The purpose of the IAU working list of meteor showers is to keep the literature on meteor showers transparent by attributing a unique name to each meteor shower, a three-letter code, and a number. The list has been rapidly expanded in recent years. The multitude of similar meteor shower entries, showers that were never documented in any publication, and the lack of a process to remove showers from the list, caused confusion in the meteor community. A short overview of some recent decisions and the current status is presented.
1 Introduction
Ever since observers noticed that meteors could be identified as shower members by their backwards produced path intersecting its shower radiant, this appeared to be a reliable method to determine new weak showers. The intersections produced by these single station trails resulted in large numbers of poorly documented radiant lists, most of which were just spurious and statistically not significant. Single station minor shower observations caused a lot of controversy.
A more reliable way to define meteor showers is to use orbits. Past 10 years, many video camera networks produced large numbers of orbits which allowed to search for minor meteor streams. In order to coordinate meteor shower definitions and to manage a reference list of meteor showers, the IAU dedicated a working group to take care of this task. The IAU Meteor Data Center (MDC) is responsible for the management of the IAU meteor shower Working List, under the auspices of Division F (Planetary Systems and Bioastronomy) of the International Astronomical Union.
The purpose of the list is to keep the literature transparent. That is done by attributing a unique name to each meteor shower, a three-letter code, and a number. Any newly discovered showers can be added when the discovery has been published in a paper, or if the paper has at least been submitted for publication.
2 Short historic review
A task group on meteor shower nomenclature was established in 2006 at the IAU General Assembly in Prague, Czech Republic. The task group was transformed into the Working Group of Shower Nomenclature at the IAU General Assembly in Rio de Janeiro, Brazil in 2009. The members of the committee are elected at the IAU General Assembly for a term of 3 years (Spurny et al., 2006; Jenniskens, 2006, 2007, 2008; Jopek and Jenniskens, 2011; Jopek and Kaňuchová, 2017).
The task of the working group is to establish a descriptive list of established meteor showers that can receive official names during the IAU General Assembly.
3 Decisions at Meteoroids 2019
Thursday 20 June the members present at the Meteoroids conference in Bratislava met to discuss the status of the Working list. Dr. Peter Jenniskens chaired the meeting and stressed that the purpose of the working list is to properly identify meteor showers described in literature and not to completely document meteor showers.
The large number of meteor showers added in recent years tend to inflate the working list and many entries might be either showers already listed with a different name or just spurious entries. The number of showers listed is not a real concern. The fact that no orbital data or incomplete orbital data were listed is not a concern. It was not approved to remove showers based on these being insufficiently documented. Exceptionally, showers that were very well observed, but without any orbits recorded, should be included if enough evidence is available for the existence of the shower, e.g. a strong outburst.
What is a concern is that several entries were accepted in recent years which were announced to be submitted for publication while the publication never happened. It was suggested that these showers would be moved to the list of removed meteor showers or completely deleted. To avoid this situation in the future a proof of submission of the paper should be delivered in case of newly discovered meteor showers.
Another concern are the duplicates and spurious entries. At the meeting it was decided to remove meteor showers that do not exist. The arguments why a shower is considered not to exist must be published in a peer reviewed journal. Editors of amateur journals (WGN, Journal of the IMO, MeteorNews, Radiant, etc.) are suggested to review any such papers, perhaps by the members of the Working Group. Papers that suggest removal of meteor showers from the list should be sent to the Meteor Data Center and the proposed removal will be evaluated. The reason for removal should be mentioned. Reasons for removal can be “duplicate”, “not statistically significant”, etc.).
Proposed showers that were not published in a paper are deleted from the list and NOT added to the list of removed meteor showers. The codes and numbers become again available. New shower discoveries must be documented in a paper to be submitted within half a year to the Meteor Data Center after requesting the shower name and number. These new showers will no more be listed “pro-tempore” before a paper has been submitted to a journal.
