By Paul Roggemans, Damir Šegon and Denis Vida
Abstract: A case study on the June delta Pavonids (JDP#835) based on Global Meteor Network orbit data identified 60 possible JDP-orbits in 2025 and 146 during the period 2021–2025. The increase in number of JDP-orbits in recent years reflects the expansion at the southern hemisphere of the Global Meteor Network and does not indicate any enhanced or unusual activity. The radiant and mean orbit are in good agreement with earlier results and provide an independent confirmation for the existence of this meteor shower, based on Global Meteor Network orbit data.
Introduction
The analysis of a possible new meteor shower in the constellation of Indus 16–17 June 2025 (around λʘ = 85.5°) revealed another concentration of radiant points with its main activity a day earlier nearby the new discovered shower which got the temporary identification M2025-O2 (Vida et al., 2025). A checkup in the IAU MDC Working List of Meteor Showers resulted in a positive identification with the June delta Pavonids (JDP#835), which was reported in 2018 by Jenniskens et al. (2018) based on 11 orbits recorded by the CAMS network in 2014 and 2016. In his book ‘Atlas of Earth’s meteor showers’ Jenniskens (2024), page 751, published newer data on the June delta Pavonids, based on 65 orbits recorded by CAMS until 2023, which hasn’t been included yet in the IAU MDC Working List of Meteor Showers.
A quick search located more than 70 possible JDP members in the Global Meteor Network orbit dataset for 2025 alone. Therefore, it was decided to dedicate an analysis to this so far poorly known meteor shower, to check if it displayed enhanced activity in 2025 and to provide an independent confirmation of this meteor shower for the IAU MDC Working List of Meteor Showers.
The June delta Pavonids are clearly visible on the radiant density map of the Global Meteor Network for June 2025 (Figure 1). In 2024 and 2023 the radiant density maps also show this radiant.
Figure 1 – Heat map with 51531 radiants obtained by the Global Meteor network in June 2025. The position of the June delta Pavonids in Sun-centered geocentric ecliptic coordinates is marked with the red arrow.
The search method
The visible concentration of radiant points was extracted for the time interval of 77° < λʘ < 87°, arbitrarily limited in Sun-centered geocentric ecliptic coordinates with
195° < λ–λʘ < 205° and –40° < β < –30°. This selection includes most of the possible meteor shower members as well as the sporadic sources within this interval. This selection included 91 meteor orbits, used to compute a first mean orbit for this sample. We didn’t use median values to derive a mean orbit since a vectoral solution like the method of Jopek et al. (2006) is more appropriate for orbital elements with angular values.
This first mean orbit serves as a reference orbit to start an iterative procedure to approach a mean orbit which is the most representative orbit for the similar orbits in the sample, removing outliers and sporadic orbits. This method has been described before (Roggemans et al., 2019). Three different discrimination criteria are combined in order to have only those orbits which fit the different criteria thresholds. The D-criteria that we use are these of Southworth and Hawkins (1963), Drummond (1981) and Jopek (1993) combined. The values are considered in different classes with different thresholds of similarity. We consider five different threshold levels of similarity:
- Low: DSH < 0.25 & DD < 0.105 & DH < 0.25;
- Medium low: DSH < 0.2 & DD < 0.08 & DH < 0.2;
- Medium high: DSH < 0.15 & DD < 0.06 & DH < 0.15;
- High: DSH < 0.1 & DD < 0.04 & DH < 0.1.
- Very high: DSH < 0.05 & DD < 0.02 & DH < 0.05.
Figure 2 – The radiant distribution during the solar-longitude interval 74° – 94° in equatorial coordinates, color coded for different values of the DD orbit similarity criterion for 2025.
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. Looking at the radiant plot in equatorial coordinates the radiant area appears stretched which is due to the movement of the Earth on its orbit around the Sun which causes the daily drift of the radiant (Figure 2). The radiant drift was computed to be Δα/Δλʘ = +1.43° and Δδ/Δλʘ = +0.10° relative to λʘ = 84.4°. To study meteor showers it is recommended to use the Sun-centered geocentric ecliptic coordinates since meteoroid streams are part of the solar system with the ecliptic plane as reference for the orbital elements. The movement of the Earth is compensated by subtracting the change in solar longitude. The resulting radiant plot is shown in Figure 3. The low threshold D criteria is obviously too tolerant and dispersed, contaminated with false positives or sporadic orbits. Considering the medium low threshold (DD < 0.08) would result in 74 possible JDP-orbits. The medium high class includes 60 possible JDP-orbits which appears added to the sporadic background without affecting the random distribution of this background (Figures 4 and 5).
Figure 3 – The radiant distribution in Sun-centered geocentric ecliptic coordinates, color coded for different values of the DD orbit similarity criterion for 2025.
