Provisional designation in astronomy

Provisional designation is the naming convention applied to astronomical objects immediately following their discovery. The provisional designation is usually superseded by a permanent designation once a reliable orbit has been calculated., approximately 47% of the more than 1,100,000 known minor planets remain provisionally designated, as hundreds of thousands have been discovered in the last two decades. The modern system is overseen by the Minor Planet Center of the International Astronomical Union.

Minor planets

The current system of provisional designation of minor planets has been in place since 1925. It superseded several previous conventions, each of which was in turn rendered obsolete by the increasing numbers of minor planet discoveries. A modern or new-style provisional designation consists of the year of discovery, followed by two letters and, possibly, a suffixed number.

New-style provisional designation

For example, the provisional designation stands for the 27th body identified during 16–31 Aug 1992:1992 – the first element indicates the year of discovery.Q – the first letter indicates the half-month of the object's discovery within that year and ranges from A to Y, while the letters I and Z are not used '. The first half is always the 1st through to the 15th of the month, regardless of the numbers of days in the second "half". Thus, Q indicates the period from Aug 16 to 31.B₁ – the second letter and a numerical suffix indicate the order of discovery within that half-month. The first 25 discoveries of the half-month only receive a letter without a suffix, while the letter I is not used. Because modern techniques typically yield hundreds if not thousands of discoveries per half-month, the subscript number is appended to indicate the number of times that the letters from A to Z have cycled through. The suffix 1 indicates one completed cycle, while B is the 2nd position in the current cycle. Thus, B₁ stands for the 27th minor planet discovered in a half-month.
The packed form of is written as.
This scheme is now also used retrospectively for pre-1925 discoveries. For these, the first digit of the year is replaced by an A. For example, A'''801 AA indicates the first object discovered in the first half of January 1801.

Further explanations

During the first half-month of January 2014, the first minor planet identification was assigned the provisional designation. Then the assignment continued to the end of the cycle at, which was in turn followed by the first identification of the second cycle,. The assignment in this second cycle continued with,,... until, and then was continued with the first item in the third cycle. With the beginning of a new half-month on 16 January 2014, the first letter changed to "B", and the series started with.
An idiosyncrasy of this system is that the second letter is listed before the number, even though the second letter is considered "least-significant". This is in contrast to most of the world's numbering systems. This idiosyncrasy is not seen, however, in the so-called packed form.
A packed designation has no spaces. It may also use letters to codify for the designation's year and subscript number. It is frequently used in online and electronic documents. For example, the provisional designation is written as K07Tf8A in the [|packed form], where "K07" stands for the year 2007, and "f8" for the subscript number 418.
90377 Sedna, a large trans-Neptunian object, had the provisional designation, meaning it was identified in the first half of November 2003, and that it was the 302nd object identified during that time, as 12 cycles of 25 letters give 300, and the letter "B" is the second position in the current cycle.
Survey designations do not follow the rules for new-style provisional designations.
For technical reasons, such as ASCII limitations, the numerical suffix is not always subscripted, but sometimes "flattened out", so that can also be written as.
A very busy half month was the second half of January 2015, which saw a total of 15,502 new minor planet identifications. One of the last assignments in this period was and corresponds to the 15,502nd position in the sequence.

Survey designations

Minor planets discovered during the Palomar–Leiden survey including three subsequent Trojan-campaigns, which altogether discovered more than 4,000 asteroids and Jupiter trojans between 1960 and 1977, have custom designations that consist of a number followed by a space and one of the following identifiers:P-L Palomar–Leiden survey T-1 Palomar–Leiden Trojan survey T-2 Palomar–Leiden Trojan survey T-3 Palomar–Leiden Trojan survey
For example, the asteroid 6344 P-L is the 6344th minor planet in the original Palomar–Leiden survey, while the asteroid 4835 T-1 was discovered during the first Trojan-campaign. The majority of these bodies have since been assigned a number and many are already named.

