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 stated he would "defer any suggestions as to a name" [for 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 [Lysithea and Carme] are 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. 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 the discovery observation. This is not always the date of first imaging (photography, etc.) – see precovery; o: for date of first human visual observation, either through telescope 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 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 the ones agreed on by most astronomers, corresponding to a threshold of about 900–1000 km diameter. There may be more; some of the largest objects beyond that threshold are included in the fourth column as candidates. 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 <onlyinclude> Prehistory Name Image Other designation Notes Sun Star In the geocentric model, developed in Ancient Greece, then standardized by Ptolemy in the 2nd century, the Earth was believed to be at the center of the cosmos. Seven planets were placed in orbit around it in an order of increasing distance from the Earth, as established by the Greek Stoics: the Moon, Mercury, Venus, the Sun, Mars, Jupiter, and Saturn. This list included two objects, the Sun and the Moon, which are now not generally considered planets. In the 5th century BCE, the Greek philosophers Philolaus and Hicetas speculated separately that the Earth was a sphere revolving daily around some mystical "central fire" that regulated the universe. Anaxagoras proposed that the Sun is a star around 450 BCE. In the 3rd century BCE, Aristarchus of Samos extended this idea by proposing that the Earth and other planets moved around a definite central object, which he believed to be the Sun, although this was not widely accepted until the 17th century and not proven until the 19th. Earth 3rd PlanetEarth is the third planet from the Sun and the subject of historical misconception for centuries. Earth was never formally 'discovered' because it was never an unrecognized entity by humans. However, its shared identity with other bodies as a "planet" is a historically recent discovery.

The Earth's position in the Solar System was correctly described in the heliocentric model proposed by Aristarchus of Samos, but not widely recognized until the Copernican Revolution. Moon Earth I Prior to the Copernican Revolution, the moon was considered one of the seven classical planets, and its geologic features were one of the discoveries that convinced astronomers that the earth was in fact a planet like the moon. In the Copernican system, the Moon was considered a secondary planet (ie, natural satellite of the Earth), and was originally thought to be the only body in that system whose revolution was not centered on the Sun. Mercury 1st Planet Mercury, Venus, Mars, Jupiter and Saturn were identified by ancient Babylonian astronomers in the 2nd millennium BCE. They were correctly identified as orbiting the Sun by Aristarchus of Samos, and later in Nicolaus Copernicus' heliocentric system (De revolutionibus orbium coelestium, 1543) Venus2nd Planet Mars 4th Planet|}</onlyinclude> Jupiter 5th Planet Saturn 6th Planet

17th century 17th century Date Name Image Permanent designation Discoverer(s) and notes 1610s o: 7 January 1610p: 13 March 1610 Ganymede Jupiter III GalileoGalilei, Galileo; Sidereus Nuncius , Thomam Baglionum (Tommaso Baglioni), Venice (March 1610), pp. 17–28 (q.v.) discovered the Galilean moons of Jupiter. These satellites were the first celestial objects that were confirmed to orbit an object other than the Sun or Earth. Galileo saw Io and Europa as a single point of light on 7 January 1610; they were seen as separate bodies the following night. Callisto Jupiter IV o: 8 January 1610p: 13 March 1610 Io Jupiter I Europa Jupiter II 1650s o: 25 March 1655p: 5 March 1656 Titan Saturn VI, Huygens first "published" his discovery as an anagram, sent out on 13 June 1655; later published in pamphlet form as De Saturni luna Observatio Nova and in full in Systema Saturnium (July 1659). 1670s o: 25 October 1671p: 1673 Iapetus Saturn VIII, , CassiniCassini, Giovanni D.; Découverte de deux nouvelles planètes autour de Saturne , Sébastien Mabre-Cramoisy, Paris, 1673.Translated as o: 23 December 1672p: 1673 Rhea Saturn V, 1680s o: 21 March 1684p: 22 April 1686 Tethys Saturn III Cassini Together with his previous two discoveries, Cassini named these satellites Sidera Lodoicea. In his work Kosmotheôros (published posthumously in 1698), Christiaan Huygens relates "Jupiter you see has his four, and Saturn his five Moons about him, all plac’d in their Orbits." Dione Saturn IV Date Name Image Permanent designation Discoverer(s) and notes

