New meteor shower in Cetus (M2026-R1)

By Paul Roggemans, Denis Vida, Damir Šegon, Milan Kalina, James M. Scott, Jeff Wood

 

Abstract: A new meteor shower on a Halley-type comet orbit (T_J = –0.35) has been detected during about one day (λ_ʘ 115.0°–116.2°) in 2026, by the Global Meteor Network. In total, 49 meteors from 2019–2026 belong to the new shower from a radiant at R.A. = 36.7° and Decl. = –17.7°, with a geocentric velocity of 63.5 km/s. Maximum activity occurred at λ_ʘ = 115.5°±0.25° (July 18). The shower is also present in GMN data of 2024 and, marginally, 2023. The new meteor shower has been listed in the IAU-MDC Working List of Meteor Showers under the preliminary name-designation: M2026-R1.

 

1  Introduction

A routine screening of the Global Meteor Network radiant density maps revealed an unexpected and unidentified activity source in the constellation of Cetus on 17–18 July 2026. A first analysis revealed 54 meteors of this possible meteor shower of which 37 remained for further analysis after removal of all outliers. The shower had a geocentric radiant with coordinates R.A. = 36.6°, Decl. = –18.5° (equinox J2000.0) at its discovery. The median Sun-centered ecliptic coordinates were λ_g – λ_ʘ = 271.9°, β_g = –31.1°. The geocentric velocity was 62.2 ± 0.2 km/s. The new meteor shower was reported to the IAU-MDC and registered under the temporary identification M2026-R1.

2  Shower classification based on radiants

The first analysis has been done using the tool RadiantMap developed by Milan Kalina. This tool makes it possible to select radiants on the radiant density map (Figure 2) within a range in solar longitude to run automatically the meteor shower association tools developed by Denis Vida and Damir Šegon. Figure 2 shows no known activity expected according to the IAU-MDC Working List of Meteor Showers (Jopek and Kaňuchová, 2017; Jenniskens et al., 2020) at the region of interest, marked by a yellow circle. The MDC solutions closest to M2026-R1 are M2025-P1 (Šegon et al., 2025; 7.2° away, D_D = 0.247, D_SH = 0.717), TCT#598 (8.2°, no orbit), FOR#1066 (12.6°, D_D = 0.133, D_SH = 0.403), SCE#1070 (12.1°, D_D = 0.143, D_SH = 0.417), RER#738 (14.9°, D_D = 0.155, D_SH = 0.427) and ERI#191 (D_D = 0.165, D_SH = 0.449 against Jenniskens, 2023), with D values relative to the radiant-method orbit in Table 1. The maximum-sigma test of Jopek et al. (2024) separates all of them from M2026-R1: they differ by 6° to 19° in λ_g – λ_ʘ (limit 5°), and those with orbits by 14° to 51° in ω (limit 9°).

 

The RadiantMap tool initially selected 54 meteors within the region of interest. About 15% of the candidates are duplicate solutions of the same meteor. They were not removed, but the activity in 115.0°–116.2° remains significant without them (Section 3). The initial radiant offset threshold is 4.35° and the v_g deviation threshold 2.5 km/s. Using these values to remove outliers, 37 meteors remained for final analysis. The final median dispersion is 1.7° giving an association radius (×2.5) of 4.2° (Vida et al., 2021, implemented in the RadiantMap tool). 98 GMN-cameras in 9 countries (Australia, Brazil, Croatia, Czech Republic, Hungary, New Zealand, Poland, Slovakia and the United States) contributed data to this dataset for the radiant based analysis. The shower parameters as obtained by the radiant method for 2026 are listed in Table 1.

Figures 4 and 6 show the relatively compact radiant of M2026-R1 whose activity occurred above the minimal level of detectability only between solar longitude 115.0° and 116.2°.

