Timeline of discovery of solar system planets and their natural satellites
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The timeline of discovery of Solar System planets and their natural satellites 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 Edward Emerson Barnard (December 16, 1857 – February 6, 1923) was an American astronomer. He was commonly known as E. E. Barnard, and was recognized as a gifted observational astronomer. He is best known for his discovery of the high proper mo ...
stated he would "defer any suggestions as to a name"
or Amalthea Or or OR may refer to: Arts and entertainment Film and television * "O.R.", a 1974 episode of M*A*S*H * Or (My Treasure), a 2004 movie from Israel (''Or'' means "light" in Hebrew) Music * ''Or'' (album), a 2002 album by Golden Boy with Mis ...
"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 (IAU) eventually started officially approving names in the late 1970s.


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 or on
photographic plate Photographic plates preceded photographic film as a capture medium in photography, and were still used in some communities up until the late 20th century. The light-sensitive emulsion of silver salts was coated on a glass plate, typically thinn ...
; * ''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. Some took years to be confirmed, and in several cases were actually lost and rediscovered. Others were found in
Voyager Voyager may refer to: Computing and communications * LG Voyager, a mobile phone model manufactured by LG Electronics * NCR Voyager, a computer platform produced by NCR Corporation * Voyager (computer worm), a computer worm affecting Oracle ...
photographs years after they were taken.'' ;Color legend The Sun, the planets, dwarf planets, and their natural satellites are marked in the following colors: ;Sun ;Planets ;Consensus dwarf planets ;Other dwarf planet candidates It is not known precisely how many objects in the Solar System are dwarf planets; the nine objects listed in the third column are those agreed on by most astronomers, corresponding to a threshold of about 900 km diameter. There may be more; here, all objects with estimated diameter over 700 km are included as dwarf planet candidates, listed in the fourth column. In particular, Salacia and Varda each have a rather large moon, and current estimates for their densities still leave open the possibility that they are dwarf planets. ;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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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 nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...
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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 sometimes adopted Herschel's numbers where Titania and Oberon are respectively Uranus II and IV, 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 So ...
* Solar System


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 James Lindsay Hilton (born February 21, 1957) has been an astronomer at the United States Naval Observatory since 1986. In 1999 he published a new set of ephemerides for 15 of the largest asteroids for use in the Astronomical Almanac. Education Hi ...

When did the asteroids become minor planets?
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