Historical designations

The first four minor planets were discovered in the early 19th century, after which there was a lengthy gap before the discovery of the fifth. Astronomers initially had no reason to believe that there would be countless thousands of minor planets, and strove to assign a symbol to each new discovery, in the tradition of the symbols used for the major planets. For example, 1 Ceres was assigned a stylized sickle, 2 Pallas a stylized lance or spear, 3 Juno a scepter, and 4 Vesta an altar with a sacred fire. All had various graphic forms, some of considerable complexity.
It soon became apparent, though, that continuing to assign symbols was impractical and provided no assistance when the number of known minor planets was in the dozens. Johann Franz Encke introduced a new system in the Berliner Astronomisches Jahrbuch for 1854, published in 1851, in which he used encircled numbers instead of symbols. Encke's system began the numbering with Astraea which was given the number and went through Eunomia, while Ceres, Pallas, Juno and Vesta continued to be denoted by symbols, but in the following year's BAJ, the numbering was changed so that Astraea was number.
The new system found popularity among astronomers, and since then, the final designation of a minor planet is a number indicating its order of discovery followed by a name. Even after the adoption of this system, though, several more minor planets received symbols, including 28 Bellona the morning star and lance of Mars's martial sister, 35 Leukothea an ancient lighthouse and 37 Fides a Latin cross. According to Webster's A Dictionary of the English Language, four more minor planets were also given symbols: 16 Psyche, 17 Thetis, 26 Proserpina, and 29 Amphitrite. However, there is no evidence that these symbols were ever used outside of their initial publication in the Astronomische Nachrichten.
134340 Pluto is an exception: it is a high-numbered minor planet that received a graphical symbol with significant astronomical use, because it was considered a major planet on its discovery, and did not receive a minor planet number until 2006.
Graphical symbols continue to be used for some minor planets, and assigned for some recently discovered larger ones, mostly by astrologers. Three centaurs – 2060 Chiron, 5145 Pholus, and 7066 Nessus – and the largest trans-Neptunian objects – 50000 Quaoar, 90377 Sedna, 90482 Orcus, 136108 Haumea, 136199 Eris, 136472 Makemake, and 225088 Gonggong – have relatively standard symbols among astrologers: the symbols for Haumea, Makemake, and Eris have even been occasionally used in astronomy. However, such symbols are generally not in use among astronomers.

Genesis of the current system

Several different notation and symbolic schemes were used during the latter half of the nineteenth century, but the present form first appeared in the journal Astronomische Nachrichten in 1892. New numbers were assigned by the AN on receipt of a discovery announcement, and a permanent designation was then assigned once an orbit had been calculated for the new object.
At first, the provisional designation consisted of the year of discovery followed by a letter indicating the sequence of the discovery, but omitting the letter I. Under this scheme, 333 Badenia was initially designated, 163 Erigone was, etc. In 1893, though, increasing numbers of discoveries forced the revision of the system to use double letters instead, in the sequence AA, AB... AZ, BA and so on. The sequence of double letters was not restarted each year, so that followed and so on. In 1916, the letters reached ZZ and, rather than starting a series of triple-letter designations, the double-letter series was restarted with.
Because a considerable amount of time could sometimes elapse between exposing the photographic plates of an astronomical survey and actually spotting a small Solar System object on them, or even between the actual discovery and the delivery of the message to the central authority, it became necessary to retrofit discoveries into the sequence — to this day, discoveries are still dated based on when the images were taken, and not on when a human realised they were looking at something new. In the double-letter scheme, this was not generally possible once designations had been assigned in a subsequent year. The scheme used to get around this problem was rather clumsy and used a designation consisting of the year and a lower-case letter in a manner similar to the old provisional-designation scheme for comets. For example,, 1917 b. In 1914 designations of the form year plus Greek letter were used in addition.

Temporary minor planet designations

Temporary designations are custom designations given by an observer or discovering observatory prior to the assignment of a provisional designation by the MPC. These intricate designations were used prior to the Digital Age, when communication was slow or even impossible. The listed temporary designations by observatory or observer use uppercase and lowercase letters, digits, numbers and years, as well Roman numerals and Greek letters.

