by Damir Šegon, Denis Vida and Paul Roggemans
Abstract: A new meteor shower on a Jupiter-family comet orbit (TJ = 2.34 ± 0.16) orbit has been detected during September 23–24 by the Global Meteor Network. Meteors belonging to the new shower were observed between 176° < λʘ < 187° (2024, September 19–29) from a radiant at R.A. = 240° and Decl.= +77° in the constellation of Ursa Minor, with a geocentric velocity of 32 km/s. The new meteor shower has been listed in the Working List of Meteor Showers under the temporary name-designation: M2024-S1.
Introduction
On 26 September 2024, Yury Harachka from Belarus reported that the Belarusian meteor network registered a distinct group of three radiants in the constellation of Ursa Minor during the night of 24-25 September. No corresponding known meteor shower could be found. A fourth registration came from Odessa, Ukraine (Harachka et al., 2024).
At the same time the Global Meteor Network radiant plot for 23-24 September displayed a radiant hot spot not related to any other meteor shower (Figure 1). A quick analysis of the available orbit revealed a concentration of 31 orbits recorded during the nights of 2024 September 23–25 (GMN website). All meteors appeared during the solar-longitude interval 181.0° – 183.0°, with a peak at 181.9°. The shower is similar to but distinct from epsilon-Ursae Minorids (EPU#1044) which have been observed 5 degrees away in 2020 and 2022. A CBET announcement was prepared and published (Vida and Šegon, 2024) and the new meteor shower was registered by the the IAU Meteor Data Center and got the temporary identification M2024-S1.
The shower was independently observed by cameras in 18 countries worldwide (Belgium, Bulgaria, Canada, Croatia, Czech Republic, Denmark, France, Germany, Greece, Hungary, Luxembourg, Mexico, Slovakia, Slovenia, South Korea, the Netherlands, United Kingdom and the USA). The meteors were bright, most having peak magnitudes brighter than +0.0.
Figure 1 – Radiant plot of the Global Meteor Network data for 2024 September 23–24 in Sun-centered geocentric ecliptic coordinates. The new radiant is visible at high ecliptic altitude and marked by a red arrow.
Discovery and first analysis
We used the procedure as described for some recent cases of possibly new showers in Bootes and Draco (Šegon et al., 2023). The Drummond dissimilarity criteria DD has been chosen for the analysis of the new radiant concentration. A first iteration revealed a clear concentration of orbits, as it can be seen on Figure 2. The Railey distribution fit pointed at a DD value of 0.05 as the orbital similarity cutoff (Figure 3), which resulted in 31 orbits representing the possibly new meteor shower.
Figure 2 – Histogram of the distribution of the Drummond DD criterion values valid for the final mean orbit.
Figure 3 – Rayleigh distribution fit and Drummond DD criterion cutoff.
The presence of non-shower radiants in the area around the possibly new shower (Figure 4) shows the cutoff to be reliable since the density of meteor radiants does not look affected after removing shower members (plotted as pale diamonds). The plot of the shower meteor radiants in equatorial coordinates shows a very compact group, with a standard deviation of the distances from the average radiant position of about a single degree (see Figure 5). The Π–i diagram shows a compact group of radiants too (Figure 6), without any other groups of radiants to be seen.
Figure 4 – All non shower meteor radiants in geocentric equatorial coordinates during the shower activity. The pale diamonds represent the new shower radiants plots, error bars represent two sigma values in both coordinates.
Figure 5 – The reverse of Figure 4, now the shower meteors are shown as circles and the non shower meteors as grayed out diamonds. Note that there are no other groups of meteor radiants to be seen in the vicinity of the possibly new meteor shower.
Figure 6 – The diagram of the inclination i against longitude of perihelion Π shows a distinct group of radiants without any other groups to be seen.
The activity period (Figure 7) considered in the first analysis on the first available orbit data was limited to the interval 181° < λʘ < 183° (2024, September 23–24) but it was noticed that more related events could have been detected outside this observing window. A second more in depth analysis was postponed until all orbit data for this period had been processed. The first analysis provided solid proof that a thus far unknown shower had been detected.
Figure 7 – The activity period with the number of orbits identified as new shower members.
