Various unknown

astronomical object An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists within the observable universe. In astronomy, the terms ''object'' and ''body'' are of ...

s have been hypothesized throughout

recorded history Recorded history or written history describes the historical events that have been recorded in a written form or other documented communication which are subsequently evaluated by historians using the historical method. For broader world h ...

. For example, in the 5th century BCE, the philosopher

Philolaus Philolaus (; , ''Philólaos''; ) was a Greek Pythagorean and pre-Socratic philosopher. He was born in a Greek colony in Italy and migrated to Greece. Philolaus has been called one of three most prominent figures in the Pythagorean tradition and ...

defined a hypothetical astronomical object which he called the " Central Fire", around which he proposed other celestial bodies (including the Sun) moved.Marco Ceccarelli, ''Distinguished Figures in Mechanism and Machine Science'' (2007), p. 124.

Types of hypothetical astronomical objects

Hypothetical astronomical objects have been speculated to exist both inside and outside of the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

, and speculation has included different kinds of stars, planets, and other astronomical objects. * For hypothetical astronomical objects in the Solar System, see:

List of hypothetical Solar System objects A hypothetical Solar System object is a planet, natural satellite, subsatellite or similar body in the Solar System whose existence is not known, but has been inferred from observational scientific evidence. Over the years a number of hypothetic ...

* For hypothetical stars, see:

Hypothetical star A hypothetical star is a star, or type of star, that is speculated to exist but has yet to be definitively observed. Hypothetical types of stars have been conjectured to exist, have existed or will exist in the future universe. Types Scientifica ...

* For hypothetical

brown dwarf Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main sequence, main-sequence stars. Their mass is approximately 13 to 80 Jupiter mass, times that of Jupiter ()not big en ...

s, see:

List of brown dwarfs A list is a set of discrete items of information collected and set forth in some format for utility, entertainment, or other purposes. A list may be memorialized in any number of ways, including existing only in the mind of the list-maker, bu ...

* For hypothetical black holes, see: Hypothetical black hole * For extrasolar moons, all of which are currently hypothetical, see: Extrasolar moon * For stars, planets or moons whose existence is not accepted by science, see:

Planetary objects proposed in religion, astrology, ufology and pseudoscience There are a number of planetary objects proposed in religion, astrology, ufology and pseudoscience whose existence is not supported by scientific evidence. Kolob Kolob is a star or planet described in the Book of Abraham, a sacred text in man ...

and

Stars proposed in religion Stars proposed in religion may include: * Kolob, a star proposed in Mormon cosmology * The Star of Bethlehem, the star that supposedly marked the birth of Christ * Wormwood (Bible), a star said to fall to Earth in the Book of Revelation * Seven S ...

* For hypothetical planets in fiction, see:

Fictional planets of the Solar System Fictional planets of the Solar System have been depicted since the 1700s—often but not always corresponding to List of hypothetical Solar System objects, hypothetical planets that have at one point or another been seriously proposed by real-wor ...

Hypothetical planet types

Hypothetical types of extrasolar planets include: , - ,

Ocean planet An ocean world, ocean planet or water world is a type of planet or natural satellite that contains a substantial amount of water in the form of oceans, as part of its hydrosphere, either beneath the planetary surface, surface, as subsurface ...

, , A planet whose surface is covered entirely by deep oceans. , - ,

Superhabitable planet A superhabitable world is a hypothetical type of planet or moon that is better suited than Earth for the emergence and evolution of life. The concept was introduced in a 2014 paper by René Heller and John Armstrong, in which they criticized the ...

, , A terrestrial planet that is more

habitable Habitability is the adequacy of an environment for human living. Where housing is concerned, there are generally local ordinances which define habitability. If a residence complies with those laws, it is said to be habitable. In extreme environ ...

than Earth. , - ,

Tidally detached exomoon Tidally detached exomoons, also known as orphaned exomoons or ploonets, are hypothetical exoplanets that were formerly exomoons of another planet, before being ejected from their orbits around their parent planets by tidal forces during planetary m ...

, , A planet that was originally a moon but has become gravitationally detached. , - ,

Toroidal planet A toroidal planet is a hypothetical type of terrestrial planet, telluric exoplanet with a Torus, toroidal or doughnut shape. While no firm theoretical understanding as to how toroidal planets could Planetary formation, form naturally is necessari ...

, , A planet whose shape resembles a

torus In geometry, a torus (: tori or toruses) is a surface of revolution generated by revolving a circle in three-dimensional space one full revolution about an axis that is coplanarity, coplanar with the circle. The main types of toruses inclu ...

or doughnut. , - , Trojan planet , , A planet that orbits near the or

Lagrange points In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium for small-mass objects under the gravitational influence of two massive orbiting bodies. Mathematically, this involves t ...

of a more massive object.

References

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