Observatory	Temp. designation	Examples
Algiers Obs.	Alger `LETTER`	Alger A, Alger CM
Algiers Obs.	Alg `LETTER`	Alg A, Alg CM
Alma-Ata	Alma-Ata `number`	Alma-Ata Nr. 1
Alma-Ata	`year` A `number`	1952 A1, A1
Arequipa	Arequipa `letter`	Arequipa a
Arequipa	Areq `letter`	Areq a
Arequipa	Arequipa `number`	Arequipa 17
Arequipa	Areq `number`	Areq 17
Belgrade Obs.	`year` `letter`	1956 x, 1956 x
Belgrade Obs.	`letter`	x
Lowell Obs.	A `number`	A0, A7
Heidelberg Obs.	Wolf `number`	Wolf Nr. 18, Wolf 18
Heidelberg Obs.	Wolf `letter`	Wolf u
Heidelberg Obs.	Wolf `greek`	Wolf alpha
Heidelberg Obs.	Heid `number`	Heid 1, Heid 234
Johannesburg Obs.	`LETTER`	A, E
Johannesburg Obs.	G `number`	G 1, G 21
Johannesburg Obs.	T `number`	T 9, T 16
Kyoto-Kwasan	`number`	1, 6
Kyoto-Kwasan	`letter`	d
La Plata Obs.	`year` `ROM`	La Plata 1951 I, 1951 I
La Plata Obs.	`year` `LETTER`	La Plata 1950 G, 1950 G
Lick	`LETTER`	Asteroid B, B
Mount Wilson Obs.	`LETTER`	Asteroid A, A
Mount Wilson Obs.	`LETTER`	D
Purple Mountain Obs.	P.O. `number`	P.O. 32, P.O. 189
Purple Mountain Obs.	PO `number`	PO 32, PO 189
Crimean Astrophysical Obs.	N `number`	N1
Crimean Astrophysical Obs.	K `number`	K1, K3423
Simeiz Obs.	SIGMA K `number`	1942 SIGMA K1, SIGMA K1
Simeiz Obs.	SIG K `number`	1942 SIG K1, SIG K1
Simeiz Obs.	sigma `number`	sigma 1, sigma 229
Taunton Obs.	Taunton `digit`	Taunton 83
Tokyo-Mitaka	Tokyo `LETTER`	Tokyo B
Tokyo-Mitaka	Tokyo `letter`	Tokyo b
Tokyo-Mitaka	Tokyo `number`	Tokyo 20
Tokyo-Mitaka	Tokyo `year` `LETTER`	Tokyo 1954 D
Turku Obs.	T- `number`	T-1, T-774
Uccle Obs.	`letter`	p, p
Uccle Obs.	`letter` `number`	x2, x2
Uccle Obs.	U `number`	1945 U 12, U 12
Washington	`year` W `digit`	1917 W 15, 1923 W 21
Yerkes Obs.	Y.O. `number`	Y.O. 23
Yerkes Obs.	YO `number`	YO 23

Traces in the permanent name

In some cases the provisional designation may carry over into the permanent name. For example, the asteroid 572 Rebekka had had the provisional designation 1905 RB, and similarly with the subsequently numbered asteroids 573 Recha, 574 Reginhild, 575 Renate, 577 Rhea, 579 Sidonia and 580 Selene. This pattern appeared sporadically over the next few years' discoveries up to 769 Tatjana and occasionally later. In 2025 it appeared again when the IAU named the largest unnamed numbered trans-Neptunian objects 208996 Achlys, 55565 Aya, 90568 Goibniu, 307261 Máni, 145452 Ritona, 145451 Rumina, 55637 Uni and 78799 Xewioso.

Comets

The system used for comets was complex previous to 1995. Originally, the year was followed by a space and then a Roman numeral in most cases, but difficulties always arose when an object needed to be placed between previous discoveries. For example, after Comet 1881 III and Comet 1881 IV might be reported, an object discovered in between the discovery dates but reported much later could not be designated "Comet 1881 III". More commonly comets were known by the discoverer's name and the year. An alternate scheme also listed comets in order of time of perihelion passage, using lower-case letters; thus "Comet Faye" was both Comet 1881 I and Comet 1880c.
The system since 1995 is similar to the provisional designation of minor planets. For comets, the provisional designation consists of the year of discovery, a space, one letter indicating the half-month of discovery within that year, and finally a number, indicating the sequence of discovery within the half-month. Thus, the eighth [|comet] discovered in the second half of March 2006 would be given the provisional designation 2006 F8, whilst the tenth comet of late March would be 2006 F10.
If a comet splits, its segments are given the same provisional designation with a suffixed letter A, B, C,..., Z, AA, AB, AC...
If an object is originally found asteroidal, and later develops a cometary tail, it retains its asteroidal designation. For example, minor planet 1954 PC turned out to be Comet Faye, and we thus have "4P/1954 PC" as one of the designations of said comet. Similarly, minor planet was reclassified as a comet, and because it was discovered by LINEAR, it is now known as 176P/LINEAR and (118401) LINEAR.
Provisional designations for comets are given condensed or "packed form" in the same manner as minor planets. 2006 F8, if a periodic comet, would be listed in the IAU Minor Planet Database as PK06F080. The last character is purposely a zero, as that allows comet and minor planet designations not to overlap.

