Abstract: Following the release of MPEC 2024-N106 declaring the newly discovered comet P/2024 L4 Rankin an immediate examination of GMN meteor orbits tested against this published orbit using a discrimination criterion was made revealing a potential, currently unknown, shower. Later on the same day IAUC CBET 5409 gave a more detailed and general announcement of the comet discovery as well as including a short note commenting on a potential association with the δ1 Canis Minorids (DCN#1168). The published orbit for this shower was subsequently tested in the same way against the GMN orbits as the earlier examination had revealed no such connection with this shower. This independently showed that no connection of the latter shower with the comet orbit existed according to discrimination criterion and that there was only a small overlap in GMN meteor orbits with poor discrimination criterion values, and, that the few putative new shower orbits that matched the the δ1 Canis Minorid shower orbit had no individual meteor orbit common to both showers. The names α Canis Minorids and Procyonids are given to the suggested new shower here.
1 Introduction and methodology
MPEC 2024-N106 was released on July 9th 2024 at 02h49m UT announcing the discovery details and preliminary orbital elements for P/2024 L4 Rankin. An examination of the orbit using the Jopek 1993 discrimination criterion variant (henceforth DJ), adopting a threshold value of 0.100 was made against Global Meteor Network data revealing a potential association with 112 meteor orbits. Much later on July 9th 2024 UT CBET 5409 was released also announcing P/2024 L4 Rankin and including a note with respect to the potential association of the comet with the δ1 Canis Minorids (DCN#1168) which has a radiant similar, but somewhat offset, in celestial coordinates and solar longitude to those that which can be predicted from the comet’s orbit, with a similarly scaled offset in geocentric velocity (these being the most readily derived and primary measures of a meteor event from which other details are then derived when multi-station data are utilized).
Accordingly, the earlier analysis was repeated using the published orbital elements for this latter suggested shower as given in Jenniskens 2024. The Jopek 1993 variant, DJ, was again utilized and the δ1 Canis Minorid orbital elements were tested against both the published comet orbit and the earlier potential new shower association that had been derived from GMN meteor orbits, as well as the full GMN dataset of meteor orbits, the latter resulting in 146 matched meteor orbits. A cross match of the Procyonid candidates was also made against these candidates leading to 13 objects from each being matched, however with poor DJ values and no meteor common to each.
2 Results
When the orbit for P/2024 L4 Rankin is tested against the complete Global Meteor Network (GMN) dataset up to and including July 2024 112 comets are found to be associated using DJ < 0.100, albeit with very few bettering the value of 0.08 or so, most of them being in the 0.09 to 0.10 range. These are referred to as the Procyonids here.
When the published orbital elements for P/2024 L4 Rankin are compared to those of the published δ1 Canis Minorid orbital elements the DJ value returned is 0.172, where the published suggested threshold value for this criterion is 0.105 and 0.100 was used here. Given the tighter rein this criterion has compared to others and the fact that the value does not follow a linear relation this is quite a large offset demonstrating no similarity between the two orbits. Further the comet has a somewhat stable orbit with an aphelion well distanced from that of Jupiter and is not particularly perturbed by said (not significantly differently from any other general solar system object that is influenced by Jovian gravity). There is no evidence of connection between this shower and this comet based on their representative orbits nor any evidence of any perturbation upon the comet’s orbit.
When the 112 putative Procyonid meteor orbits derived from GMN data using DJ against P/2024 L4 Rankin’s published orbit are tested against the 146 δ1 Canis Minorid meteor orbits derived from GMN data using DJ against their published orbit 13 matched objects are found for each shower, albeit predominantly with DJ values mostly well above 0.09, i.e. near the threshold value limit, giving a total of 26. None of these meteor orbits were common to both showers and only uniquely matched their shower neighbors, despite being matched when matched across showers via DJ, thus 13 meteors per shower could be shown to have a connection using this test but none were shown to be the same as any meteor in the other shower.
The resulting elements are given in Table 1 for four orbits, the comet, the published δ1 Canis Minorid orbit, the mean δ1 Canis Minorid orbit derived from GMN data and the mean Procyonid orbit derived with GMN data (both with the 13 common orbits removed as an extra filtering), with the parenthetic values for P/2024 L4 being predicted from its orbital elements. The 13 matched orbits have been removed from the 112 meteor orbit Procyonid dataset as their relation to either shower cannot be affirmed, leaving 99 orbits, similarly the δ1 Canis Minorid dataset had its 13 matched orbits removed and becomes reduced to 133 orbits.
It should be strongly noted, however, that no specific meteor orbit was common to both the 112 meteor Procyonid dataset and the 146 meteor δ1 Canis Minorid dataset, potential connections only appearing due to the use of a discrimination criterion cross match of said datasets. That is, all GMN meteor orbits within each shower’s dataset were unique to that particular dataset and no particular/specific meteor could be shown to associated with both showers.
Low inclination comet orbits within that of Jupiter can be problematic the nearer they are to the solar system’s orbital plane, with unassociated meteors appearing related due to the assumed random background distribution not being valid the nearer to the orbital plane inclination becomes. For example, orbital inclinations of 5 or less degrees can be found to match with several Jupiter family comets and/or showers when using discrimination criteria. Accordingly, in order to assess this potential contamination, a handful of artificial orbits with the same elements and inclination as the comet but with the argument of perihelion and the ascending node reversed as well as those two elements randomly chosen but the same offset in values kept were also used to assess the situation, as given a sufficiently non-random distribution of orbits biased by perturbations by their proximity to the ecliptic plane any low inclination orbit, real or not, has the potential to find matches in meteor orbit datasets of sufficient size. Fortunately, these tests gave no such matches.
