Fictional planets of the Solar System

Vulcan was a hypothetical planet supposed to revolve around the Sun inside the orbit of Mercury, invoked to explain certain irregularities in Mercury's orbit. The planet was proposed as a hypothesis in 1859, and abandoned not later than 1915.

• "Vulcan's Workshop" (Astounding Stories, June 1932), short story by Harl Vincent: a penal colony is located on Vulcan.[1][2]
• "At the Center of Gravity" (Astounding Stories, June 1936), short story by Ross Rocklynne: two people are trapped inside a hollow Vulcan.[3]
• Vulcan is part of the Solar System in the Captain Future series. Despite being said to be covered in magma, in Outlaw World (1946) it is discovered that it is hollow and inhabited inside.
• Mission to Mercury (1965), science fiction novel by Hugh Walters. During the return of the first crewed flight to Mercury, a crew member notices a dark spot moving across the Sun. Since the spot is between them and the Sun and appears to be moving to the naked eye, it can only be the previously-hypothetical Vulcan; it must be moving rapidly and extremely close to the Sun.
• Vulcan is visited in the 1882 novel A Thousand Years Hence by Nunsowe Green.[4]
• Sailor Moon musicals (1993–2005): A planet called Vulcan along with its moon, Astarte, is said to be on the other side of the Sun.

The name "Vulcan" has been used for various other fictional planets, in and out of the Solar System, that do not correspond to the hypothetical planet Vulcan. The planet Vulcan in the Star Trek franchise, for instance, is specified as orbiting 40 Eridani A.

Counter-Earth was a hypothetical planet sharing an orbit with Earth, but on the opposite side of the Sun (hence Earth and Counter-Earth would always be invisible to each other). The idea of a counter-Earth has never been a serious scientific hypothesis in modern times.

Phaëton is a name given to a supposed planet existing in the past between the orbits of Mars and Jupiter, which no longer exists, having become the Solar System's asteroid belt. Proposed not long after the discovery of multiple asteroids at the beginning of the 19th century, the idea that the asteroids were fragments of a single planet was gradually abandoned over the course of the middle decades of the 20th century in favor of the conclusion that no planet had ever accreted in the region of the asteroid belt in the first place.

In fiction, various other names were given to the same or similar concepts.

