"Planet" is a term whose etymology originates from the Greek word for "wanderer" — and while most planets in fiction can be found "wandering" in orbits around a star (or multiple stars), this one truly is wandering — completely alone.
It wanders across the universe silently, without the light of a sun to provide heat. For obvious reasons these planets tend to be Single Biome Planets of the frozen and dark varieties, although if they're covered in a thick ice sheet, life might flourish in liquid oceans heated by the planet's core — a moon orbiting one of these planets might also get enough energy from tidal forces to have a liquid interior.
If the planet was not always a lone wanderer, ruins of civilization might be found on it — dry cold is one of the best means of preservation we know of today, and ruins will thus be preserved for a very long time. Typically, the fact that the planet was flung away doesn't bode well for the civilization once found on it, though examples do exist where the original inhabitants managed to perform a Homeworld Evacuation, as well as ones where its inhabitants proved durable enough to survive such a grim fate.
If one of these is deliberately built by a civilization, usually a Higher-Tech Species, possibly because their original sun was killed, or died and they wanted to Outrun the Fireball, it's a Planet Spaceship. See also Big Dumb Object, which may be mistaken for one of these at first glance. If the planet moved itself out of orbit, you might be dealing with a Genius Loci.
- Remina: The titular planet emerged from a wormhole sixteen light-years away from Earth in a corner of the Hydra constellation and was observed to have an erratic, zigzagging orbit where stars around it vanish, until a scientist noticed that it turned around to the solar system's direction and made its way in a direct path. That's because it's alive and both an Eldritch Location and Abomination.
- Queen Millennia: The Tenth Planet La-Metal has been cycling to and from Earth every 1000 years on a wide orbit since at least the era of trilobites. It's explained by a deified "Black Sun" Lar orbiting parallel to the Solar System and dragging La-Metal behind.
- The Marvel Universe features a villain known as Ego the living planet. As his name states, Ego is a sentient planet that is able to move freely and absorbs other planets and space vessels to survive.
- The Time Runs Out arc of The Avengers (Jonathan Hickman) involves a rogue planet on a collision course with Earth. An Iron (Wo)man from the year 3030 travels back in time to Set Right What Once Went Wrong and averts an evacuation of Earth by setting up machines to phase the whole planet into Earth and draw upon it as an energy source needed for an upcoming crisis. The disturbing part is that they're told the planet was thrown at the Earth, begging the question what being is capable of such a feat.
- Evacuate Earth has a rogue neutron star on a collision course with our solar system, which will destroy Earth and presumably all of the other planets as well. Humanity has 75 years to build The Ark and get away before it arrives.
- The Green Slime: The plot occurs because a rogue planet called Flora wanders into the Solar System in a direct collision course with Earth, forcing the protagonists to set foot on it and blow it to smithereens and as a result getting their suits infected with bits of the titular Blob Monster.
- Melancholia: The titular blue gas giant is a rogue planet that collides with Earth at the end (and the beginning) of the film.
- The Phantom Planet has a goofy B-Movie take on the subject. Rheton, the wandering planet of the title, has a population of tiny Human Aliens living on it — and when astronaut Frank Chapman lands, breathing the atmosphere makes him shrink to the size of the locals as well.
- The Wandering Earth: The backstory involves humanity turning Earth into one of these, by way of adapting it into a Planet Spaceship to escape the looming death of our sun. The plan is to one day reach Alpha Centauri, but the voyage will take thousands of years.
- In Foundation and Empire, Bel Riose sets his headquarters on a rogue planet during his war with the Foundation.
- Another Isaac Asimov novel Nemesis has the eponymous red giant threatening Earth's solar system. Some parts of the colony on a space station orbiting it are fine with this, others generally aren't aware (it's not an immediate threat, and realizing the danger requires actually calculating where Nemesis is moving in relation to Sol).
- In Frontlines, the Washington ends up near a rogue planet after accidentally hitching a ride on a Lanky seed ship's Alcubierre drive. The rogue planet itself is a fairly ordinary gas giant, but one of its moons experiences enough tidal heating to be warm, wet, and habitable, though it is still utterly dark. This moon, "Green," is crawling with Lankies and may well be their homeworld.