Table 1 – Particulars and orbital elements for P/2024 L4 Rankin the δ1 Canis Minorids (DCN#1168) and the Procyonids.
| Entity | RA | Decl. | λʘ | vg | q | e | i | ω | Ω |
| P/2024 L4 | (111.5) | (+6.5) | (297.1) | (19.9) | 0.672 | 0.699 | 10.1 | 53.7 | 139.8 |
| δ1 CMi publ | 110.6 | –0.1 | 293.2 | 23.6 | 0.622 | 0.78 | 16.1 | 80.5 | 113.2 |
| δ1 CMi calc | 110.9 | –0.4 | 293.6 | 23.4 | 0.625 | 0.775 | 16.1 | 80.5 | 113.6 |
| Procyonid | 113.8 | +6.2 | 303.5 | 19 | 0.715 | 0.705 | 9.1 | 70.1 | 123.5 |
Simple plotting of either radiant positions for each meteor orbit or graphical representations of the orbits themselves reveals distinct offsets in perihelion distance and inclination between the δ1 Canis Minorids and both the proposed Procyonids and the P/2024 L4 Rankin orbit whilst the latter lies amongst the spread of Procyonid orbits quite well.
3 Discussion
Recent times have seen the latest guidelines from IAU working group for meteor shower nomenclature being ignored in publications with in some cases suggested names being given to showers instead of the recommended preliminary code, and in at least two cases names being suggested in publications by author(s) who are not the showers’ discovery authors! Also, the IAU Meteor Data Centre has over time removed showers with no hint of reference to them on their webpages in some cases without full consideration of the role of nomenclature with respect to historic bibliographic linkage. That is some current mnemonic code identifiers used for some current showers that have been published have been used for showers published in the past that have now been rejected, which can cause confusion during literature searches and lead to much unneeded investigation into what is actually happening. In some cases, there is no record of the former rejected shower and/or designation given at IAU MDC.
In recent times Flamsteed numbers have been added to the naming conventions due to the increased number of showers discovered and/or difficulties in finding a near enough star for naming basis and/or a unique mnemonic/acronym, with in extreme cases variable star designations even being used for shower names! Meanwhile, comet identifiers are not allowed and in any case can no longer be used due to comets being able to cause more than one shower (e.g. 1P/Halley) and also because under current comet nomenclature regulations the named comets no longer have an ordinal number attached when the discoverer already has comets named after them (in other words, different showers could end up being the something Rankinids with no ready clarification as to which of the several Rankin comets that exist is the relevant one from that name, or in yet other words, comet Rankin has no ranking). Indeed, often the comet name is only used in the initial announcement with the comet being referred to in literature by its identifier (although bright ones announced to the general public are often identified by only their name, e.g. NEOWISE, although the press often invents nicknames instead, e.g. Green Comet and Devil Comet), and the use of P/2024 L4-ids is somewhat clumsy, if not very clumsy.
Proper names for stars in many instances predate even Bayer designations, and in many cases are as old as the proper names for constellation used in meteor shower nomenclature. What is more official star proper name lists compiled by the IAU exist.
Given the above points, and especially recent instances of showers being named by non-discoverers when the actual discovers neglected to give a suggested name for once the shower is confirmed I am left with no choice but to name this shower the Procyonids in this publication, its working identifier by regulation would be M2024 L1 utilizing the comet discovery date but M2024 N1 using this discovery shower and paper date.
4 Conclusion
The orbit of recently discovered comet P/2024 L4 Rankin is shown to have meteor orbits from the Global Meteor Network database to be associated with it. The comet has orbital elements, especially the aphelion distance, precluding any readily indicated perturbation due to Jupiter which could have led to past orbits and different resultant shower details. Examination of similar orbits against the full GMN dataset where only the argument of perihelion and the ascending node are changed for the comet orbit shows null results when inspecting whether the near ecliptic plane Jupiter family comet derived population of meteor orbits tested with the Jopek 1993 discrimination criterion can lead to false positives. This suggests some validity to the usage of that criterion for this comet’s orbital association with meteors and a likely lack of false positives amongst the results.
CBET 5409 noted that an association with the unconfirmed published meteor stream the δ1 Canis Minorids was a possibility, however utilizing GMN orbital data it can be shown that that shower is distinct from both the comet and the newly suggested shower detailed here, albeit with some relatively minor overlap between the two showers albeit only via discrimination criterion with no actual specific meteor being shown to be common to both showers. Accordingly, P/2024 L4 Rankin is not associated with the δ1 Canis Minorids even though the comet has a potential associated meteor shower, and the potential associated meteor shower is similarly not associated with the δ1 Canis Minorids.
Due to extenuating circumstances beyond the author’s control the name Procyonids is used for this shower here, although the alternative name of α Canis Minorid shower (alpha-Canis Minorids) is unused and equally applicable upon any confirmation of this shower. If current somewhat half policed IAU nomenclature naming rules are followed the shower would receive the identifier M2024-N1 based on discovery date.
Since this paper was written the identifier M2024-N1 has already been used in a publication’.
Acknowledgents
The online data services for the Minor Planet Center at the Harvard and Smithsonian Center for Astrophysics were utilized for obtaining the comet orbit details. The GMN meteor survey group and especially their volunteers and operatives are expressly thanked not only for their work but for making their data not only public but in near real time and thus available for analytical examination by all in a timely manner when novel events occur.
References
Jenniskens P. (2024). Atlas of Earth’s Meteor Showers. Page 663.
Jopek T. J. (1993). “Remarks on the meteor orbital similarity D-criterion”. Icarus, 106, 603–607.
