By Paul Roggemans and Carl Johannink
Abstract: The United Arab Emirates Camera Network, UACN, registered a significant number of Ursid orbits during the night of 22-23 December 2019 between 20h00m and 02h00m UT. The CAMS-BeneLux network struggled with poor weather circumstances but still registered three Ursid orbits, when the sky conditions improved after 2h UT, the number of Ursid orbits had decreased. The question arises if the Ursids should remain on the short list of annual major showers since the activity is comparable or inferior to several established minor showers. A -1 Ursid meteor recorded with RMS cameras allowed to calculate its orbit with three different orbit software solutions which resulted in three similar but nevertheless not identical orbits.
1 Introduction
The Ursid meteor stream is being listed since long time as one of the annual major showers. However, anyone who made attempts to observe this shower has been disappointed unless being lucky to observe during one of the outbursts of the Ursids. Most of the time low numbers of Ursid meteors are registered, not at all at the level of any of the major showers. The question arises if the Ursids should be rather qualified as a minor shower that may produce outbursts? Listing the Ursids as an annual major shower raises expectations that are most of the time not fulfilled. This is a good topic for a future case study.
Figure 1 – Radiant map of CAMS for 2019 December 23 with the radiants of 46 Ursid orbits .
2 The Ursids in 2019
The United Arab Emirates Camera Network, UACN, registered a significant Ursid activity during the night of December 22–23. They collected a nice set of orbits during the time interval of 270.40° < λʘ < 270.65°, corresponding to December 22–23, at about 20h00m–02h00m UT.
Table 1 – Number of orbits collected by CAMS worldwide in 2019 for the Ursids (URS#015). Hydrids (HYD#016), December Monocerotids (MON#019) and the December Comae Berenicids (COM#020). The time period covers the complete Ursids activity period.
| Night | URS | HYD | MON | COM |
| December 11–12 | 1 | 48 | 28 | 12 |
| December 12–13 | 2 | 64 | 34 | 18 |
| December 13–14 | 2 | 47 | 37 | 16 |
| December 14–15 | 1 | 56 | 32 | 29 |
| December 15–16 | 2 | 49 | 37 | 62 |
| December 16–17 | 3 | 29 | 11 | 27 |
| December 17–18 | 3 | 30 | 14 | 31 |
| December 18–19 | 11 | 63 | 11 | 66 |
| December 19–20 | 10 | 57 | 16 | 62 |
| December 20–21 | 17 | 21 | 2 | 39 |
| December 21–22 | 13 | 23 | 4 | 27 |
| December 22–23 | 46 | 20 | 1 | 24 |
| December 23–24 | 3 | 11 | 3 | 29 |
| December 24–25 | 2 | 9 | 1 | 30 |
The numbers of Ursid orbits depend upon the weather circumstances across the camera networks, but these numbers are very low. In Table 1 we list the number of Ursid orbits registered by all CAMS networks together for each night. The first Ursid orbit was registered during the night December 11–12, the last one December 24–25, the sharp maximum occurred in the night of December 22–23 at about λʘ = 270.52°.
Table 1 also lists the number of orbits registered for three established minor showers: the sigma Hydrids (HYD#016), the December Monocerotids (MON#019) and the December Comae Berenicids (COM#020). If these are typical minor showers, then what are the Ursids?
2 Ursids by CAMS BeNeLux
Unfortunately, the CAMS BeNeLux region remained overcast at most places in the evening hours that night. Only three meteors, all Ursids, were collected before 2h UT: one at 20h14m UT, one at 21h13m UT and another at 00h24m UT. No dust trails were expected to produce any enhanced activity in 2019.
Between 2h00m–3h00m UT two orbits were registered, once again both Ursids (02h29m and 02h46m UT). After 03h00m UT more and more regions in the BeNeLux got clear sky, but unfortunately the Ursid activity seemed to have weakened. Until twilight, another 31 meteor orbits were collected, including only 5 Ursids, even though the radiant was located higher in the sky.
Figure 2 – The –1 magnitude Ursid meteor of 2019 December 23, 06h06m05.95s, registered by BE0003 (3815) at Cosmodrome, Genk, Belgium. RMS camera with f/0.95,3.6 mm lens (Adriana and Paul Roggemans).
Figure 3 – The –1 magnitude Ursid meteor of 2019 December 23, 06h06m05.95s, registered by BE0004 (3831) at Mechelen, Belgium. RMS camera with f/1.0,8 mm lens lens (Adriana and Paul Roggemans).
The orbital elements for all ten Ursids are listed in Table 3. The mean orbit (Jopek et al., 2006) was calculated using all these orbits except the Ursid registered at 06h24m which has a too high geocentric velocity. The result is shown in Table 2 and compared with a reference from literature.
Table 2 – Mean orbit for 9 CAMS BeNeLux orbits compared to a reference orbit from literature.
| Mean orbit CAMS BeNeLux |
Jenniskens et al.
