star system in Jennifer Fallon's ''Second Sons'' Trilogy concerns two suns, one a big red one seen at night, and the other a little yellow one during the day, as seen from the planet Ranadon. Every so often the red sun goes wandering, causing the 'Age of Shadows'.
* Creator/StanislawLem's ''Literature/{{Solaris}}'' has the eponymous planet of the kind described by the types IV to VI. The fact that its orbit is unrealistically stable is [[GeniusLoci a plot point]].
* ''Literature/StarCarrier'': The first book's Eta Boötis System consists of a large sun and a white dwarf, with the inhabited planet Haris orbiting about twice as far out as the dwarf. This is suspected as a possibility for the real life Eta Boötis, but not currently confirmed.
* The planet Naxera in Literature/StarTrekTheLostEra. The two suns are named for mythological brothers -- G'Dok and Leahru -- who also give their names to the two largest Naxeran [[FantasticCasteSystem castes]].
* Binary stars become a plot point in ''Literature/TheLostFleet'' series. The [[HyperspaceLanes jump points]] around them are unstable meaning that while you can use a jump drive to leave a binary system it's functionally impossible to use them to reach a binary system. However, it is possible to use sub-light travel to get to a binary system and then build a [[PortalNetwork hypernet gate]] (the second form of FTL travel in the series) in order to allow travel to and from the system.
* The planet on which Melissa Scott and Lisa A. Barnett's Astreiant novels take place orbits the larger star of a binary system. The inhabitants call the smaller star the Winter-Sun.

[[folder:Live Action TV]]
* ''Series/{{Angel}}'': The two suns in Pylea.
* While it's never specified if the Votan system in ''Series/{{Defiance}}'' had two stars before the stellar collision, one of the songs on the soundtrack mentions "twin suns".
* ''Series/DoctorWho'':
** The Doctor's homeworld Gallifrey is in a binary star system.
** [[Recap/DoctorWhoS30E6TheDoctorsDaughter "The Doctor's Daughter"]]: Messaline has three suns.
** As does San Helios from [[Recap/DoctorWhoS30E15PlanetOfTheDead "Planet of the Dead"]].
** The human colony world in [[Recap/DoctorWhoS36E2Smile "Smile"]] has two suns.
* In an episode of ''Series/SesameStreet'', Elmo read to María a story he wrote and illustrated about an imagined trip to a planet with two suns in its sky.
* On ''Series/{{Smallville}}", the Phantom Zone has two suns. When Lois is trapped in the phantom zone with Clark, this leads her to thinks she is not still in Kansas.
* ''Series/StargateSG1'' features three binary systems in the first five seasons alone. The Jaffa world Chulak is a heavily forested planet orbiting a binary. A later episode briefly has SG-1 trapped on a binary-orbiting desert world because the stargate overheated when the second sun rose, preventing them from dialing out.
** The Aschen have the ability to create ''artificial'' binary systems by inducing fusion in gas giants. Somehow, the resulting star system is actually stable, as evidenced by the planet Volia in "2001".
*** This is a ShoutOut to Arthur C. Clarke's novel ''[[Literature/TheSpaceOdysseySeries 2010: Odyssey Two]]'', wherein the same is done to Jupiter.
* A ''Series/StarTrekTheNextGeneration'' episode called "Night Terrors" is set in a binary system.
* Oz (excuse me, [[InsistentTerminology "the Outer Zone"]]) in ''Series/TinMan'' has dual suns and several moons. The plot concerns an [[TotalEclipseOfThePlot upcoming double eclipse]] in which both suns are behind one of the moons at once.
* ''Series/TheTomorrowPeople'' briefly mentioned a planet called [=QX5=] that orbited two suns.
* The ''Series/TwilightZone'' episode "On Thursday We Leave for Home" concerned a group of colonists marooned on a distant planet, barely able to eke out survival thanks in part to the binary sun and endless brutal daytime.

[[folder:Tabletop Games]]
* R. Talsorian's ''TabletopGame/{{Mekton}}'' game line uses a default setting of the Algol star system, correctly identified and diagrammed as a quaternary system, the fours stars being Algol, Kobol, Minbar, and the Dark Companion. The "dark" companion is a G0 yellow dwarf, just like Sol.
* The Tau Empire sept world of Vior'la in ''TabletopGame/{{Warhammer 40000}}'' orbits a binary star. Its orbit causes it to pass between the two stars every year, close enough for the planet's surface to be ravaged by intense plasma storms, with the Tau living in specialized Hab-domes during this season. It's also well known for producing some of the toughest and elite members of the Fire Warrior Caste, so it should come as little surprise that the name Vior'la is Tau for "HotBlooded".

* In Metru Nui, of the Toys/{{Bionicle}} franchise, there are two suns. [[spoiler: They're actually the eyes of the robot Mata Nui, and Metru Nui is his brain. The matoran are maintenance systems, comparable in size to cells in the human body. When the suns "go out" is when Makuta put Mata Nui "to sleep".]]

