Nomenclature Rules for Meteor Showers

New meteoroid streams (meteor showers) may be named according to the following general rule:

[N-S] [D- ] [M- ] [S- ]-[Constelation] [C-]

where [N-S] - Northern-Southern branch; [D- ] - daily activity; [M- ] - month; [S- ] - star designation; [C- ] - complex.

The Constelation component is mandatory, the others are optional. The order of the components is also mandatory.

1. [Constelation] A new meteor shower (and a meteoroid stream) should be named after the constellation that contains the star nearest to the shower radiant. The name should be composed of the possessive Latin name of the constellation. If the Latin name contains one of the following suffixes: ae, is, i, us, ei, ium, or orum - it should be replaced by id, or plural ids. For example, meteors with radiants in Aquarius are Aquariids, in Orion are Orionids, in Ursa Major are Ursae Majorids. However, in the case of the constellation of Hydrus, the meteors are called Hydrusids, in order to avoid confusion with meteors radiating from the constellation of Hydra.

1.1 When the name of a constellation consists of two parts, e.g. Canes Venatici (Latin possesive Canum Venaticorum), then the shower name is Canum Venaticids. Only the second part of the constellation's possessive form is modified by ids.

1.2 When the activity of a shower extends over the boundary of two constellations, its name may contain the corresponding Latin forms of both constellations connected by a dash, e.g. Cepheids-Cassiopeiids, Puppids-Velids, Canum Venaticids-Bootids.

The options (S-, M-, D-, and N-S) are as follows:

2. [S-] If there is more than one radiant in a constellation then, additionally, the designation of the star (designated in Bayer or Flamsteed systems) nearest to the radiant is assigned to the shower. A lowercase Greek or Latin letter is used in the Bayer designation system, a number in the Flamsteed designation system. To avoid any confusion, the two components should be separated by a dash, e.g. alpha-Capricornids, 49-Andromedids.

2.1 If a meteor shower radiant is near the border of a constellation and the nearest star is in the neighboring constellation, then the shower is named after that star and constellation.

3. [M-] If necessary, one may add the name of the month of the shower activity so that showers from the same constellation can be distinguished. The name of the month may appear immediately before the Latin form of the constellation name, e.g. October Draconids, or before the Bayer or Flamsteed star designation, e.g. July mu-Serpentids, October 6-Draconids.

3.1 When the shower activity extends over two consecutive months, the name of the stream may contain the names of both months separated by a dash, e.g. September-October Lyncids.

4. [D-] For daytime showers, it is customary to add 'Daytime' to the Latin form of the constellation name, e.g. Daytime Arietids, or in more complex cases: Daytime kappa-Librids, Daytime April Cetids or Daytime June alpha-Orionids. To be called a daytime shower, its radiant should be at an angular distance less than 32 degrees from the Sun center.

5. [N-S] If necessary, the names of the shower may be supplemented, on the left, by the words 'Northern' and 'Southern'. This refers to cases where meteoroid streams originated from the same parent body and have radiants situated north or south of the ecliptic plane. Acceptable names of a shower are, for example, Northern Taurids, Southern Daytime May Arietids, Northern December omega-Ursae Majorids, etc.

6. [C-] In the case of groups of streams, e.g. from the same parent body, the name of the group is created analogically to a single stream, but supplemented from the right with the word Complex, e.g. delta Aquariid Complex, Daytime May Arietid Complex, Southern Librids-Lupids, etc. In order to better distinguish more complex groups, names containing the Roman numerals 'I', 'II'' ... preceding the word Complex are also allowed, e.g. Centaurid II Complex, Puppid-Velid I Complex, etc.

Apart from the rules listed above, there is an exception for major showers that have been known for many years. Their traditional names, e.g. Perseids, Quadrantids, alpha-Monocerotids, are accepted, even if they do not follow the naming rules; however, the names of the streams which were named after the parent body, e.g. Giacobinids, Halleids, are not accepted.

If the meteoroid stream is encountered at the other node, it is customary to speak of 'twin showers'. The Orionids and eta-Aquariids are twin showers, even though each represent dust deposited at different times and are now in quite different orbits. As a matter of custom, twin showers and the north and south branches of a stream carry different names. Meteor showers are not to be named after their parent bodies (e.g., Giacobinids, IRAS-Araki-Alcockids). The names of comets tend not to be Latin, making the naming not unique. Also, comet names can change when they get lost and are recovered.

The Working Group for Meteor Shower Nomenclature will choose among possible alternative proposed names for newly identified meteor showers, in order to establish a unique name for each meteor shower (e.g., eta-Lyrids, not May Lyrids).