 

 

 

 

 

3  Shower classification based on orbits

A completely independent meteoroid stream search has been applied to orbit data obtained between solar longitude 112° and 119° during the years 2019–2026. The method has been described in detail in a separate publication (Roggemans et al., 2026a). 70217 orbits were available within this time interval and a final mean orbit has been computed by the method of Jopek et al. (2006) for the thresholds D_SH < 0.125 and D_D < 0.05 and D_J < 0.125 (Southworth and Hawkins, 1963; Drummond, 1981; Jopek, 1993). The Rayleigh fit failed in this case. The threshold was chosen as a safe criterion to assess the similarity among these high-eccentricity retrograde orbits. The resulting mean orbit based upon 49 meteors recorded from 2019 until 2026 is listed in Table 1.

Figures 7, 8, and 10 to 13 plot the combined thresholds D_SH < 0.15 and D_D < 0.06 and D_J < 0.15 (marked as D_D < 0.06), D_SH < 0.125 and D_D < 0.05 and D_J < 0.125 (marked as D_D < 0.05), D_SH < 0.10 and D_D < 0.04 and D_J < 0.10 (marked as D_D < 0.04) and D_SH < 0.05 and D_D < 0.02 and D_J < 0.05 (marked as D_D < 0.02).

 

A radiant concentration is visible between λ_ʘ 114.5° and 116.5° (Figure 7) but beyond this period nothing stands out of the background activity. The eta-Eridanids appear at the same declination west of the new activity. Just south of it are the Fornacids (FOR#1066). The radiant of M2026-R1 is more distinct in the geocentric Sun-centered ecliptic coordinates (Figure 8). The dark cluster right of M2026-R1 are the eta-Eridanids, which have their maximum twenty days later. The concentration south of these is the Fornacids.

 

 

 

The number of shower meteors as a percentage relative to the total number of meteors recorded in a 24 hours interval results in the profile plotted in Figure 9. The highest percentages occurred at λ_ʘ = 115.5° ± 0.25° although similar orbits were detected during the entire search window λ_ʘ = 112° until λ_ʘ = 119°. The possible shower members outside the about one day (λ_ʘ 115.0°–116.2°) interval are likely sporadic meteors that fit the similarity criteria by chance. The radiant based method suffered contamination with sporadics that fit the radiant and geocentric velocity selection criteria (41 candidates against 27 expected sporadics over 112.1°–118.8° in 2026, but 15 against 4.8 within 115.0°–116.2°), but with a heliocentric velocity that is slightly lower than for M2026-R1 meteors. The presence of meteors with a lower heliocentric velocity results in a mean orbit with a lower eccentricity and consequent shorter semi-major axis. The activity period in Table 1 is the search window and represents mainly sporadic contamination beyond the about one day (λ_ʘ 115.0°–116.2°) activity.

We also counted GMN orbits within 4° of the Sun-centered radiant (λ_g – λ_ʘ = 271.9°, β_g = –31.1°) with v_g within 10% of 62.2 km/s, after quality cuts and removal of duplicates, in the window 115.0°–116.2° of each year. The expected number of sporadics was obtained from the fraction of all orbits in the same selection outside this window (λ_ʘ 105°–126°, same year) times the number of all orbits inside it, and P is the Poisson probability of at least the observed number arising from this background alone. The shower fraction was 4.7 per mille in 2023 (5 meteors, 1.4 expected, P = 0.013), 7.3 in 2024 (8, 1.9 expected, P = 0.0009), 3.2 in 2025 (7, 4.1 expected, P = 0.13) and 5.5 in 2026 (15, 4.8 expected, P = 0.0002), with one meteor in 2019 and none in 2020–2022. With the same selection, the 2019–2026 data also show a weaker excess between solar longitude 118.5° and 121.5°: 58 meteors against 36.1 expected (P = 5 × 10⁻⁴). Its relation to M2026-R1 is not yet clear.

4  Orbit and parent body

The diagram of the inclination i versus the longitude of perihelion Π shows quite some dispersion in both inclination and longitude of perihelion (Figure 10). The dense cloud between 270° and 280° in longitude of perihelion and near 110° in inclination are the zeta-Cassiopeiids (ZCS#444).