[[folder:Video Games]]
* Due to its cross-over reference on the famous TropeCodifier, ''VideoGame/AngryBirds Franchise/StarWars'' features Tatooine and its two suns (though it shows them as a big red star and a smaller yellow one.)
* Irdya, the world of ''Videogame/TheBattleForWesnoth'', originally has only one sun, but another is raised to banish the darkness. [[spoiler: AndManGrewProud and attempted to raise a third sun, transforming the known world into a wasteland when it crashes down.]] Hence, the campaign taking place AfterTheEnd is called "Under the Burning Suns" and the new day/night cycle becomes an important game mechanic.
* There are QUITE a lot of these present in ''Videogame/EliteDangerous''. Much like the rest of the layout of the galaxy, the setup is extremely realistic; binary (or even trinary) systems can have a ''lot'' of distance between their respective stars, and typically have a whole host of planets, moons, and stations orbiting each one. Unfortunately, this can make traveling through such a system a royal pain in the ass, if the stars are far enough apart.
* In ''VideoGame/EVEOnline'', every system is at least binary system due to the unique gravity interactions needed to make a stable jump gate. The initial gate from Earth was named EVE and was due to the sudden appearance of a wormhole in the solar system.
** However, the developers seem to have forgotten this piece of background, as no system in the EVE cluster actually has more than one star (perhaps the other stars are all brown dwarfs and/or orbit very far from the other star?). However, in wormhole space, binary systems are common (although the second star exists only as a background texture rather than an object you can warp to).
* A binary system features prominently in ''VideoGame/FreeSpace2'', during a mission deep behind enemy lines. The player's commander remarks that he'd like to get out of there ASAP, because "binary systems give me the creeps."
* In ''Videogame/LittleBigAdventure'' the protagonist's home planet is called Twinsun, because it is situated between two suns.
* From ''Videogame/PerfectDark'', the Skedar homeworld is part of a trinity star system.
* It's sort of hard to notice, as the smaller, white one is likely to be obscured by the buildings or mountains, but the Lungfishopolis level in VideoGame/{{Psychonauts}} has two suns.
* ''Videogame/SidMeiersAlphaCentauri''. See RealLife below for a bit of further information.
** Chiron--also called "Planet"--the planet where humans land, orbits Alpha Centauri A alone. Chiron is in a Type III situation. Alpha Centauri A and B orbit each other in a relatively close and mildly eccentric elliptical orbit, with them coming closest to each other (periastron) at about 11 AU (roughly the distance between the Sun and Saturn) and furthest apart from each other (apastron) at about 35 AU (roughly the distance between the Sun and Pluto); any planet orbiting in Alpha Centauri A's habitable zone would thus receive a non-negligible amount of light and heat from B (and vice-versa). Since the developers [[ShownTheirWork did their homework]], whenever Hercules (Alpha Centauri B) reaches periastron, the native life on Planet experiences tremendous growth. There are also two moons: Nessus and Pholus.
* A little camera trickery in ''VideoGame/TheSims 2'' reveals this to be the case for Sim Earth. Which may or may not explain a few things.
* Some systems in ''Videogame/{{Spore}}'' are Type 1. Habitable planets in such systems are typically farther away from the two suns, especially if one or both are blue stars. Since a planet in such a system would be getting illumination and consequently heating from both stars, and blue stars are the brightest and hottest stars of all, [[ShownTheirWork this makes a lot of sense]].
* ''VideoGame/{{Freelancer}}'''s Sirius Sector consists of dozens of star systems, many of which are binaries or more. Most of them [[SceneryPorn look drop-dead gorgeous]].
* In ''Videogame/{{Super Mario Galaxy}}'', the aptly-named [[LethalLavaLand Melty Molten Galaxy]] consists of several mostly-lava planetoids that are sandwiched between two ''very close'' stars. Very close, as in probably no more than a couple miles apart.
* When in Dry Dry Desert in ''VideoGame/PaperMario64'', take a close look at the background during a battle: the Sun is crossing it slowly, but before it goes down on the right, ''another'' one is already rising of the left, meaning two suns can be seen in the sky ''simultaneously''.
* ''Videogame/{{Unreal}}'''s Na Pali orbits two suns.
* ''{{VideoGame/Touhou}}'': The Chinese legend of Houyi mentions the Earth once had ''nine'' suns, which threatened to burn the earth until he shot down all but one. In the game's backstory, however, one of them landed on and killed Junko's son, who has now become pure vengeance, killing Houyi and trying to kill his wife Chang'e.

[[folder:Web Original]]
* The ''Blog/WhatIf'' blog mentions Types I and II of this trope, calling them "circumbinary" and "[[BuffySpeak the other kind]]", while [[http://what-if.xkcd.com/150/ discussing]] [[AlienSky how would rainbows form on a planet with two suns]].

