Abstract: The very remarkable similarity of the preliminary orbit of Near Earth Asteroid P/2024 OC2 and the alpha Capricornid meteor shower (CAP,#1) is outlined.
Discussion
Following a thread online started on November 11th 2024 on the COMETS-ML group by Peter Bertwhistle on the possibility of P/2024 OC2 showing cometary activity a master database of approximately three million multi-station meteor orbits (including Harvard Photographic, GMN (Vida et al., 2021), SonotaCo (2009), EDMOND (Kornoš et al., 2014) and CAMS (Jenniskens et al., 2018) publicly available data) was tested against the preliminary orbit given by the Minor Planet Center using the Jopek 1993 D criterion. Since article submission the cometary activity has been confirmed in MPEC 2024-V174. Accordingly, the object’s current designation has been updated to P/2024 OC2 here.
Using a D criterion threshold of 0.100 it was found that over 13506 orbits could be matched with the orbit of P/2024 OC2 and that the object is in fact strongly associated with the alpha Capricornid meteor shower (CAP,#1). Several potential candidates for this shower appear in the literature but none of the previously suggested objects match the shower as well as this object and further tests against all other cometary orbits and this object did not match to better than D = 0.100 (16P/NEAT and P/2003 T12 were the nearest comets but with Jopek D Criterion values (Jopek, 1993) of roughly 0.12 for both). Results for potential matches given as number per Jopek D Criterion value range are given in Table 1. It should be noted that the vast majority, over 90%, of these orbits had already been categorized as alpha Capricornids by the respective reporting surveys.
Table 1 – Number of orbits per Jopek D criterion range when matched to the Orbit of P/2024 OC2.
| D value | Number |
| 0.020 – 0.100 | 13506 |
| 0.020 – 0.080 | 10561 |
| 0.020 – 0.060 | 7029 |
| 0.020 – 0.040 | 2565 |
| 0.020 – 0.030 | 762 |
Analysis of the current published orbit of the prospective comet (at time of writing) appears to be inherently very faint, so faint that it is rarely detectable from Earth at magnitudes brighter than approximately 22, barely lasting a week brighter than magnitude 16 when a favorable close approach occurs (probable ones occurred in 1922 and 1973 though no literature notifications of enhanced activity seem to appear for either those or the following years) and barely reaching magnitude 14.5 for around a day at such times. This suggests that the object is both quite small and of very low mass. Such a case would therefore lead to the conclusion of it being an impressively sized meteoroid rather than the parent body of the shower, possibly a fragment of any putative parent body.
Acknowledgment
The publicly available datasets of meteor orbits provided up to current and near current times by GMN, SonatoCo and EDMOND and CAMS 3.0 which lists orbits only up to 2016 were invaluable in this analysis, with the GMN data strongly predominating in number.
References
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Jopek T. J. (1993). “Remarks on the meteor orbital similarity D-criterion”. Icarus, 106, 603–607.
Kornoš L., Koukal J., Piffl R., and Tóth J. (2014). “EDMOND Meteor Database”. In, Gyssens M., Roggemans P., Zoladek, P., editors, Proceedings of the International Meteor Conference, Poznań, Poland, Aug. 22-25, 2013.
SonotaCo (2009). “A meteor shower catalog based on video observations in 2007-2008”. WGN, Journal of the International Meteor Organization, 37, 55–62.
Vida D., Šegon D., Gural P. S., Brown P. G., McIntyre M. J. M., Dijkema T. J., Pavletić L., Kukić P., Mazur M. J., Eschman P., Roggemans P., Merlak A., Zubrović D. (2021). “The Global Meteor Network – Methodology and first results”. Monthly Notices of the Royal Astronomical Society, 506, 5046–5074.