- In Have Space Suit – Will Travel Wormface's planet gets turned into this by the Three Galaxies Council. Kip figures, okay, exile: it's rough justice but fair; they were going to turn Earth into a human meat ranch after all. The Mother Thing (a Galactic operative) sets him straight: "You do not understand, dear gentle Kip- they do not take their star with them."
- In A Pail Of Air by Fritz Leiber Earth itself becomes this, as it is torn off its gravitational moorings and ripped away from the Sun by a wandering dead star.
- Red Dwarf: In Better Than Life, the Earth itself ends up as one of these: after being reduced to a dumping ground for the rest of the solar system, a catastrophic chain reaction of methane storms, a crashing garbage scow and several abandoned nuclear power plants farts the entire planet out of orbit and into deep space.
- In the Star Carrier books, the Glothr homeworld of Invictus is one of these, floating through intergalactic space. It is cold, dark, and airless, but that’s no problem for the Glothr, who live in the much warmer (but still glacially cold) ammonia-saltwater sea far beneath its frozen surface.
- Star Trek: The Original Series: In Planet of Judgment, the U.S.S. Enterprise encounters a rogue planet which has a small black hole in orbit around it.
- When Worlds Collide involves the discovery of two planets, Bronson Alpha and Beta, wandering into the Solar System, and the increasing worldwide panic when it's figured out that the bigger of the two will impact Earth directly.
- In The Long Way to a Small Angry Planet, the crew of the Wayfarer happen across a rogue planet inhabited by a colony of heretic outcast Sianats. They stop for some simple repairs, but their own straight-and-narrow Sianat Pair crew member is considerably distressed by the visit.
- Chris Beckett's Eden trilogy is set on a rogue planet where, in the absence of sunlight, the bio-luminescent native plant life is based on geothermal energy.
- In Ramsey Campbell's "The Tugging," the Outer God Ghroth is a rogue planet that drifts through space. Its song, the "music of the spheres," can awaken every Eldritch Abomination on each world it passes.
- The old Star Wars Legends expanded universe featured one of these in the sentient planet Zonama Sekot. First introduced in the aptly-named Star Wars: Rogue Planet, Zonama Sekot was a seed of the Yuuzhan Vong homeworld Yuuzhan'tar, which found its way from the Vong's home galaxy to the setting of the Star Wars universe. Sometime shortly after the events of Star Wars: Episode I – The Phantom Menace, the planet was attacked by Tarkin (yes, that Tarkin) and up and fled into hyperspace. The planet continued to wander for some 30-odd years before Luke and Mara led an expedition to track it down, and determine just what its connection was to the Vong. They ultimately enlisted the planet's aid in putting an end to the war.
- Poul Anderson's Satan's World features one of these (excerpt available here). This one's special because it's a rogue planet temporarily passing by a star, heating it up enough to give it an atmosphere and hydrosphere while still leaving it colder than a habitable planet. This would make it a good place to build Transmutation plants on, which produce so much waste heat that a planet-sized heat sink is needed.
- Doctor Who: The Cybermen were originally from the planet Mondas, Earth's twin planet, which somehow was knocked out of its orbit and drifted into space. As the planet froze, they had to slowly convert themselves into cyborgs to survive, which corrupted them.
- Space: 1999 deals with the perils the people of Moonbase Alpha endure when a massive nuclear explosion kicks the Moon out of orbit and wanders thru the galaxy on its own volition, courtesy of running into wormholes and other phenomena. Played With in that while it's not outright a planet, it still hits the trope's notes of civilisation facing adversity (not to mention that there are planets smaller than the Moon).
- Star Trek:
- Star Trek: The Original Series: Gothos (which may have been created by Trelane).
- Star Trek: Deep Space Nine: The Changeling homeworld is an M-class rogue planet inside the Omarion nebula. How the planet supports life is never explained.
- Star Trek: Enterprise: "Rogue Planet" features such a world, called Dakala. It's a Minshara-class planet with a breathable atmosphere and a temperate climate, provided by hot gasses venting from its interior. It somehow has plant life despite not having anything to power photosynthesis.