[[folder:Western Animation]]
* In ''WesternAnimation/{{Bravestarr}}'', the planet New Texas has a "sky of three suns".
* In ''WesternAnimation/{{Fangbone}}'', Fangbone's homeworld, Skullbania, has three suns.
* An early episode of ''WesternAnimation/{{Futurama}}'' had the characters delivering a package to Trisol, a planet [[ExactlyWhatItSaysOnTheTin with three suns]].
* In ''[[WesternAnimation/AdventuresOfTheGalaxyRangers Galaxy Rangers]]'', the planet Granna is like this.
* ''WesternAnimation/StarWarsTheCloneWars'': Besides TropeCodifier Tatooine appearing several times, the show also has water world Mon Cala.
* ''WesternAnimation/StarWarsRebels'':
** [[Recap/StarWarsRebelsS3E02TheAntillesExtraction "The Antilles Extraction"]] is set on the binary-star-orbiting planet Montross.
** {{Discussed|Trope}} in [[Recap/StarWarsRebelsS3E09VisionsAndVoices "Visions and Voices"]]. Kanan, Ezra and Sabine discover that [[spoiler: Obi-Wan Kenobi is still alive and]] living on a planet with twin suns. [[TheSmartGuy Sabine]] points out that that piece of information doesn't narrow the field of possible planets down much, because it turns out that in the ''Franchise/StarWars'' galaxy, as in real life, binary systems are extremely common.
** Unsurprisingly, the episode [[Recap/StarWarsRebelsS3E18TwinSuns "Twin Suns"]] features this, specifically [[TropeCodifier Tatooine's]].
* The planet Prysmos in ''WesternAnimation/{{Visionaries}}'' has ''three'' suns and their alignment is what triggers a new Age of Magic.

[[folder:Real Life]]
* In any patch of the sky where you look at night, most of the points of light you'll see are binary or larger star systems -- single-star systems, like ours, are relatively rare in comparison. The problem is rather whether a more or less Earthlike planet could exist there.
** It has been hypothesized that our Sun has a faint companion star (a white, red, or brown dwarf), orbiting the Sun at a distance of about one light year. (The star was originally proposed to explain the apparent periodicity of extinction events; it even received an [[MeaningfulName apt nickname]]: [[http://en.wikipedia.org/wiki/Nemesis_(star) Nemesis]].) However, recent space-based infrared surveys have confirmed that there is no such object within two lightyears.
* The Alpha Centauri (Rigil Kentaurus) system, consisting of two yellow dwarfs, A and B. B is the somewhat smaller member of the duo. Additionally, [[http://en.wikipedia.org/wiki/Proxima_Centauri Proxima Centauri]] is believed to orbiting Alpha A and B, which would make this a ''Trinary'' Sun for any planet around. Reality is unrealistic.
** There is a planet around Alpha Cen B, AC Bb, but it is so close to Alpha Cen B that it receives thousands of times more light from B and A and is baked into lava.
** From any planets of Proxima Centauri (0.21 light years away), A and B appear as stars, just a bit brighter than Venus from Earth. Proxima itself would be barely naked-eye visible from a planet of A or B.
** Viewed from a planet orbiting ''any'' star in the Alpha Centauri system, Sol would be a respectably bright star (about as bright as Vega looks on Earth) in the constellation Cassiopeia.
* Zeta Reticuli is a Binary Star System made up of Zeta1 and Zeta2 Reticuli.
* In 2011, scientists discovered [[http://en.wikipedia.org/wiki/Kepler_16b Kepler 16b]] which is not a binary star... but a planet in stable orbit around a binary star system. It's been nicknamed [[Franchise/StarWars Tatooine]]. Since then, several similar systems have been found.
** Spoofed in [[http://planetquest.jpl.nasa.gov/system/media_files/binaries/72/original/Kepler_16b_screen_small.jpg this mock travel poster]] from the Jet Propulsion Laboratory.
-->''Relax on Kepler-16b, the land of two suns. Where your shadow always has company.''
* Enter the nearby triple system [[https://en.wikipedia.org/wiki/Gliese_667 Gliese 667]], whose third star (Gliese 667C) has at least two planets orbiting it, one of them in the habitable zone.
* Polaris, the North Star, is actually a triple star system consisting of a super giant, a main sequence star larger than the Sun, and a dwarf star.
* In 2012 Planet Hunters discovered PH-1, orbiting a binary system orbiting a binary system. The result? '''PH-1 HAS FOUR SUNS.''' It has been nicknamed "Tatooine times two."
** The main sun is a yellow star, much brighter than our sun. The secondary sun, a red dwarf, is a quarter as bright as our sun. And the other, similar pair of stars (about 0.02 light years away) are many times brighter than Venus, and easily visible in daytime.
* And it doesn't stop there. [[http://en.wikipedia.org/wiki/HD_139691 HD 139691]] consists of six stars, as does [[http://en.wikipedia.org/wiki/Castor_(star) Castor]], and [[http://en.wikipedia.org/wiki/Nu_Scorpii Nu Scorpii]] is believed to contain as many as seven in one system.
* Recently published research based on the discovered planets of multi-stellar systems suggests that it would be entirely feasible for such planets to occupy stable orbits in habitable zones, both around one star of the system or in complex orbits between two or more stars.