• Seola (1878), novel by Ann Eliza Smith: mentions the existence of a Wan Planet, "a great planet between the Red World [Mars] and the Green [Jupiter]; uninhabited, cracked, and fissured, deep-seamed and rent by volcanic fire. Deep, jarring, splitting sounds now issue from the centre of this desolate orb : it is about to fall in pieces. Its disruption will endanger the Earth",[9] leading to the deluge of Genesis.
• "Time Wants a Skeleton" (Astounding Science Fiction, June 1941), short story by Ross Rocklynne: characters travel through time to Phaeton, an Earth-like planet, just before it was destroyed in a collision with another (unnamed) planet.
• "The Lost World of Time" (Captain Future Magazine, Fall 1941), a Captain Future story by Edmond Hamilton: characters travel through time to the planet Katain and rescue the inhabitants before it was destroyed. Adapted to Japanese anime in 1978, where the planet is named Prometheus.
• Et la planète sauta... (1946), novel by B. R. Bruss, tells of a planet that once existed between Mars and Jupiter called Rhama.
• Space Cadet (1948), juvenile novel by Robert A. Heinlein. The hero's first assignment after graduation from the Space Patrol's academy is to a ship charting the intractable Asteroid Belt. He has the luck to be involved in a startling discovery: not only is the Belt proven to be what is left of an exploded planet Lucifer, but also remains are found of that planet's inhabitants, who had been responsible for its destruction.
• In "Letter to a Phoenix", (1949), a short story by Fredric Brown, it is mentioned that one of the human civilizations which existed before has destroyed the fifth planet, named Skora.
• Return to Mars (1955) juvenile novel by W. E. Johns. The fifth planet, called Kraka, was accidentally destroyed in a nuclear experiment carried out by its inhabitants.
• Chikyu Boeigun (The Mysterians, 1957). A newly discovered asteroid in the asteroid belt is the Mysterians' home planet, Mysteroid, rendered uninhabitable as the result of a nuclear war.
• Rogue in Space (1957), novel by Fredric Brown. A living, intelligent, asteroid collects all the asteroids in the Belt and forms them into a planet with himself at its centre. In this variant, the fifth planet exists not in the past but in the future.
• Fallen Star (1959), novel by James Blish. The fifth planet, called Nferetet, may have been destroyed by the Martians because they saw its inhabitants as a threat.
• Stranger in a Strange Land (1961), novel by Robert A. Heinlein. An unnamed fifth planet was destroyed by Martians after they deemed its inhabitants too barbaric to be allowed to exist. "[The Martians] encountered the people of the fifth planet ... and had taken action; asteroid ruins were all that remained."[10]
• Keith Laumer's Worlds of the Imperium (1962) features, among a great variety of alternative history timelines. several in which Earth was broken up and its fragments scattered to make an asteroid belt.
• The protagonist of Poul Anderson's The Corridors of Time (1965), who becomes involved in the war of two mutually-antagonistic factions from the far future, finds that an earlier phase of the war between them caused the planet Mars to break up into an asteroid belt. This cataclysm forced the two contending parties to adopt more subtle methods of warfare, mainly involving time travel.
• In Das Zeitauge[11] (1966), a novel by H. G. Ewers,[12] Zeut, the fifth planet of the Sun in the Perry Rhodan Universe,[13] was destroyed by aggressive aliens, 50,068 B.C.. Also in the anthology Lemuria.[14]
• In "Destination: Saturn", (1967), a novel by Donald Wollheim writing as David Grinnell, and Lin Carter, an ancient spaceship created by the dead occupants of the fifth planet is found to contain many weapons useful to Earth in its war against Saturn. The novel also features a visit to a moon of Jupiter found to have been part of the former planet's core, and a discussion of its destruction.
• Brian Lumley's story collection The Caller of the Black (1971), which contains many contributions to the Cthulhu Mythos, references Thyoph, a planet originally orbiting between Mars and Jupiter that was destroyed by an aspect of Azathoth.
• "The Ultimate Crime" (1976), a short story by Isaac Asimov, was actually based on the author's essay to qualify for entry into the Baker Street Irregulars, a group of Sherlock Holmes enthusiasts. In it, he speculates that Professor Moriarty's The Dynamics of an Asteroid was a scholarly work that attempted to compute how the hypothetical fifth planet had exploded, and how to repeat the effect on Earth.
