In the Solar System, a planet is said to be inferior or interior with respect to another planet if its orbit lies inside the other planet's orbit around the Sun. In this situation, the latter planet is said to be superior to the former. In the reference frame of the Earth, in which the terms were originally used, the inferior planets are Mercury and Venus, while the superior planets are Mars, Jupiter, Saturn, Uranus and Neptune. Dwarf planets like Ceres or Pluto and most asteroids are 'superior' in the sense that they almost all orbit outside the orbit of Earth.
History
These terms were originally used in the geocentric cosmology of Claudius Ptolemy to differentiate as inferior those planets (Mercury and Venus) whose epicycle remained co-linear with the Earth and Sun, and as superior those planets (Mars, Jupiter, and Saturn) that did not.[1]
In the 16th century, the terms were modified by Copernicus, who rejected Ptolemy's geocentric model, to distinguish a planet's orbit's size in relation to the Earth's.[2]
Planets in each category
When Earth is stated or assumed to be the reference point:
"Inferior planet" refers to Mercury and Venus, which are closer to the Sun than Earth is.
"Superior planet" refers to Mars, Jupiter, Saturn, Uranus, and Neptune (the latter two added later), which are farther from the Sun than Earth is.
The terms are sometimes used more generally; for example, Earth is an inferior planet relative to Mars.
Other planetary terms
Interior planet now seems to be the preferred term for astronomers. Inferior/interior and superior are different from the terms inner planet and outer planet, which designate those planets which lie inside the asteroid belt and those that lie outside it, respectively. Inferior planet is also different from minor planet or dwarf planet. Superior planet is also different from gas giant.
References
Lakatos, Imre; Worrall, John; Currie, Gregory (1980). Worrall, John; Currie, Gregory (eds.). The Methodology of Scientific Research Programmes. Cambridge University Press. p. 186. ISBN 0-521-28031-1.
Kuhn, Thomas S. (1985). The Copernican Revolution: Planetary Astronomy in the Development of Western Thought (4th ed.). Harvard University Press. p. 172. ISBN 0-674-17103-9.
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Ancient Greek astronomy
Astronomers
Aglaonice Agrippa Anaximander Andronicus Apollonius Aratus Aristarchus Aristyllus Attalus Autolycus Bion Callippus Cleomedes Cleostratus Conon Eratosthenes Euctemon Eudoxus Geminus Heraclides Hicetas Hipparchus Hippocrates of Chios Hypsicles Menelaus Meton Oenopides Philip of Opus Philolaus Posidonius Ptolemy Pytheas Seleucus Sosigenes of Alexandria Sosigenes the Peripatetic Strabo Thales Theodosius Theon of Alexandria Theon of Smyrna Timocharis
Works
Almagest (Ptolemy) On Sizes and Distances (Hipparchus) On the Sizes and Distances (Aristarchus) On the Heavens (Aristotle)
Instruments
Antikythera mechanism Armillary sphere Astrolabe Dioptra Equatorial ring Gnomon Mural instrument Triquetrum
Concepts
Callippic cycle Celestial spheres Circle of latitude Counter-Earth Deferent and epicycle Equant Geocentrism Heliocentrism Hipparchic cycle Metonic cycle Octaeteris Solstice Spherical Earth Sublunary sphere Zodiac
Influences
Babylonian astronomy Egyptian astronomy
Influenced
Medieval European science Indian astronomy Medieval Islamic astronomy
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Solar System
The Sun, the planets, their moons, and several trans-Neptunian objects
Sun Mercury Venus Earth Mars Ceres Jupiter Saturn Uranus Neptune Pluto Haumea Makemake Eris
Planets
Terrestrials
Mercury Venus Earth Mars Giants
Jupiter Saturn Uranus Neptune Dwarfs
Ceres Pluto Haumea Makemake Eris
Moons
Earth
Moon other near-Earth objects Mars
Phobos Deimos Jupiter
Ganymede Callisto Io Europa all 79 Saturn
Titan Rhea Iapetus Dione Tethys Enceladus Mimas Hyperion Phoebe all 82 Uranus
Titania Oberon Umbriel Ariel Miranda all 27 Neptune
Triton Proteus Nereid all 14 Pluto
Charon Nix Hydra Kerberos Styx Eris
Dysnomia Haumean
Hiʻiaka Namaka Makemake
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Lists
Comets Possible dwarf planets Gravitationally rounded objects Minor planets Natural satellites Solar System models Solar System objects
by size by discovery date Interstellar and circumstellar molecules
Small
Solar
System
bodies
Comets Damocloids Meteoroids Minor planets
names and meanings moons Planetesimal Mercury-crossers Venus-crossers Venus trojans Near-Earth objects Earth-crossers Earth trojans Mars-crossers Mars trojans Asteroid belt Asteroids
Ceres Pallas Juno Vesta active first 1000 families exceptional Kirkwood gap Jupiter-crossers Jupiter trojans Centaurs Saturn-crossers Uranus-crossers Uranus trojans Neptune-crossers Cis-Neptunian objects
Centaurs Neptune trojans Trans-Neptunian objects
Kuiper belt
Cubewanos Plutinos Detached objects Sednoids Scattered disc Oort cloud Hills cloud
Rings
Jovian Saturnian (Rhean) Charikloan Chironean Uranian Neptunian Haumean
Hypothetical
objects
Fifth giant Nemesis Phaeton Planet Nine Planet V Planet X Subsatellites Theia Tyche Vulcan Vulcanoids
Exploration
(outline)
Discovery
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Formation
and
evolution
Accretion Accretion disk
Excretion disk Circumplanetary disk Circumstellar disc Circumstellar envelope Coatlicue Cosmic dust Debris disk Detached Objects Disrupted planet EXCEDE Exozodiacal dust Extraterrestrial materials
Sample-return mission Sample curation Giant-impact hypothesis Gravitational collapse Hills Cloud Interplanetary dust cloud Interplanetary medium Interplanetary space Interstellar cloud Interstellar dust Interstellar medium Interstellar space Kuiper belt Merging stars Molecular cloud Nebular hypothesis Oort cloud Outer space Planetary migration Planetary system Planetesimal Planet formation Protoplanetary disk Ring system Rubble pile Scattered disc Star formation
Outline of the Solar System Solar system.jpg Solar System portal Crab Nebula.jpg Astronomy portal The Earth seen from Apollo 17 with transparent background.png Earth Sciences portal
Solar System → Local Interstellar Cloud → Local Bubble → Gould Belt → Orion Arm → Milky Way → Milky Way subgroup → Local Group → Local Sheet → Virgo Supercluster → Laniakea Supercluster → Observable universe → Universe
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