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Nomenclature Rules for Meteor Showers

The new nomenclature rules for meteor showers, presented at the 2022 June 15 Business meeting of the IAU Commission F1, were approved by members of the F1 Commission by vote, which took place electronically from July 15 to July 20, 2022. The new nomenclature rules will not be applied retroactively. All names of meteor showers assigned before August 2022 will continue to be used.

The new rules are based on a two-stage approach. The first stage applies to a new shower just after its discovery. The second stage concerns the repeatedly observed shower, the existence of which no longer raises any doubts.

1st stage – a new meteor shower submitted to the MDC is given a provisional designation only (not a name) based on the date of submission. It is assigned by the MDC according to the following schema:

- a prefix M,

- the year of discovery (4-digit number) followed by a hyphen,

- an uppercase letter identifying the half-month of observation during that year; A for the first half of January, B for the second half, and so on (see Appendix 1),

- a number representing the order of the shower submission to the MDC within that half month.

Example: the first shower submitted to the MDC within the second half of the August, e.g. on August 17, 2022, would be designated as M2022-Q1.

2nd stage – a meteor shower, which has become well confirmed (its regular activity, origin, etc.) and meets the required criteria for established status (Appendix 2), will be given a final designation according to the following schema:

- a prefix M followed by a hyphen,

- the IAU MDC numerical code (a number issued sequentially by the MDC),

- a name (the discoverer will be invited to propose a unique name for their shower; all proposed names will be judged by the Working Group on Meteor Shower Nomenclature of the IAU.)

Example: a shower provisionally designated M2022-Q1 could obtain the final designation M-01212 (18-Aquariids), where 01212 is the sequential numerical code of the shower given by the MDC, and 18-Aquariids the name given by the observer.

Appendix 1.

The table below shows the relationship between the letters of the Latin alphabet and the half-month intervals in the calendar year, used for the provisional designation of meteor showers.

Latin letter

Half month

Latin letter

Half month


Jan. 1-15


Jan. 16-31


Feb. 1-15


Feb. 16-29


Mar. 1-15


Mar. 16-31


Apr. 1-15


Apr. 16-30


May 1-15


May 16-31


June 1-15


June 16-30


July 1-15


July 16-31


Aug. 1-15


Aug. 16-31






Oct. 1-15


Oct. 16-31


Nov. 1-15


Nov. 16-30


Dec. 1-15


Dec. 16-31

Letters I and Z are unused.

Appendix 2.

Criteria for the nomination of showers for established status:

Giving the status of an established shower to a meteor shower means that we are dealing with a real stream and that its parameters (radiant coordinates, velocity and orbit) have been independently determined. Established showers officially receive their names during IAU General Assemblies.

A meteor shower listed in the MDC database can be nominated for established status by anyone if the shower fulfils criteria C1-C3. Criterion C4 is not obligatory but will strengthen the shower candidate’s position.

C1 - The shower is represented by at least two sets of parameters (hereafter called: solution) which have been observed/determined by at least two independent author teams.

C2 - Each solution was identified using at least 15 members of the shower (in the case of single-station observations, at least 50 members) within one period of shower activity.

C3 - The shower’s existence is supported by an evaluation of its statistical significance in the local sporadic background or the existence is supported by an estimate of the probability of a random coincidence of the orbits in the dataset used.

C4 - The stream parent body is known, or there is a candidate for the parent body, or another mechanism of the stream formation is suggested.

Compliance with the C3 and C4 criteria must be confirmed by research and reviewed publication submitted to the MDC.

The Working Group on Meteor Shower Nomenclature of the IAU (WG) must unanimously approve each nomination. Once the WG has approved a suggestion, the President of the WG, in agreement with the President of the F1 Committee, will contact the IAU. Nomination proposals will be presented at meetings of the Committee during the GA IAU. Once the IAU has approved a nomination and the shower has officially received its name, it will be moved from the Working List to the List of Established Showers in the MDC.

To see previous rules, go here.

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 AD 2021, September 10
 M. Hajdukova
and  R. Rudawska