Periodic comets

Comets are assigned one of four possible prefixes as a rough classification. The prefix "P" designates a "periodic comet", one which has an orbital period of less than 200 years or which has been observed during more than a single perihelion passage. They receive a permanent number prefix after their second observed perihelion passage .

Non-periodic comets

Comets which do not fulfill the "periodic" requirements receive the "C" prefix. Comets initially labeled as "non-periodic" may, however, switch to "P" if they later fulfill the requirements.
Comets which have been lost or have disintegrated are prefixed "D".
Finally, comets for which no reliable orbit could be calculated, but are known from historical records, are prefixed "X" as in, for example, X/1106 C1. ''''

Satellites and rings of planets

When satellites or rings are first discovered, they are given provisional designations such as "", "", or "". The initial "S/" or "R/" stands for "satellite" or "ring", respectively, distinguishing the designation from the prefixes "C/", "D/", "P/", and "X/" used for comets. These designations are sometimes written as "", dropping the second space.
The prefix "S/" indicates a natural satellite, and is followed by a year. A one-letter code written in upper case identifies the planet such as J and S for Jupiter and Saturn, respectively ', and then a number identifies sequentially the observation. For example, Naiad, the innermost moon of Neptune, was at first designated "". Later, once its existence and orbit were confirmed, it received its full designation, "".
The Roman numbering system arose with the very first discovery of natural satellites other than Earth's Moon: Galileo referred to the Galilean moons as I' through IV, in part to spite his rival Simon Marius, who had proposed the names now adopted. Similar numbering schemes naturally arose with the discovery of moons around Saturn and Uranus. Although the numbers initially designated the moons in orbital sequence, new discoveries soon failed to conform with this scheme. The unstated convention then became, at the close of the 19th century, that the numbers more or less reflected the order of discovery, except for prior historical exceptions ''. The convention has been extended to natural satellites of minor planets, such as "".

Moons of minor planets

Most minor-planet moons do not receive a provisional designation; they remain undesignated, like the moon of 38628 Huya. Provisional designations are only given when there are observations showing the satellite as a distinct entity separate from the primary. In those cases, the provisional designation system follows that established for the satellites of the major planets. With minor planets, the planet letter code is replaced by the minor planet number in parentheses. Thus, the first observed moon of 87 Sylvia, discovered in 2001, was at first designated S/2001 1, later receiving its permanent designation of Sylvia I Romulus. Where more than one moon has been discovered, Roman numerals specify the discovery sequence, so that Sylvia's second moon is designated Sylvia II Remus.
Since Pluto was reclassified in 2006, discoveries of Plutonian moons since then follow the minor-planet system: thus Nix and Hydra, discovered in 2005, were S/2005 P 2 and S/2005 P 1, but Kerberos and Styx, discovered in 2011 and 2012 respectively, were S/2011 1 and S/2012 1. That said, there has been some unofficial use of the formats "S/2011 P 1" and "S/2012 P 1".

Packed designation

Packed designations are used in online and electronic documents as well as databases.

Packed minor planet designation

The Orbit Database of the Minor Planet Center uses the "packed form" to refer to all provisionally designated minor planets. The idiosyncrasy found in the new-style provisional designations no longer exists in this packed-notation system, as the second letter is now listed after the subscript number, or its equivalent 2-digit code. For an introduction on provisional minor planet designations in the "un-packed" form, see.