The only nearby meteor shower, epsilon-Ursae Minorids (EPU#1044), observed 5 degrees away in 2020 and 2022. The new shower is similar to but distinct from these epsilon-Ursae Minorids, with orbital elements outside of the measurement errors of our new shower (Table 1), although we do not exclude the possibility of the showers being dynamically related.
Table 1 – Known neighboring shower, epsilon-Ursae Minorids (EPU#1044), (Shiba, 2022), compared to the new meteor shower, derived by two different methods.
| EPU | New (Šegon) | New (Roggemans) | |
| λʘ (°) | 181.9 | 181.9 | 181.4 |
| λʘb (°) | 181.02 | 181.0 | 176.2 |
| λʘe (°) | 182.99 | 182.6 | 186.8 |
| αg (°) | 255.0 | 238.3 | 240.3 |
| δg (°) | +82.6 | +77.3 | +77.3 |
| Δαg (°) | –3.35 | – | |
| Δδg (°) | –0.41 | – | |
| vg (km/s) | 33.6 | 32.0 | 31.7 |
| λ (°) | 96.8 | 118.5 | 117.1 |
| λg – λʘ (°) | 274.9 | 296.6 | 295.5 |
| βg (°) | 73.6 | 75.7 | 76.1 |
| a (A.U.) | 2.756 | 3.11 | 3.01 |
| q (A.U.) | 1.003 | 0.994 | 0.995 |
| e | 0.636 | 0.680 | 0.669 |
| i (°) | 57.8 | 53.9 | 53.4 |
| ω (°) | 178.7 | 169.2 | 169.7 |
| Ω (°) | 181.9 | 181.8 | 181.0 |
| Π (°) | 0.6 | 351.0 | 350.8 |
| Tj | 2.49 | 2.34 | 2.40 |
| N | 10 | 31 | 55 |
Another search method
Another method has been applied to check this new meteor shower discovery. The starting point here can be any visually spotted concentration of radiant points or any other indication for the occurrence of similar orbits. The method has been described before (Roggemans et al., 2019). The main difference with the method applied in Section 2 is that three different discrimination criteria are combined in order to have only those orbits which fit different criteria. The D-criteria that we use are these of Southworth and Hawkins (1963), Drummond (1981) and Jopek (1993) combined. Instead of using a cutoff value for the D-criteria these values are considered in different classes with different thresholds of similarity. Depending on the dispersion and the type of orbits, the most appropriate threshold of similarity is selected to locate the best fitting mean orbit as the result of an iterative procedure.
Figure 8 – Radiant plot in geocentric equatorial coordinates for different similarity thresholds, the radiant of the epsilon-Ursae Minorids (EPU#1044) is marked as a yellow diamond.
Figure 9 – Radiant plot in geocentric Sun-centered ecliptic coordinates for different similarity thresholds, the radiant of the epsilon-Ursae Minorids (EPU#1044) is marked as a yellow diamond.
This method detects 55 candidate orbits with similarity criteria better than DD < 0.04, DSH < 0.1 and DJ < 0.1. The concentration of these radiants (red and yellow dots) is obvious in Figures 8 and 9, away from the radiant of the epsilon-Ursae Minorids (marked as a yellow diamond). The mean orbit computed according to Jopek et al. (2006) for the orbits selected using the method of Šegon et al. (2023) is listed as New (Šegon) in Table 1, the mean orbit for the selection using the method of Roggemans et al. (2019) is listed under New (Roggemans). The dispersion of radiants with less good similarity are also shown in Figures 8 and 9, but these orbits were not used to compute the mean orbit to avoid contamination with sporadics. As expected, similar orbits were detected over a longer time span, 176.2° < λʘ < 186.8° (2024, September 19–29).
The concentration of the orbits of the newly discovered meteor shower appears very distinctly in the diagrams of the inclination i against the longitude of perihelion Π (Figure 10). The position of the epsilon-Ursae Minorids is marked as a yellow diamond and appears clearly offset from the new meteor shower orbits. Looking at the velocity distribution for the 55 orbits (Figure 11), the higher the inclination, the higher the velocity, the EPU is outside this diagram.
