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The timeline of discovery of Solar System
planet A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...
s and their
natural satellite A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are colloquially referred to as moons, a deriv ...
s charts the progress of the discovery of new bodies over history. Each object is listed in chronological order of its discovery (multiple dates occur when the moments of imaging, observation, and publication differ), identified through its various designations (including temporary and permanent schemes), and the discoverer(s) listed. Historically the naming of moons did not always match the times of their discovery. Traditionally, the discoverer enjoys the privilege of naming the new object; however, some neglected to do so ( E. E. Barnard stated he would "defer any suggestions as to a name" or Amalthea"until a later paper" but never got around to picking one from the numerous suggestions he received) or actively declined ( S. B. Nicholson stated "Many have asked what the new satellites ysithea and Carmeare to be named. They will be known only by the numbers X and XI, written in Roman numerals, and usually prefixed by the letter J to identify them with Jupiter."). The issue arose nearly as soon as planetary satellites were discovered: Galileo referred to the four main satellites of Jupiter using numbers while the names suggested by his rival Simon Marius gradually gained universal acceptance. The
International Astronomical Union The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...
(IAU) eventually started officially approving names in the late 1970s. With the explosion of discoveries in the 21st century, new moons have once again started to be left unnamed even after their numbering, beginning with Jupiter LI and Jupiter LII in 2010.


Key info

In the following tables, planetary satellites are indicated in bold type (e.g. Moon) while planets and dwarf planets, which directly circle the Sun, are in italic type (e.g. ''Earth''). The Sun itself is indicated in roman type. The tables are sorted by publication/announcement date. Dates are annotated with the following symbols: * ''i:'' for date of first imaging (photography, etc.); * ''o:'' for date of first human visual observation, either through
telescope A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...
or on photographic plate; * ''p:'' for date of announcement or publication. In a few cases, the date is uncertain and is then marked "(?)". ''* Note: Moons marked by an asterisk (*) had complicated discoveries, such as being lost and rediscovered. Some of them thus appear multiple times in the list to clarify the situation.'' ;Color legend The Sun, the
planet A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...
s,
dwarf planet A dwarf planet is a small planetary-mass object that is in direct orbit around the Sun, massive enough to be hydrostatic equilibrium, gravitationally rounded, but insufficient to achieve clearing the neighbourhood, orbital dominance like the ...
s, and their natural satellites are marked in the following colors: ;Sun ;Planets ;Consensus dwarf planets It is not known precisely how many objects in the Solar System are dwarf planets. The nine objects listed in the third column are the ones agreed on by most astronomers, corresponding to a threshold of about 900–1000 km diameter. ;Designations * Other designations are synonyms or periphrases sometimes encountered for the object. * Permanent designations (of planetary satellites) are explained here. * Temporary designations are explained here. If a satellite is named, its name is bolded; if it is unnamed, but has a permanent designation, then its permanent designation is bolded; and if it has neither, then its temporary designation is bolded.


Prehistorically discovered

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Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
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Saturn Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...
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17th century

The numbering of Saturn's moons was adjusted with each new discovery until 1848, in order to continue reflecting their order from their parent planet.


18th century

The numbering of Titania and Oberon underwent some confusion, because in 1797, Herschel reported four more satellites of Uranus that turned out not to exist. Before any more Uranian moons were discovered,
William Lassell William Lassell (18 June 1799 – 5 October 1880) was an English merchant and astronomer. and sometimes called them respectively Uranus I and II. After he discovered Ariel and Umbriel in 1851, Lassell numbered the four real Uranian satellites then known outward from their parent planet as I (Ariel), II (Umbriel), III (Titania), and IV (Oberon), and this finally stuck.


19th century

The discovery of Amalthea marks the first time the Roman numerals were not adjusted with the discovery of a new satellite; from then on they reflected order of discovery rather than distance from the parent planet.


20th century


1901–1950


1951–2000


21st century


2000s


2010s


2020s


See also

* Timeline of Solar System astronomy * Timeline of Solar System exploration *
Lists of astronomical objects This is a list of lists, grouped by type of astronomical object. Solar System * List of Solar System objects * List of gravitationally rounded objects of the Solar System * List of Solar System objects most distant from the Sun * List of ...
*
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 ...


References


External links


City of Hudson's Natural Satellite Page

Scott Sheppard's Giant Planet Satellite Page

JPL Natural Satellite Discovery Data
* James L. Hilton
When did the asteroids become minor planets?
{{Portal bar, Lists, Stars, Spaceflight, Outer space, Science Moons Discovery and exploration of the Solar System Lists of Solar System objects Solar system, planets, natural satellites, timeline of Solar system objects Solar System