• Inherit the Stars (1977), first in the Giants series of novels by James P. Hogan. The planet Minerva exploded due to nuclear war 50,000 years ago to form the asteroid belt with the largest remnant thrown out of Minerva's orbit to form Pluto. It was home to two intelligent races: the Giants 25 million years ago, and the Lunarians (nearly identical to modern man) 50,000 years ago. Also mentioned in the novels The Gentle Giants of Ganymede (1978), Giants' Star (1981), Entoverse (1991) and Mission to Minerva (2005).
• In L. Neil Smith's The Venus Belt (1980), an alternate history space-faring Libertarian society deliberately blows up the planet Venus, with the reasoning that due to its extreme heat the intact planet is completely useless to humans while if Venus is broken up into a new asteroid belt it could open up great mineral wealth.
• In the Doctor Who story Image of the Fendahl (1977) the fifth planet was the home of the Fendahl, a malevolent entity that consumed all life. The Time Lords placed the planet in a time loop in the hope of imprisoning the creature, but it escaped and arrived on Earth 12 million years ago in the form of a human skull.
• Andromeda Stories (1980–1982) by Keiko Takemiya & Ryu Mitsuse: a pair of robot characters who hail from Phaeton have been sent to explore the Andromeda galaxy, and find their home planet destroyed upon their return.
• Gall Force 2: Destruction (1987), depicts the 5th planet, Damia, is in fact a massive super weapon, the System Destroyer, intended to act as a trap to destroy the two opposing forces. It is sabotaged and destroyed, resulting in the current asteroid field.
• In Frank Chadwick's Space: 1889 RPG Steampunk system (introduced 1989), Vulcan is the ancient home to the Vulcan race, and was positioned between Mars and Jupiter. Its destruction (due to being old; increasing distance from the Sun symbolizes evolutionary progress) created the asteroid belt.
• Faety (The Destruction of Faena), 1989 novel by Alexander Kazantsev. In this adaptation of Shakespeare's Romeo and Juliet, the asteroid belt is the debris of Faena, the fifth planet of the Solar System located just between Mars and Jupiter. Faena was destroyed thousands of years before the first civilizations of Earth appeared, following the activation of a doomsday device-like thermonuclear super weapon built by the native sentient species and the few of them who survived the explosion (by launching into space) had to seek refuge on Mars and Earth. The homo sapiens genus is thus assumed to be a mixture of local DNA and the Faetan genes.
• Starting with a Swamp Thing story by Doug Wheeler in 1991, stories from DC Comics proposed that a former fifth planet was the original home of all fungal life (and a fungal group mind, The Grey), which migrated to Earth on a meteorite.
• Mutineers' Moon (1991), novel by David Weber. The asteroid belt was a planet that was geologically unstable. The Achuultani attacked the planet with kinetic weapons, shattering it, and then attacked Earth, resulting in the extinction of the dinosaurs.
• Final Fantasy IV (1991), video game. The fifth planet is populated by a race of highly advanced humanoids who are aware that their planet is unstable. Thus they travel to Earth and craft a second moon to live on as the fifth planet explodes to create the asteroid belt. The character FuSoYa is a member of this race, which is called the Lunarians due to their living on the moon (the true name of their race is not said).
• The Werewolf: The Apocalypse roleplaying game (introduced 1992) names the former planet Turog, governed by a planetary incarna (concept spirit) named Rorg the Hunter.
• End of an Era (1994), Robert J Sawyer. A time travel novel that explores the idea that Phaeton was not yet destroyed when this story takes place.
• Ocean (2004), comic by Warren Ellis: discusses the possibility of an ancient proto-human culture originating on Phaeton.
• "The Four-And-A-Halfth Planet" (2006) by Sam Hughes describes a planet, Tjörd, that formed from the current asteroid belt while the Earth is destroyed and becomes a new asteroid belt in an alternate timeline.
• Exiles #4 (June 2008): When the super hero group known as Exiles travel to a parallel dimension, they find out there is no asteroid belt, but a planet called Hera, which humans have not terraformed yet, although they have already terraformed Venus and Mars.
• The manga series Terra Formars (introduced 2011), regularly mentions a planet named Rahab that once existed between Mars and Jupiter that was shattered following a cometary impact.