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 18th century Date Name Image Other/Permanent designation Discoverer(s) and notes 1780s o: 13 March 1781p: 26 April 1781 Uranus 7th Planet Herschel first reported the discovery of Uranus on 26 April 1781, initially believing it to be a comet.o: 11 January 1787p: 15 February 1787 Titania Uranus III Herschel.Herschel, William; On George's Planet and its satellites, Philosophical Transactions of the Royal Society of London, Vol. 78, pp. 364–378, 1788 He later reported four more spurious satellites.Herschel, William; On the Discovery of Four Additional Satellites of the Georgium Sidus. The Retrograde Motion of Its Old Satellites Announced; And the Cause of Their Disappearance at Certain Distances from the Planet Explained, Philosophical Transactions of the Royal Society of London, Vol. 88, pp. 47–79, 1798 Oberon Uranus IVo: 28 August 1789p: 12 November 1789 Enceladus Saturn II Herschel o: 17 September 1789p: 12 November 1789 Mimas Saturn I Date Name Image Other/Permanent designation Discoverer(s) and notes

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 19th century Date Name Image Other/Permanent designation Discoverer(s) and notes 1800s o: 1 January 1801p: 24 January 1801 Ceres 8th Planet (1801)Asteroid (1851)Dwarf planet (2006) Giuseppe Piazzi. He first announced his discovery on 24 January 1801, in letters to fellow astronomers. The first formal publication was the September 1801 issue of the Monatliche Correspondenz. 1840s o: 23 September 1846p: 13 November 1846 Neptune 13th Planet (1846)8th Planet (1851) Galle and Le Verrier o: 10 October 1846p: 13 November 1846 Triton Neptune I Lassell o: 16 September 1848p: 7 October 1848 Hyperion Saturn VII Bond, Bond, Lassell 1850s o: 24 October 1851 Ariel Uranus I LassellLassell, W.; Letter from William Lassell, Esq., to the Editor, Astronomical Journal, Vol. 2, No. 33 (1851), p. 70 (signed 11 November 1851) Umbriel Uranus II 1870s o: 12 August 1877 Deimos Mars II HallChristie, William H. M.; The Satellites of Mars, The Observatory, Vol. 1, No. 6 (20 September 1877), pp. 181–185Hall, Asaph; Observations of the Satellites of Mars (signed 21 September 1877), Astronomische Nachrichten, Vol. 91, No. 2161 (17 October 1877), pp. 11/12–13/14Hall, Asaph; The Discovery of the Satellites of Mars (signed 28 December 1877), Monthly Notices of the Royal Astronomical Society, Vol. 38, No. 4 (8 February 1878), pp. 205–209 o: 18 August 1877 Phobos Mars I 1890s o: 9 September 1892p: 4 October 1892 Amalthea Jupiter V Barnard i: 16 August 1898o: 17 March 1899 Phoebe Saturn IX PickeringPickering, Edward C.; A New Satellite of Saturn, Harvard College Observatory Bulletin, No. 49 (17 March 1899), p. 1Pickering, Edward C.; A New Satellite of Saturn (signed 10 April 1899), Astrophysical Journal, Vol. 9, No. 4 (April 1899), pp. 274–276 Date Name Image Other/Permanent designation Discoverer(s) and notes

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 Early 20th century Date Name Image Permanent designation Discoverer(s) and notes 1900s i: 3 December 1904p: 6 January 1905 Himalia Jupiter VI PerrineCampbell, William W.; Sixth Satellite of Jupiter, Harvard College Observatory Bulletin, No. 173 (6 January 1905), p. 1 Perrine, Charles D.; Discovery of a Sixth Satellite to Jupiter (signed 30 January 1905), Publications of the Astronomical Society of the Pacific, Vol. 17, No. 100 (10 February 1905), pp. 22–23