 

 

The eccentricity e versus the longitude of perihelion Π appears dispersed in e and in Π (Figure 11) because of the sensitivity of the eccentricity for the uncertainty on the velocity measurement for high eccentricity values. The diagram e versus i (Figure 12) also shows a large dispersion. The diagram with the perihelion distance q versus i (Figure 13) shows a dense concentration at the upper limit for the perihelion distance. The ascending node lies at 1.013–1.014 AU and the argument of perihelion is about 355°, so the perihelion sits just inside the node and q of about 1.01 AU follows from the encounter geometry. The q concentration is expected for any stream met at this node and says little about compactness.

Table 1 – Comparing solutions derived by two different methods, RadiantMap-method based on radiant positions for 2026 as reported to the IAU MDC, and the orbit association method (2019–2026) for D_SH < 0.125 and D_D < 0.05 and D_J < 0.125 (D_D < 0.05). H_b, H_e, H_p are the begin-, end- and peak-brightness heights and Mag_Ap is the average peak absolute magnitude, normalized to 100 km. The RadiantMap 2026 selection includes orbits with e > 1. The D-criteria based method eliminated all e > 1.

	RadiantMap method 2026	Orbit method 2019–2026 DD < 0.05
λʘ (°)	115.4	115.6
λʘb (°)	112.1	112.1
λʘe (°)	118.8	118.9
αg (°)	36.6	36.7
δg (°)	–18.5	–17.7
Δαg (°/°λʘ)	+0.66	+0.70
Δδg (°/°λʘ)	+0.51	+0.13
vg (km/s)	62.2	63.5
Hb (km)	109.5	109.9
He (km)	96.1	95.8
Hp (km)	100.9	100.0
MagAp	–1.6	–1.6
λg (°)	27.27	27.5
λg – λʘ (°)	271.87	272.0
βg (°)	–31.11	–30.5
a (A.U.)	7.316	12.6
q (A.U.)	1.011	1.012
e	0.862	0.920
i (°)	127.1	128.7
ω (°)	355.2	354.5
Ω (°)	296.2	295.7
Π (°)	291.5	290.2
TJ	–0.01	–0.35
N	37	49

 

The orbit-based solution removed orbits with too low heliocentric velocities at each step of the iteration procedure until it converged on the final mean orbit listed in Table 1. This solution has a higher eccentricity, larger semi-major axis and slightly higher inclination because of the higher heliocentric velocity with a median v_h = 41.0 km/s as the iteration removed all outliers below 40.12 km/s and above 41.66 km/s so that no e > 1 orbits remain in the threshold class D_SH < 0.125 and D_D < 0.05 and D_J < 0.125. The radiant based method has a median v_h = 40.1 km/s with outliers between 37.22 km/s and 43.22 km/s and contains considerable sporadic contamination. The semi-major axis remains poorly constrained (about 10–15 AU) because it depends on how near-parabolic and hyperbolic orbits are treated.

 

 

 

 

With a Tisserand value relative to Jupiter of –0.35, this is a Halley-type comet orbit (Tancredi, 2014; T_J = –0.01 and P = 19.8 years for the radiant method, T_J = –0.35 and P = 44.7 years for the orbit method). The descending node lies at 13.3 A.U. for the radiant method (between the orbits of Saturn and Uranus) and at 23.1 A.U. for the orbit method (between the orbits of Uranus and Neptune) (Figure 14). With a high eccentricity, the slightest observational or instrumental uncertainty on the velocity results in a huge difference in aphelion. The radiant method identification includes some meteors with smaller heliocentric velocities that result in a mean orbit with a lower eccentricity. The orbit based mean orbit (blue in Figure 14) is probably the best representative orbit for this shower. The meteoroid stream M2026-R1 with its retrograde orbit encounters the Earth orbit at its ascending node close to its perihelion (Figure 15).

 

 

 

A search for a possible parent body based upon the mean orbit of the radiant method did not result in any positive match, the ten best results are listed in Table 2. The D_SH values are between 0.41 and 0.80 for the top ten and none of the candidates passes within 0.05 AU of the Earth’s orbit near Ω = 296°.

