Planets outside of the Solar System have appeared in fiction since at least the 1850s, long before the first real ones were discovered in the 1990s. Most of these fictional planets do not differ signi
Artist's impression of a planet in a far-off system
Artist's impression of a chlorine planet
Various unknown astronomical objects have been hypothesized throughout recorded history. For example, in the 5th century BCE, the philosopher Philolaus defined a hypothetical astronomical object which
Extrasolar planets in fiction
…both tidal waves the height of mountains and extreme time dilation. Other fictional planets differ in their chemical rather than physical environment. Chlorine planets appear in Isaac Asimov's 1951 short story "C-Chute" and the 1976 Space: 1999 episode "The AB Chrysalis", while C. J. Cherryh's 1988 novel Cyteen depicts…
Artist's concept of Earth, orbited by a hypothetical second moon
Artist's concept of a carbon planet. The surface is dark and reddish from hydrocarbon deposits.