Fictional planets in the Solar System beyond the orbit of Neptune have been employed many times as settings or references in science fiction. Following the general reception of Pluto as the ninth planet of the Solar System in 1930, a hypothetical additional planet was sometimes called a "tenth planet". Since 1992, a very large number of objects have been found beyond Neptune; all the objects in the following list, however, are purely fictional. Common names for trans-Neptunian planets in fiction include Planet X, after a planet once believed to lie beyond Neptune, Persephone (or Proserpina), after the wife of Pluto, and Minerva, after the Roman goddess of wisdom and education (which would fit with a planet discovered through mathematical predictions rather than direct observation).

• Monster Zero (怪獣大戦争, Kaijū Daisensō {{literal translation|The Giant Monster War[18]) (1965), the 6th Godzilla film: Aliens from Planet X (located between Jupiter and Saturn) try to conquer the Earth using Godzilla, Rodan, and King Ghidorah to take its water supply because water is scarce on their planet.
• The Lost Planet (1953) describes journeys to "Hesikos", a fictional asteroid with highly eccentric orbit whose humanoid inhabitants renounced nuclear power after a meltdown, but have meanwhile developed broadcast telepathy. A happy ending ensues when Earthmen provide safe nuclear technology in return for thought projections from Hesikos to reduce fear and aggression here.
• Twin Earth: a hypothetical duplicate of the Earth and everything on it (in an unspecified location), as a thought experiment by philosopher Saul Kripke about names: the fact that everything you could say about someone or something on the Earth would be equally true of its counterpart on Twin Earth shows that names can't merely be shorthand for descriptions, as they may not uniquely identify a person/object.
• The short story "The Mysterious Finding" ("Загадочная находка") by Vladimir Obruchev (1947) features the discovery of an artificial meteorite containing the last message of a race living on a planet similar to Phaeton, though it used to be located between Earth and Mars. By the time the log is written, it is months away from being destroyed by a critical destabilization caused by nuclear bombardment of an extinct volcano.

Rogue planets in fiction usually originate outside the Solar System, but their erratic paths lead them to within detectable range of Earth. In reality, no rogue planet has ever been detected transiting the Solar System.

• When Worlds Collide (1933), novel by Philip Wylie and Edwin Balmer: Extrasolar planets Bronson Alpha and Bronson Beta enter the Solar System: Bronson Alpha destroys the Earth, Bronson Beta assumes its orbit.
• Flash Gordon (1934), comic by Alex Raymond: Rogue planet Mongo threatens to collide with Earth.
• Super-Neutron (1941) short story by Isaac Asimov, where it is claimed that a rogue planet could cause the Sun to explode.
• The Man from Planet X (1951) is an early space-alien film. In the film, the orbit of the hitherto unknown extrasolar Planet X brings it close to Earth.
• Warning from Space (1956), sci-fi film by Daiei: The rogue planet Planet R enters the solar system on a collision course with Earth. Fortunately, its arrival is detected by the Pairans, residents of a Counter-Earth planet who send an envoy to inform humanity of the threat. At the last minute, a nuclear device is developed and deployed, destroying Planet R and saving the Earth.
• Fifth Planet (1963), sci-fi novel by Fred Hoyle and his son Geoffrey Hoyle: Another star is due to pass close to the Sun, close enough for conventional spacecraft to reach it. The first planets observed are four gas-giants, but then an inner 'Fifth Planet' is found. It shows signs of life, and rival Russian and US expeditions are launched to visit it.
• The Tenth Planet (1966), serial of the Doctor Who TV series: An extrasolar planet, Mondas, enters the Solar System beyond Pluto, making it temporarily the tenth planet. It originated in the Solar System with an orbit near that of Counter-Earth before the native Cybermen powered it with an engine and moved it out of the Solar System.
• Breakaway, the first episode of the mid-1970s sci-fi series Space: 1999, involved an exploration of a rogue planet named Meta.[19]
• Transformers (1984) toys and spinoffs: Cybertron is a robot-inhabited rogue planet that comes close to Earth. In the Generation One cartoon timeline, this only occurs after the events of the three part episode The Ultimate Doom, in which Cybertron is brought into Earth's solar system (and specifically into Earth's actual orbit) by the use of a space bridge big enough to transport the entire planet. Afterwards, it is shown to exist somewhere reasonably close to Earth's Solar System after it is pushed out of Earth's orbit. Characters such as Starscream, Omega Supreme, and Astrotrain are later shown to be able to travel from Earth to Cybertron and back with relative ease depending on the plot of the story. Later incarnations of Cybertron are either rogue planets or else have a method of near instant transportation to and from Earth.
• Sunstorm (2005), an alien race from a planet in orbit around Altair sends a rogue Jovian planet into the Sun, setting the stage for a solar storm intended to wipe out humanity in the year 2042.
• Melancholia (2011), a planet emerges from behind the Sun and approaches Earth, initially passing by, before coming back on a collision course. It was written and directed by Lars von Trier.

Clicking on a planet leads to the article about its depiction in fiction.

• Discovery and exploration of the Solar System