Looking at a couple less common diagrams like eccentricity e against the longitude of perihelion Π (Figure 12) and inclination i against the perihelion distance q (Figure 13), clearly shows the distance between the concentration of the new meteor shower orbits and the epsilon-Ursae Minorid position.
Figure 10 – Diagram of the inclination i against the longitude of perihelion Π, the radiant of the epsilon-Ursae Minorids (EPU#1044) is marked as a yellow diamond.
Figure 11 – Diagram of the inclination i against the longitude of perihelion Π, colorcoded for the geocentric velocity vg.
Figure 12 – Diagram of the eccentricity e against the longitude of perihelion Π, the radiant of the epsilon-Ursae Minorids (EPU#1044) is marked as a yellow diamond.
Figure 13 – Diagram of the inclination i against the perihelion distance q, the radiant of the epsilon-Ursae Minorids (EPU#1044) is marked as a yellow diamond.
Comparing older data and other datasets
Looking up past years orbit data for Global Meteor Network (2018–2023, 1174206 orbits), we find 68 orbits with DD < 0.04. Two in 2019, 1 in 2020, 9 in 2021, 25 in 2022 and 31 in 2023, spread over different nights. This increase from year to year reflects the expansion of the GMN network. With 8 or 9 orbits in single nights in 2022 and 2023, this shower remained just under the detectability threshold. The SonotaCo net orbit data (2007–2022, 443197 orbits) has only 6 orbits with DD < 0.04, recorded in different years. EDMOND (2001–2023, 508266 orbits), has 15 orbits with DD < 0.04 in different years. The CAMS orbit data (2010–2016, 471582 orbits), has 12 orbits with DD < 0.04, recorded in different years between 2011 and 2016.
The shower has been active in past years but the level of activity was too low for the major video camera networks. The large number of cameras of GMN in 2024 made it possible to detect this weak activity.
Parent body
The parent body search suggests a possible parent body to be 2021 HK12. This object matches the new meteor shower orbit with a similarity criterion DSH = 0.15 (Southworth and Hawkins, 1963) and has orbital parameters:
- q = 1.036 AU,
- e = 0.685,
- i = 47°,
- ω = 168.8°,
- Ω = 187.1°.
Discussion
The nearby epsilon-Ursae Minorids (EPU#1044) with its Jupiter-family comet orbit, and the new meteor shower M2024-S1 maybe dynamically related, but there is a clear offset between both orbits. When we use the orbit given by Shiba (2022) as feed to locate similar orbits we find 11 orbits applying the same similarity criteria as for the new meteor shower. This dataset of 11 orbits has no orbits in common with the dataset with 55 orbits that define the new meteor shower.
The original detection of the epsilon-Ursae Minorids (EPU#1044) by Sato in 2019 (Sato, 2020) was based on 12 orbits recorded by SonotaCo and 7 orbits by CAMS. Shiba (2022) used 10 orbits from 2019 to compute the orbit for EPU#1044. These numbers are very small and at the very limit to estimate a mean orbit for such meteor shower. The number of orbits used to define this new meteor shower is larger and therefore statistically more significant. A too small sample of orbits could imply a selection effect resulting in a slightly different orbit.
Jenniskens (2025) compared the observed variation in ecliptic longitude of the shower radiants in the past and suggests that the 2024 outburst can be a return of the epsilon-Ursae-Minorids, rather than a new meteor shower. The number of detected orbits of this shower can be partly explained as due to the expansion of the GMN camera network but the activity level of this shower in 2024 between solar longitude 181° and 183° was definitely higher than in previous years. In past years meteor orbits were recorded from this new shower but the activity level was too low to catch anyone’s attention.
Conclusion
A possibly new meteor shower in the constellation of Ursa Minor active during 10 days, has been detected in the Global Meteor Network orbit data for September 19–29, 2024. The resulting orbit is a Jupiter-family comet orbit one, with as possible parent body the asteroid be 2021 HK12. The new meteor shower has been listed in the Working List of Meteor Showers under the temporary identification M2024-S1.
Acknowledgment
This report is based on the data of the Global Meteor Network (Vida et al., 2020a; 2020b; 2021) which is released under the CC BY 4.0 license. We thank all the participants in the Global Meteor Network project for their contribution and perseverance, operators whose cameras provided the data used in this work and contributors who made important code contributions.
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