Binary Suns

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A trope where a planet has two suns in the sky. Occurs primarly in sci-fi settings, but certainly isn't limited to it.

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 above/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 an endless day.
  • 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.

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.[1]

A subtrope of Alien Sky. Can occasionally fall into Artistic License Astronomy, depending on the behavior and depiction of the suns.

Their prevalence in science fiction is actually an example of Reality Is Unrealistic, because binary stars are in fact much more common than single stars like our Sun,[2] although it is uncertain how likely it is that habitable planets would form in the presence of two suns.

Examples of Binary Suns include:

Anime and Manga

  • Planet Namek in Dragon Ball has three suns, and perpetual daytime because at least one of them is always in the sky at any given time.
  • In Trigun, Gunsmoke is a desert world with twin suns.
  • In the later part of Braiger, and throughout its sequels Bikezinger & Sasuliger, the Solar System becomes a binary star system after Big Bad Carmen Khamen uses the J9 robots' size-changing "Synchron System" to increase Jupiter's mass to the point where it can sustain nuclear fusion.

Collectible Card Games

  • In Magic: The Gathering, 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 made of pure mana.


Comic Books

  • In the Marvel comics, The Transformers' homeworld of 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.

Film

Literature

  • Norfolk in Peter F. Hamilton's Night's Dawn Trilogy 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.
  • Technically the Manticore system from Honor Harrington with Manticore and Sphinx orbiting Manticore-A while Gryphon orbits Manticore-B. However they are a what's called a distant binary with enough separation that Manticore-B would just be a very bright star in Manticore and Sphinx's night sky.
    • A similar situation (with only one habitable planet per sun) in the Pontifex system in the Talbot 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
    • Honor Harrington 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.
  • Helliconia is set in a binary system, with the titular 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 civilisation.
  • Isaac Asimov's 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.
    • 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.
  • 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'.
  • Arthur Dent is impressed by watching a twin sunset from Magrathea in The Hitchhiker's Guide to the Galaxy. Marvin is a little more jaded.
  • Arthur C. Clarke's Childhood's End 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.
  • 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 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.
  • The planet Placet in Fredric Brown'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 hallucinations. This is only one of the reasons why it is considered crazy.
  • 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.
  • Darwin IV, the planet described in Wayne Barlowe's Expedition, has twin suns. The term "sunslight" is used several times in the text, the better to remind readers of this.

Live Action TV

  • A Star Trek: The Next Generation episode called "Night Terrors" is set in a binary system.
  • Angel: The two suns in Pylea.
  • In an episode of Sesame Street, Elmo read to María a story he wrote and illustrated about an imagined trip to a planet with two suns in its sky.
  • Oz (excuse me, "Outer Zone") in Tin Man has dual suns and several moons.
  • In Doctor Who, the Doctor's homeworld Gallifrey is part of a binary star system.
  • Stargate SG-1 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 Shout-Out to Arthur C. Clarke's novel 2010: Odyssey Two, wherein the same is done to Jupiter.
  • The Tomorrow People briefly mentioned a planet called QX5 that orbited two suns.

Tabletop Games

  • R. Talsorian's 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.

Video Games

  • Irdya, the world of The Battle for Wesnoth, originally has only one sun, but another is raised to banish the darkness. And Man Grew Proud and attempted to raise a third sun, transforming the known world into a wasteland when it crashes down. Hence, the campaign taking place After the End is called "Under the Burning Suns" and the new day/night cycle becomes an important game mechanic.
  • Sid Meier's Alpha Centauri. See Real Life below.
    • Chiron, the planet where humans land, orbits Alpha Centauri A. Whenever Hercules (Alpha Centauri B) reaches perihelion, the native life on Planet experiences tremendous growth. There are also two moons: Nessus and Pholus.
  • Some systems in 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, this makes a lot of sense.
  • A binary system features prominently in Free Space 2, 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 Little Big Adventure the protagonist's home planet is called Twinsun, because it is situated between two suns.
  • From Perfect Dark, the Skedar homeworld is part of a trinity star system.
  • Unreal's Na Pali orbits two suns
  • 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 Psychonauts has two suns.
  • In Super Mario Galaxy, the aptly-named 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.
  • In EVE Online, every system is at least binary system due to the unique gravity interactions needed to make a stable jump gate. The initial fate from Earth was named EVE and was due to the sudden appearance of a wormhole in the solar system.

Western Animation

Toys

  • In Metru Nui there are two suns. 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".

Real Life

  • The Alpha Centauri (Rigil Kentaurus) system, consisting of two yellow dwarfs, A and B. B is the somewhat smaller member of the duo. Additionally, Proxima Centauri is believed to orbiting Alpha A and B, which would make this a Trinary Sun for any planet around. Reality is unrealistic.
    • However, only A and B would look like suns from each others' planets. From a planet of Proxima (0.21 light years away), A and B appear as stars, just a bit brighter than Venus from Earth. Proxima itself would be barely 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.
    • Nancy Lieder claims that, according to the aliens from Zeta Reticuli who talk to her on a regular basis, Zeta Reticuli is actually a hexary star system (i.e. a system with 6 suns). They're miraculously lined up such that four of them are always hidden behind the other two, however.
  • 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. The problem is rather whether a more or less Earthlike planet could exist there.
    • While most of the brighter stars are indeed binary suns, the vast majority of stars in the Sun's local neighborhood are solitary red dwarfs too dim to be seen without a telescope. Presumably, the rest of the Milky Way is also populated as such.
  • 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 apt nickname: Nemesis.)
  • In 2011, scientists discovered Kepler 16b which is not a binary star... but a planet in stable orbit around a binary star system, something previously thought impossible or at least, highly unusual. It was long thought that for such a planet's orbit to be stable, the planet "... belonging to two stars at once would have to be at least seven times as far from the stars as the stars were from each other. According to that, Kepler 16b would have to be twice as far out as it is to survive." It's been nicknamed Tatooine.
  • 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.
  • And it does not stop at two or three stars. HD 139691 contains six stars and Nu Scorpii is believed to contain as many as seven, in one system.
  1. ↑ Brief figure 8 orbits are possible -- the free-return trajectories flown on the Apollo missions were figure 8s -- but these are never stable.
  2. ↑ At least, when dealing with stars comparable in size and intrinsic brightness to the sun. Among the smaller, dimmer, and much more numerous red dwarf stars, solitary red dwarfs are actually more common than binary red dwarfs.
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