Timeline of discovery of Solar System planets and their moons
This timeline of discovery of Solar System planets and their natural satellites charts the progress of the discovery of new bodies over history.
Historically the naming of natural satellites did not always match the times of their discovery.
In the following tables, planetary satellites are indicated in bold type (e.g. Moon) while planets, major or minor, which directly circle the Sun are in italic type (e.g. Earth). 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 (the true "discovery" moment);
- p: for date of announcement or publication.
*Note: Marked moons had complicated discoveries. Several moons took several years to be confirmed, and in several cases were actually lost and rediscovered. Others were found in Voyager photographs years after they were taken.
Color code
The planets and their natural satellites are marked in the following colors:
Mercury | Venus | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Earth and satellite | Mars and satellites | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Jupiter and satellites | Saturn and satellites | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Uranus and satellites | Neptune and satellites | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Dwarf planets | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Pluto and satellites | 2003 UB313 and satellites |
Prehistory
Prehistory | |||||
---|---|---|---|---|---|
Date | Name | Designation | Image | Planet/Number Designation | References/Notes |
Unknown | Sun | ![]() |
Star | In the Ptolemaic system, 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, first 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 no longer considered to be planets; it also excluded the Earth. | |
Unknown | Mercury | ![]() |
Planet | In Nicolaus Copernicus' heliocentric system (De Revolutionibus Orbium Coelestium, 1543) the Earth came to be considered a planet revolving with the other planets around the Sun, in the following order of distance from the Sun: Mercury, Venus, Earth, Mars, Jupiter, and Saturn. The Sun, now situated near the center of revolution, was no longer considered a planet. | |
Venus | Planet | ||||
Earth | ![]() |
Planet | |||
Mars | ![]() |
Planet | |||
Jupiter | ![]() |
Planet | |||
Saturn | ![]() |
Planet | |||
Unknown | Moon | ![]() |
Earth I | In the Copernican system, the Moon was considered to be no longer a planet but a natural satellite of the Earth, and was the only body in that system whose revolution was not centered on the Sun. |
17th century
17th century | |||||
---|---|---|---|---|---|
Date | Name | Designation | Image | Planet/Number Designation | References/Notes |
1610s | |||||
o: January 7 1610 p: March 13 1610 |
Callisto | ![]() |
Jupiter IV | Galileo, Sidereus Nuncius, [1]. The Galilean moons. Note: One of the moons may have been recorded by the Chinese astronomer Gan De in 364 BC. The Galilean satellites were the first celestial objects that were confirmed to orbit an object other than the Earth. | |
Io | ![]() |
Jupiter I | |||
Europa | ![]() |
Jupiter II | |||
o: January 11 1610 p: March 13 1610 |
Ganymede | ![]() |
Jupiter III | ||
1650s | |||||
o: March 25 1655 p: March 5 1656 |
Titan | ![]() |
Saturn VI | Huygens, [2]. Huygens first "published" his discovery as an anagram, sent out on June 13, 1655; later published in pamphlet form as De Saturni luna Observatio Nova and in full in Systema Saturnium (July 1659). | |
1670s | |||||
o: October 25 1671 p: 1673 |
Iapetus | ![]() |
Saturn VIII | Cassini, [3]. Cassini published these two discoveries in Découverte de deux nouvelles planètes autour de Saturne (Sébastien Mabre-Cramoisy, Paris, 1673), translated as A Discovery of Two New Planets about Saturn, Made in the Royal Parisian Observatory by Signor Cassini, Philosophical Transactions 8 (1673), pp. 5178-5185. There may just be earlier publications within the Journal des scavans. | |
o: December 23, 1672 | Rhea | ![]() |
Saturn V | ||
1680s | |||||
o: March 21, 1684 | Tethys | ![]() |
Saturn III | Cassini. Cassini published these two discoveries on April 22, 1686, judging by An Extract of the Journal Des Scavans of April 22 st. N. 1686, Giving an Account of Two New Satellites of Saturn, Discovered Lately by Mr. Cassini at the Royal Observatory at Paris, Philosophical Transactions 16 (1686-1692) pp. 79-85. 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 | Designation | Image | Planet/Number Designation | References/Notes |
18th century
18th century | |||||
---|---|---|---|---|---|
Date | Name | Designation | Image | Planet/Number Designation | References/Notes |
1780s | |||||
o: March 13 1781 p: April 26 1781 |
Uranus | ![]() |
Planet | Herschel [4]. Herschel first reported the discovery of Uranus on April 26, 1781, hedging by calling it a "comet": Account of a Comet, By Mr. Herschel, F. R. S.; Communicated by Dr. Watson, Jun. of Bath, F. R. S., Philosophical Transactions of the Royal Society of London, Volume 71, pp. 492-501. | |
o: January 11 1787 | Titania | ![]() |
Uranus III | Herschel | |
Oberon | ![]() |
Uranus IV | Herschel | ||
o: August 28 1789 | Enceladus | ![]() |
Saturn II | Herschel | |
o: September 17 1789 | Mimas | ![]() |
Saturn I | Herschel [5] | |
Date | Name | Designation | Image | Planet/Number Designation | References/Notes |
19th century
19th century | |||||
---|---|---|---|---|---|
Date | Name | Designation | Image | Planet/Number Designation | References/Notes |
1800s | |||||
o: January 1, 1801 | 1 Ceres | ![]() |
Dwarf planet | Giuseppe Piazzi | |
1840s | |||||
o: September 23, 1846 | Neptune | ![]() |
Planet | Galle and Le Verrier [6] | |
o: October 10, 1846 | Triton | ![]() |
Neptune I | Lassell [7] [8] | |
o: September 16, 1848 | Hyperion | ![]() |
Saturn VII | Bond, Bond, Lassell [9] [10] | |
1850s | |||||
o: October 24, 1851 | Ariel | ![]() |
Uranus I | Lassell [11] | |
Umbriel | ![]() |
Uranus II | Lassell [12] | ||
1870s | |||||
o: August 12, 1877 | Deimos | ![]() |
Mars II | Hall [13] [14] [15] | |
o: August 18, 1877 | Phobos | ![]() |
Mars I | Hall [16] [17] [18] | |
1890s | |||||
o: September 9, 1892 p: October 4 1892 |
Amalthea | ![]() |
Jupiter V | Barnard [19] | |
i: August 16, 1898 o: March 17 1899 |
Phoebe | ![]() |
Saturn IX | Pickering [20] [21] | |
Date | Name | Designation | Image | Planet/Number Designation | References/Notes |
20th century
21st century
External links
- City of Hudson's Natural Satellite Page
- Gazetteer of Planetary Nomenclature
- Scott Sheppard's Giant Planet Satellite Page
- JPL Natural Satellite Discovery Data
- When Did the asteroids Become Minor Planets?