Timeline of discovery of Solar System planets and their moons

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:

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.