Figure 4 – The sporadic radiants in Sun-centered geocentric ecliptic coordinates, with JDP radiants marked in grey for DD < 0.06 for 2025.
Figure 5 – The JDP radiants for DD < 0.06 in Sun-centered geocentric ecliptic coordinates, with the sporadic radiants marked in grey for 2025.
Figure 6 – Diagram of inclination i against the longitude of perihelion Π, color coded for different values of the DD orbit similarity criterion for 2025.
The distribution of the inclination against the longitude of perihelion (Figure 6) shows a large spread in the longitude of perihelion, indicating that this is a rather dispersed old meteoroid stream.
The June delta Pavonids are an annual shower and appears each year in GMN orbit data since 2021. The number of orbits identified per year reflects the expansion of the GMN camera network at the southern hemisphere; one orbit in 2021, none in 2022, 28 in 2023, 41 in 2024 and 60 in 2025, or 130 orbits in total that fulfil the discrimination criteria with DSH < 0.15 & DD < 0.06 & DH < 0.15. Most orbits were obtained by New Zealand and Australian GMN station, some by Brazilian and South African stations. These 130 radiants are plotted in Figure 7, the sporadic background was left away as the data wasn’t extracted for these five years (too many meteors).
Figure 7 – The radiant distribution in Sun-centered geocentric ecliptic coordinates, color coded for different values of the DD orbit similarity criterion for the 130 JDP-orbits obtained during 2021-2025.
Figure 8 shows the radiant distribution in Sun-centered geocentric ecliptic coordinates color code for the variation in geocentric velocity for the period 2021–2025. The drift in Sun-centered geocentric ecliptic coordinates Δ(λ–λʘ)/Δλʘ and Δβ/Δλʘ is very small, almost negligible as well as the drift in geocentric velocity Δvg/Δλʘ.
Figure 9 shows the distribution of the inclination against the longitude of perihelion for the 130 orbits obtained during the past five years and displays the same large dispersion in the longitude of perihelion as the result for 2025 in Figure 6.
Figure 8 – The radiant distribution in Sun-centered geocentric ecliptic coordinates, color coded for the variation in geocentric velocity.
Figure 9 – Diagram of inclination i against the longitude of perihelion Π, color coded for the variation in geocentric velocity for the period 2021–2025.
GMN shower association method
The GMN shower association criterion assumes that meteors within 1° in solar longitude, within 3° in radiant, and within 10% in geocentric velocity of a shower reference location are members of that shower. Further details about the shower association are explained in Moorhead et al. (2020). This is a rather strict criterion since meteor showers often have a larger dispersion in radiant position, velocity and activity period. Using these meteor shower selection criteria, 146 orbits have been associated with the June delta Pavonids in the GMN meteor orbit database and the resulting mean orbit has been listed in Table 1.
This method classifies more meteors as June delta Pavonids than the method based on the threshold of the D-criteria. The shower had a median geocentric radiant with coordinates R.A. = 298.1°, Decl. = –62.9°, within a circle with a standard deviation of ±1.1° (equinox J2000.0) see Figure 10. This is in perfect agreement with the results based on the D-criteria method. The radiant drift is also in good agreement for both methods.
Figure 10 – Dispersion on the radiant position.
Figure 11 – The radiant drift.
The JDP-orbit
With 60 JDP orbits available for 2025, 130 for the past five years based on D-criteria and 146 based on the GMN radiant classification, GMN has twice as much data for this meteor shower than the most recent published results for CAMS (Jenniskens, 2024). This is a lot more than the eleven orbits that were used for the first and only entry about this meteoroid stream listed on the IAU MDC working list. In Table 1 we compare the orbital parameters obtained by CAMS with the results of GMN for 2025 and 2021–2025 based on two different methods. The results are in very good agreement except for the longitude of perihelion Π.
Jenniskens (2024) mentions that the JDP meteoroids penetrate deep, the median begin height is a few kilometers deeper for GMN compared to CAMS. It is not clear if this is due to a difference in camera equipment. Figure 12 visualizes the four different orbits in the solar system, most of it below the ecliptic plane. The orbits differ mainly in semi major axis a and eccentricity e, which both are very sensitive to the slightest uncertainty in the measured velocity. The aphelion for the GMN 21–25 orbit is about 60 AU, as comparison the distance of planet Neptune from the Sun is about 30 AU. Figure 13 shows the orbit in the inner solar system with the intersection at the orbit of the Earth at the ascending node where the JDP orbit crosses from south of the ecliptic to north of it. The meteor shower search routine found some orbits fitting the D-criterion threshold at the descending node but too few to be relevant.