Another change concerns the shower duration, radiant and speed dispersion which were not included before. It was decided to add a look-up table listing the additional data in units of Solar Longitude, Sun-centered Ecliptic Longitude, Ecliptic Latitude, Geocentric Velocity and the IAU shower number.
As a result of these decisions, the list now contains 795 meteor showers of which 112 are established showers, 24 are shower complexes and 659 showers remaining on the working list, being documented in the scientific publications. A list of 172 removed showers remains accessible as archive of names used in the past. In total 137 showers were permanently deleted because there was no known publication that documented the discoveries.
4 What to do when a new shower is discovered?
Amateurs who run a camera network to collect orbits may detect unknown meteor showers whenever some unknown source produces an outburst when Earth passes through its previously unknown dust trail. This kind of ‘discoveries’ represent very valuable contributions to meteor astronomy. However, care should be taken to verify the statistical relevance of groups of similar orbits. To check the likely similarity of orbits, the so-called discrimination criteria are popular tools to check if different orbits may be part of the same meteor shower. The relevance of the D-criteria depends a lot on the type of orbits considered. For instances short period orbits embedded in the rich dust layer around the ecliptic may easily fit D-criteria although there is absolute no physical connection between the orbits. For instance, using the D-criterion of Southworth and Hawkins (1963) as only criterion will very likely result in large collections of similar orbits. Anyone may derive large numbers of showers from these types of orbits all fitting very well the D-criteria although being statistically pure chance associations and thus producing nothing else than false positives for meteor shower detections.
Before any new shower discovery is being claimed, the statistical relevance of the orbit associations should be carefully checked. In case of a reliable discovery, the facts should be documented in a paper to be submitted to a scientific journal, including online journals, which may include eMeteorNews.
In order to publish a paper on a newly identified meteor shower, a proper name for the shower, its IAU code and shower number should be requested. When requesting, send a draft of the manuscript that documents the discovery to the Meteor Data Center. The contact person for the IAU Working Group on Meteor Shower Nomenclature and its Working List of Meteor Showers (https://www.ta3.sk/IAUC22DB/MDC2007/) is Tadeusz Jopek (jopek at amu.edu.pl).
Acknowledgment
The author wishes to thank Peter Jenniskens and Tadeusz Jopek for reviewing this report and for the information provided.
References
Jenniskens P. (2006). “The I.A.U. meteor shower nomenclature rules”. WGN, Journal of the International Meteor Organization, 34, 127–128.
Jenniskens P. (2007). “The I.A.U. meteor shower nomenclature rules”. In, Bettonvil F., Jac J., editors, Proceedings of the International Meteor Conference, Roden, the Netherlands, 14–17 September 2006. Published by IMO, pages 87–89.
Jenniskens P. (2008). “The I.A.U. meteor shower nomenclature rules”. Earth, Moon, Planets, 102, 5–9.
Jopek T.J. and Jenniskens P.M. (2011). “The Working Group on Meteor Showers Nomenclature: A History, Current Status and a Call for Contributions”. In, W.J. Cooke, D.E. Moser, B.F. Hardin, and D. Janches, editors, Meteoroids: The Smallest Solar System Bodies, Proceedings of the Meteoroids Conference, held in Breckenridge, Colorado, USA, May 24-28, 2010. NASA/CP-2011-216469., pages 7–13.
Jopek T.J. and Kaňuchová Z. (2017). “IAU Meteor Data Center-the shower database: A status report”. Planetary and Space Science, 143, 3–6.
Southworth R. R. and Hawkins G. S. (1963). “Statistics of meteor streams”. Smithson. Contrib. Astrophys., 7, 261–286.
Spurny P., Watanabe J.-I., Mann I., Baggaley W.J., Borovicka J., Brown P.G., Consolmagno G.J., Jenniskens P., Pellinen-Wannberg A.K., Porubcan V., Williams I.P., Yano H. (2006). In, Karel A. van der Hucht, editor, Proceedings of the Business Meeting of Commission 22, Meteors, Meteorites and Interplanetary Dust. Transactions IAU, Vol. 26b. International Astronomical Union, pages 140–141.
