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"[1] 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."[2]). 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 cleaning up the naming business in the late 1970s.
Prehistory |
Name |
Image |
Other designation |
Notes |
Sun |
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Star |
In Ptolemy's geocentric model, 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 no longer considered to be planets; it also excluded the Earth. |
Moon |
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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. |
Mercury |
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1st Planet |
The inner planets, Mercury and Venus, and the outer planets, Mars, Jupiter and Saturn, were identified by ancient Babylonian astronomers in the 2nd millennium BC.[3]
By Aristarchus of Samos, and later 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.
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Venus |
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2nd Planet |
Earth |
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3rd Planet |
Mars |
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4th Planet |
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