Figure 12 – Comparing the mean orbit obtained by CAMS (green) and by GMN in 2025 (red) and during 2021–2025 (blue for 130 orbits based on D-criteria with DD < 0.06, purple for the 146 based on the GMN classification method) in Table 1. (Plotted with the Orbit visualization app provided by Pető Zsolt).
Figure 13 – Comparing the mean orbit obtained by CAMS (green) and by GMN in 2025 (red) and during 2021–2025 (blue for 130 orbits based on D-criteria with DD < 0.06, purple for the 146 based on the GMN classification method) in Table 1. (Plotted with the Orbit visualization app provided by Pető Zsolt).
The plotted CAMS orbit shows a slight shift away from the GMN solutions which may be the result of working with median values of the orbital elements instead of computing a mean orbit like for GMN. The three solutions for GMN are in perfect agreement. Note that plotting a 3D view of a meteoroid stream orbit relative to the orbits of the planets has some perspective effect depending on the point of view.
Table 1 – Comparing the orbital parameters obtained by CAMS (Jenniskens, 2024) and the mean orbit obtained by GMN for 2025 and for the period 2021-2025, both based on orbits that fulfill DD < 0.06.
| CAMS | GMN 25 | GMN 21–25 |
GMN | |
| λʘ (°) | 83.1 | 84.4 | 83.0 | 82.8 |
| λʘb (°) | 72 | 74 | 74 | 74.6 |
| λʘe (°) | 90 | 91 | 92 | 91.8 |
| αg (°) | 298.1 | 300.7 | 298.1 | 298.1 |
| δg (°) | –63.4 | –62.3 | –62.9 | –62.9 |
| Δαg (°) | +1.74 | +1.43 | +1.62 | +1.63 |
| Δδg (°) | +0.22 | +0.10 | +0.13 | +0.19 |
| vg (km/s) | 39.7 | 39.6 | 39.6 | 39.3 |
| λg (°) | – | 288.1 | 286.5 | 203 |
| λg–λʘ (°) | 203.0 | 203.5 | 203.2 | 203.5 |
| βg (°) | –41.4 | –40.7 | –41.1 | –41.1 |
| Hb (km) | 106.2 | 102.6 | 102.9 | – |
| Hmax (km) | 91.4 | 93.1 | 93.0 | – |
| He (km) | 86.8 | 88.5 | 87.7 | – |
| a (A.U.) | 625 | 38.7 | 30.3 | 18.5 |
| q (A.U.) | 0.584 | 0.570 | 0.574 | 0.573 |
| e | 0.999 | 0.985 | 0.981 | 0.969 |
| i (°) | 56.0 | 56.5 | 56.0 | 55.9 |
| ω (°) | 81.1 | 83.3 | 82.8 | 83.1 |
| Ω (°) | 263.0 | 263.9 | 263.3 | 262.7 |
| Π (°) | 344.2 | 347.2 | 346.1 | 345.8 |
| Tj | 0.60 | 0.65 | 0.69 | 0.80 |
| N | 65 | 60 | 130 | 146 |
The Tisserand’s parameter Tj identifies the orbit as of a long-period comet type. A parent-body search top 10 includes candidates with a threshold for the Drummond DD criterion value lower than 0.30 but none of which can be associated with any certainty (Table 2).
Table 2 – Top ten matches of a search for possible parent bodies with DD < 0.30.
| Name | DD |
| 2020 KC7 | 0.209 |
| 2017 DQ36 | 0.241 |
| C/1978 C1 (Bradfield) | 0.241 |
| 2012 XT134 | 0.245 |
| C/1376 M1 | 0.246 |
| 2015 WG9 | 0.25 |
| (311044) 2004 BB103 | 0.251 |
| 2008 AK33 | 0.254 |
| 2015 YD18 | 0.258 |
| 2016 XK2 | 0.264 |
Conclusion
This case study confirms the existence of the June delta Pavonids (JDP#835) listed in the IAU MDC Working List of Meteor Showers based on 11 orbits obtained by CAMS in 2014 and 2016 (Jenniskens et al., 2018). GMN obtained 60 orbits that fulfil the discrimination criterion threshold with DSH < 0.15 & DD < 0.06 & DH < 0.15. Checking older GMN data, 130 candidate orbits were found. The usual GMN method for shower classification identified 146 JDP meteors. The resulting mean orbit for all three GMN solutions is in good agreement with the result by CAMS published by Jenniskens (2024) which were not yet included in the IAU MDC Working List of Meteor Showers. We propose to consider this meteor shower to be added to the established showers.
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 825 participants in the Global Meteor Network project for their contribution and perseverance. A list with the names of the volunteers who contribute to GMN has been published in the 2024 annual report (Roggemans et al., 2025).
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