Table 2 – Top ten matches of a search for possible parent bodies with D_D < 0.30, based upon the mean orbit derived from the orbit method (Table 1, 2019–2026). JPL ELEMENTS.COMET (2026-10-26).

Name	DD
C/2013 UQ4 (Catalina)	0.160
C/1874 G1 (Winnecke)	0.162
C/2013 A1 (Siding Spring)	0.171
C/1500 H1	0.187
273P/Pons-Gambart	0.188
C/1110 K1	0.200
C/1852 K1 (Chacornac)	0.210
C/2018 N1 (NEOWISE)	0.218
C/1947 S1 (Bester)	0.221
C/2020 R4 (ATLAS)	0.256

 

5  Conclusions

The radiant density maps show a distinct concentration of the M2026-R1 radiant on July 18 in 2026. M2026-R1 was also detected in 2024 and marginally in 2023 at about the 2026 level, so it may be a weak annual shower. Similar orbits were detected with the orbit-based method during about a week and in previous years. Although a distinct concentration is visible in radiant positions, the diagrams with the orbital elements i versus Π, e versus Π, e versus i show a relatively large spread which comes mainly from v_g errors near the parabolic limit, while the core radiant is compact (median offset 0.66° for the 15 members with solar longitude 115.0° – 116.2°) and the main activity lasts about one day (λ_ʘ 115.0°–116.2°) each year. Only the perihelion distance q appears as a concentration. M2026-R1 is a barely detectable footprint of a dust remnant of an unknown Halley-type comet. Future observations may reveal whether this activity becomes stronger or drops back below the threshold of detectability. The revised solution (annual activity) will be submitted to the MDC as an additional solution of M2026-R1.

Acknowledgments

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 927 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 2025 annual report (Roggemans et al., 2026b). The following 160 cameras contributed to paired meteors by either of the two methods used in this study:

AU0003, AU000D, AU000F, AU000U, AU000V, AU000W, AU000Z, AU001A, AU001B, AU001Q, AU001U, AU002B, AU0038, AU0039, AU004L, AU004Q, BR000F, BR000J, BR000Q, BR000S, BR0013, BR001H, BR001W, BR002C, CZ000Q, CZ000R, ES0019, ES001H, HR0002, HR000S, HR001Z, HR0027, HR002J, HR002X, HU0001, HU0003, HU0009, HU000B, HU000F, KR0016, KR001P, KR001Z, KR002C, MX0001, MX0003, NZ0001, NZ0003, NZ0004, NZ0007, NZ000M, NZ000N, NZ000Q, NZ000W, NZ000Z, NZ0012, NZ0014, NZ0017, NZ0018, NZ001H, NZ001Q, NZ001R, NZ001S, NZ001V, NZ001Z, NZ0020, NZ0022, NZ0023, NZ0025, NZ0026, NZ0027, NZ002A, NZ002C, NZ002D, NZ002E, NZ002H, NZ002J, NZ002K, NZ002L, NZ002N, NZ002P, NZ002R, NZ002S, NZ002U, NZ002W, NZ002X, NZ002Y, NZ0030, NZ0033, NZ0034, NZ0035, NZ0036, NZ0037, NZ0038, NZ003A, NZ003B, NZ003C, NZ003E, NZ003G, NZ003H, NZ003N, NZ003Q, NZ003R, NZ003S, NZ003U, NZ003X, NZ003Y, NZ0040, NZ0042, NZ0044, NZ0045, NZ004A, NZ004D, NZ004H, NZ004L, NZ004N, NZ004S, NZ004T, NZ004V, NZ004X, NZ004Y, NZ0051, NZ0059, NZ005B, NZ005C, NZ005D, NZ005G, NZ005H, NZ005J, NZ005K, NZ005L, NZ005Q, NZ005S, NZ005T, NZ005U, NZ005Y, NZ005Z, NZ0061, NZ0065, NZ0068, NZ006F, NZ006J, NZ006K, NZ006M, NZ006N, NZ006P, NZ006V, NZ0073, NZ007C, NZ007E, PL0008, SK0006, US0004, US0007, US0008, US0009, US003T, US0066, USL006, USL00C and USL00M.

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