- Super Sentai/Power Rangers:
- One of these showed up in the first episode of Kyōryū Sentai Zyuranger; it was called "Nemesis" and was the location of Bandora's imprisonment. Two Japanese astronauts who went to investigate accidentally set Bandora and her forces free.
- This was carried over into Mighty Morphin' Power Rangers, though in the 2010 reversioning they tried to make it more moon-like (since the original 1993 version hadn't explained what the planetoid wasnote ). The establishing shot of it was reused as the "Cimmerian planet" for the first episode of Power Rangers in Space.
- ROGUEMAKER features one, which is referenced in plain sight in the show's title.
- Delta Green has an adventure in its original corebook in which the mi-go are bringing the rogue planet Outer God called Ghroth to Earth for uncertain purposes.
- Dungeons & Dragons:
- The Elder Evil known as Atropus, the World Born Dead, is an Undead Abomination in the shape of a planetoid, which roams the universe in search of inhabited planets. As it approaches a world and installs itself as a new moon, it causes an escalating Zombie Apocalypse.
- Stars infested by the power of the Far Realms dance and waver across the sky at will, driven by a malign intelligence. They're also prone to reach out to mortal minds, offering them pacts to become Warlocks. Allabar, the "Opener of the Way," is an intelligent, malevolent planet covered in eyes and tentacles that moves through the cosmos towards those hostile stars, helping their star spawn descend to the world of mortals.
- Numenera: Xeobrenicus is a planet that drifts through interstellar space, and consequently lacks any external source of light and energy. Instead, it's permeated with large stores of a unique radioactive mineral, which provides the energy to keep its global ocean from freezing and serves as the basis of its biosphere while also making it too irradiated for offworld life to survive on its surface.
- Transformers: Cybertron wanders through space without an orbit, which is why the characters tend to rely on a teleportation device to make it back and forth. Similarly, Unicron's vehicle mode, itself a planet, flies through space of its own volition.
- Metroid Prime 2: Echoes: Aether is a rogue planet that does not orbit a star. Instead, light and heat are provided to its surface inhabitants by a mysterious native energy referred to as "the Light of Aether".
- Star Control 3: The Owa are one of very few alien races in the franchise whose homeworld can't simply be happened across as you're exploring. That's because your ship's navigation is based on travel from star system to star system, and the Owa inhabit a rogue planet. You can't travel there without coordinates straight from the Owa themselves.
- In The Journeyman Project 2: Buried in Time, one of the alien races in the Symbiotry of Peaceful Beings, the Lôxôni, live on a rogue planet constantly pulled apart by gravity from different solar systems. They make use of this by utilizing the resultant cracks and fissures as living space and resources.
- AI War: Fleet Command: Nomad Planets wander all over the galaxy with seemingly random pace and direction. Normally this wouldn't matter thanks to interplanetary travel using fixed wormholes, but these planets also generate unstable wormholes in nearby locations, thus generating entirely new, if temporary routes around the place. Up to ten can be found in a galaxy at a given time.
- Dad has an entire song named after real-life rogue planet CFBDSIR_2149-0403. Dad discusses that something went down there, but what is never revealed, because not even he knows.
- Gemini Home Entertainment's main antagonist, The Iris, is a sentient rogue planet that's in the process of launching a full-scale attack on the Solar System. Worse still, it knows that life exists on Earth, and it's coming for us.
THE STARS ARE MOVING NOWDO YOU SEE THE HUNGRY EYE
- Kurzgesagt's video about What If Earth got Kicked Out of the Solar System? deals with how a rogue star entering our solar system could cause a mass extinction on Earth as we saw with the dinosaurs. It could also push Earth out of its orbit and turn it into a freezing rogue planet with no higher life left on its surface.
- Truth in Television. Though they're understandably difficult to detect, a handful of these planets have been discovered over the years and it's believed there may be billions out there. Most are believed to have originated in a solar system before being ejected by a close encounter with another massive object. Hopefully they weren't inhabited at the time.
- ʻOumuamua was the first interstellar visitor we discovered in our solar system, but our measurements of it are notoriously spotty; by the time we noticed it, it was already on its way back out of the solar system, and at such a speed that it is beyond our reach to send up probes. Thus these spotty measurements are all we have, and while the general consensus is that it is too small to be a planet, it cannot be ruled out entirely.note