Naming of asteroids and comets

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The naming of asteroids and comets is now based on a two-stage process. Immediately after their discovery, they first receive a so-called provisional name made up of numbers and letters, which essentially contains the date of discovery according to a scheme established by the International Astronomical Union (IAU). After the exact orbit of a newly discovered asteroid has been determined and confirmed by independent observers, the discoverer has the right to propose a name for this object, which is then officially assigned by the IAU taking various criteria into account. Comets, on the other hand, are now always named after their discoverers.

Provisional name

The current naming scheme was created from older systems by extension so that older names are consistent with newer ones.


The provisional name of the newly discovered asteroid or comet is formed by the IAU based on the discovery date from the following components:

Track type A year Half month B number Pass C
Asteroids A. / Observation
A – Y without I Consecutive letter for each half month
(A – Z without I)
Subscript number:
1 = 2nd pass
Comets PXCDI Consecutive number per half-month -
A. Identification of the type of track
  • Comets are preceded by another letter followed by a slash as soon as the orbital elements have been determined more precisely.
  • Objects that were originally thought of as asteroids that turn out to be comets retain their original names. However, like all other comets, they are preceded by the letter characterizing the orbit.

Track type Meaning (German) Derivation (English)
P Short-period comet (The orbital period is less than 200 years or at least two confirmed observations of the perihelion.) p eriodic comet (... less than 200 years or ...)
C. Long-period comet (The orbital period is greater than 200 years.) non-periodic c omet
X The orbit cannot be determined / known (especially historical comets like X / 1106 C1 )
D. Periodic comet that has been lost or no longer exists a periodic comet that has d isappeared (or broken up, or been lost)
I. Interstellar object (so far only two uses: 1I / ʻOumuamua and 2I / Borisov ) i nterstellar object
A. It is found afterwards that it is not a comet, but an asteroid
B. Half month
month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1st - 15th of month A. C. E. G J L. N P R. T V X
from the 16th of the month B. D. F. H K M. O Q S. U W. Y

Exceptions: I omitted due to risk of confusion, Z unused

C. Pass
  • Number of runs through the alphabet (A – Z without I, 25 letters) with appended subscripts starting with 0 for the first run.
  • The 0 for the first round is omitted so that the subscripts only start from 1 for the second round.
  • Due to the limitation of the ASCII character set (and for the sake of convenience), however, the subscript of the run number is often not used.



In 2004, the first asteroid discovered was named 2004 AA , beginning January 1st . This scheme then runs through 2004 AZ , which is then followed by the next run 2004 AA 1 . It will go through until January 16th (according to UTC time); the first letter changes to B and counting continues with 2004 BA . An example for the order of the designations in one half of the month, using the example of the second half of September 1995: 1995 SA, 1995 SB,… 1995 SY, 1995 SZ, 1995 SA 1 ,… 1995 SZ 1 , 1995 SA 2 ,… 1995 SZ 9 , 1995 SA 10 etc.

The celestial body now known under the name (90377) Sedna had the provisional designation 2003 VB 12 . It was discovered in the first half of November 2003 (V) and was the 302nd discovery in this period (B12 → 2 + 12 * 25 = 302).


Comet discoveries are named similarly: 2004 A1 is the first comet discovered in the period January 1-15, 2004, 2004 A2 is the second, etc.

The comet Hyakutake, for example, is also known as C / 1996 B2 . So Hyakutake was the second comet to be discovered in the second half of January 1996. As the C indicates, its orbital period is greater than 200 years.

Permanent name


The names of the asteroids are composed of a prefixed number and a name. The minor planet number used to indicate the order in which the celestial body was discovered. Today it is a purely numerical form of counting, as it is only given when the orbit of the asteroid has been secured (i.e. the object can be found again at any time). This can certainly take place years after the initial observation.

The discoverer has the right to propose a name within ten years after the numbering. However, this must be confirmed by a commission of the IAU, as there are guidelines for the names of astronomical objects . Accordingly, numerous asteroids exist with numbers but without names, especially in the upper ten thousand.

The first asteroid was discovered in 1801 by Giuseppe Piazzi at the Palermo observatory in Sicily . Piazzi baptized the heavenly body with the name Ceres Ferdinandea. The Roman goddess Ceres is the patron saint of the island of Sicily. With the second name, Piazzi wanted to honor King Ferdinand IV , the ruler of Naples and Sicily. This displeased the international research community and this part of the name was left out. The official name of the asteroid is therefore (1) Ceres .

As the discoveries continued, the nomenclature was retained and the asteroids were named after Roman and Greek goddesses ; these were (2) Pallas , (3) Juno , (4) Vesta , (5) Astraea , (6) Hebe etc. Initially, the unwritten law that asteroids were always given female names also applied; this was first broken at the asteroid (334) Chicago .

As more and more asteroids were discovered, astronomers ran out of ancient deities. Asteroids were named after the wives of the discoverers, in honor of historical or public figures, cities and fairy tale characters. Examples are the asteroids (21) Lutetia , (216) Cleopatra , (719) Albert , (1773) Rumpelstilz , (2807) Karl Marx , (5535) Annefrank , (9000) Hal , (17744) Jodiefoster . This practice also produced somewhat curious flowers. For example, the planetoid (1372) Haremari, discovered in 1935, is named in honor of the employees of the Astronomical Computing Institute in Heidelberg, as the harem of the ARI. Another curious example is the asteroid (2309) Mr. Spock , which was named not after the Star Trek character , but after the explorer's cat of the same name. This led the IAU to declare the naming of asteroids after domestic animals undesirable.

In addition to names from Greco-Roman mythology , names of deities from other cultures are also used, especially for newly discovered larger objects, such as (20000) Varuna , (50000) Quaoar and (90377) Sedna .

After the new category of dwarf planets was introduced in 2006 , Ceres kept the number 1, and new numbers from this series were assigned to Pluto, which had previously been classified as a planet , as well as to Eris .

The discovery of the asteroid 1I / ʻOumuamua in November 2017, which is of interstellar origin, made the introduction of a new class, the interstellar celestial bodies, necessary. These are marked with a sequential number followed by an I (for interstellar ) in their name.


Usually a comet is named after its discoverer, for example the comet Shoemaker-Levy 9 is the ninth comet that Eugene and Carolyn Shoemaker discovered together with David H. Levy . A few periodic comets are named after the astronomers who first calculated their orbit: Halley's Comet , for example, is named after Edmond Halley , who was the first to recognize that some past comet observations belong to a comet that recurs at regular intervals of 76 years.

Through systematic automated sky surveys , especially for potentially dangerous earth orbit cruisers , in addition to many asteroids (hence the high number of new discoveries), many new comets are also found by these programs. The name of the group of observers is then added to the provisional name in brackets, in the tradition of naming it after the discoverer. So all comets found by the search program LINEAR have the name component 'LINEAR', or (if the discovery was made by another observer or group of observers at the same time) a combined one, such as B. 'LINEAR NEAT '. For example, the comet with the designation C / 2002 T7 (LINEAR) , which was discovered on October 14, 2002 and reached an apparent magnitude of about 2 mag in May 2004 .

Short-period comets that are secured as such are given a permanent sequential number, followed by a P (the letter coding of their orbit), a slash and the name of the discoverer or orbit calculator. For example, 2P / Encke is the second (after 1P / Halley ) of currently 455 comets (as of January 11, 2019) that has received such a permanent number.

See also

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