Provisional packed designations

The system of packed provisional minor planet designations:

uses exactly 7 characters with no spaces for all designations
compacts 4 digit years to a 3-character code, e.g. 2014 is written as K14 '
converts all subscript numbers to a 2-character code
the packed 2 character subscript code is placed between the half-month letter and the second letter

Contrary to the new-style system, the letter "i" is used in the packed form both for the year and the numeric suffix. The compacting system provides upper and lowercase letters to encode up to 619 "cycles". This means that 15,500 designations within a half-month can be packed, which as of November 2025, only two objects have passed the limit: and.
The Minor Planet Center has extended the [|packed designation] in preparation of the Vera C. Rubin Observatory, which is estimated to discover 250,000 objects will be discovered during its most productive months. With the new scheme, the 15,500th object and all prior ones will still have the usual packed designation, but the 15,501st object and any following ones will have the new designation, in which the first character is a underscore, the second character is a letter symbolizing the last two digits of the year of discovery, the third character being the half month, and the next four being the order of designation after 15,500, using characters from 0 to 9, A to Z, then a to z.
With this scheme, would be _QC0000, while the last designation possible for the first half of February would be, which would be _QCzzzz, but because of the large amount of objects needed to be discovered in one half-month to surpass this limit, this scheme appears to be sufficient. The only two objects that currently have this new designation are and, which are _FB0000 and _FB0001, respectively.
; Examples:
is written as J95X00A
is written as J95X01L
is written as K16EF6K
is written as K07Tf8A
; Description

The year 1995 is compacted to J95. As it has no subscript number, 00 is used as placeholder instead, and directly placed after the half-month letter "X".
The year 1995 is compacted to J95. Subscript number "1" is padded to 01 to maintain the length of 7 characters, and placed after the first letter.

The year 2016 is compacted to K16. The subscript number "156" exceeds 2 digits and is converted to F6, '
The year 2007 is compacted to K07. The subscript number "418" exceeds 2 digits and is converted to f8,

; Conversion tables
Comets follow the minor-planet scheme for their first four characters. The fifth and sixth characters encode the number. The seventh character is usually 0, unless it is a component of a split comet, in which case it encodes in lowercase the letter of the fragment.
; Examples:

1995 A1 is written as J95A010
1995 P1-B is written as J95P01b
2088 A103 is written as K88AA30.

There is also an extended form that adds five characters to the front. The fifth character is one of "C", "D", "P", or "X", according to the status of the comet. If the comet is periodic, then the first four characters are the periodic-comet number ; otherwise, they are blank.
Natural satellites use the format for comets, except that the last column is always 0.

Packed survey designations

Survey designations used during the Palomar–Leiden Survey have a simpler packed form, as for example:

is written as PLS6344
is written as T1S4835
is written as T2S1010
is written as T3S4101

Note that the survey designations are distinguished from provisional designations by having the letter S in the third character, which contains a decimal digit in provisional designations and permanent numbers.

Permanent packed designations

A packed form for permanent designations also exists. In this case, only the designation's number is used and converted to a 5-character string. The rest of the permanent designation is ignored. Minor planet numbers below 100,000 are simply zero-padded to 5 digits from the left side. For minor planets between 100,000 and 619,999 inclusive, a single letter is used, similar as for the provisional subscript number :A covers the number range 100,000–109,999B covers the number range 110,000–119,999a covers the number range 360,000–369,999z covers the number range 610,000–619,999
; Examples:00001 encodes 1 Ceres99999 encodes A0000 encodes 100000 Astronautica A9999 encodes B0000 encodes G3693 encodes 163693 Atira Y2843 encodes 342843 Davidbowie g0356 encodes 420356 Praamzius z9999 encodes
For minor planets numbered 620,000 or higher, a tilde "~" is used as the first character. The subsequent 4 characters encoded in Base62 are used to store the difference of the object's number minus 620,000. This extended system allows for the encoding of more than 15 million minor planet numbers. For example:

is represented as ~0000
:620,000 − 620,000 0 0 × + 0 × + 0 × + 0 ×
is represented as ~000z
:620,061 − 620,000 61 0 × + 0 × + 0 × + 61 ×
will be represented as ~AZaz
:3,140,113 − 620,000 2,520,113 10 × + 35 × + 36 × + 61 ×
will be represented as ~zzzz
:15,396,335 − 620,000 14,776,335 61 × + 61 × + 61 × + 61 ×

For comets, permanent designations only apply to periodic comets that are seen to return. The first four characters are the number of the comet. The fifth character is "P", unless the periodic comet is lost or defunct, in which case it is "D".
For natural satellites, permanent packed designations take the form of the planet letter, then three digits containing the converted Roman numeral, and finally an "S". For example, Jupiter XIII Leda is J013S, and Neptune II Nereid is N002S.