2016 |
|
| λʘ | 270.7° | 271.0° |
| αg | 218.5° | 219.9° |
| δg | +75.2° | +75.4° |
| vg | 33.1 km/s | 32.9 km/s |
| a | 4.84 A.U. | 4.87 A.U. |
| q | 0.938 A.U. | 0.940 A.U. |
| e | 0.806 | 0.807 |
| ω | 206.0° | 205.6° |
| Ω | 270.6° | 270.1° |
| i | 53.0° | 52.6° |
The Ursid of December 23, 06h06m UT was recorded by two RMS cameras (see Figure 2 and 3). The orbits calculated by CAMS software are marked with ‘C’ in Table 3. The RMS camera data has also been analyzed by Denis Vida for the Global Meteor Network and since the RMS cameras provide also the detection info in UFO Capture format, Takashi Sekiguchi could compute the orbit with the UFO_orbit software of SonotaCo. This offers a unique possibility to compare the computational result for the orbit obtained by three different software solutions, based on identical measured positional data.
The results can be compared in Table 3 with the three last mentioned orbits obtained for the same Ursid meteor, computed by Carl Johannink (C), by Denis Vida (G) and by Takashi Sekiguchi (S). The CAMS software and the SonotaCo software are well established, while the Global Meteor Network software is still being finetuned. SonotaCo uses only the position of the begin and end points of the meteor to compute the trajectory solution and the orbit. CAMS and GMN use all the measured positions on the meteor trail and take the deceleration into account.
The three solutions result in three similar orbits, but these orbits are not identical. CAMS gives the highest geocentric velocity vg, eccentricity e, inclination i, and the lowest argument of perihelion ω. The GMN solution has the begin point He more than a kilometer lower in the atmosphere than CAMS, although the measured position used is identical.
These results provide us with an idea to which extent the method used to compute the orbit produces a slightly different result. The differences are larger than the error margins given and should be explained somehow. When the orbits depend so much on the method used to compute them, the resulting mean orbits that serve as references will also be different from each other. Another question arises as how many digits behind the comma are relevant to be listed for orbital elements?
Table 3 – The 10 orbits as obtained by CAMS BeNeLux (calculated by Carl Johannink). The Ursid of 2019 Dec. 23, 06h06m06s UT, registered by BE0003 (003815) and BE0004 (003831), has also the orbit obtained for the Global Meteor Network (calculated by Denis Vida) and computed with the UFO_orbit software of SonotaCo (calculated by Takashi Sekiguchi).
| C 2019/12/22 20h14m10.28s |
C 2019/12/22
21h13m22.29s |
C 2019/12/23
00h24m33.28s |
C 2019/12/23
02h29m52.41s |
|
| λʘ | 270.407° | 270.449° | 270.584° | 270.673° |
| αg | 217.42 ± 0.004° | 214.29 ± 0.00° | 215.12 ± 2.17° | 217.68 ± 1.64° |
| δg | +75.34 ± 0.005° | +75.21 ± 0.00° | +75.63 ± 1.38° | +74.31 ± 0.48° |
| vg | 33.64 ± 0.00 km/s | 33.10 ± 0.00 km/s | 34.74 ± 0.21 km/s | 33.29 ± 0.27 km/s |
| Hb | 107.33 ± 0.00 km | 104.53 ± 0.00 km | 98.98 ± 0.02 km | 101.35 ± 0.03 km |
| He | 70.66 ± 0.01 km | 92.31 ± 0.00 km | 88.32 ± 0.07 km | 91.50 ± 0.05 km |
| a | 5.58 A.U. | 4.27 A.U. | 8.92 A.U. | 4.37 A.U. |
| q | 0.93778 ± 0.00001 A.U. | 0.93267 ± 0.000 A.U. | 0.93416 ± 0.0043 A.U. | 0.94028 ± 0.00261 A.U. |
| e | 0.8319 ± 0.0002 | 0.7814 ± 0.0000 | 0.8953 ± 0.0481 | 0.7850 ± 0.0248 |
| ω | 206.206 ± 0.003° | 208.15 ± 0.00° | 206.70 ± 1.11° | 205.889 ± 0.890° |
| Ω | 270.4048 ± 0.0000° | 270.4470 ± 0.0000° | 270.5835 ± 0.0002° | 270.6729 ± 0.0001° |
| i | 53.54 ± 0.004° | 53.22 ± 0.00° | 54.63 ± 0.81° | 53.65 ± 0.40° |
| C 2019/12/23 02h46m03.34s |
C 2019/12/23 03h15m47.48s |
C 2019/12/23 04h45m31.94s |
C 2019/12/23 06h24m01.37s |
|
| λʘ | 270.684° | 270.705° | 270.769° | 270.839° |
| αg | 219.17 ± 2.03° | 219.16 ± 1.24° | 225.41 ± 0.46° | 214.28 ± 0.80° |
| δg | +75.40 ± 1.63° | +75.13 ± 0.20° | +76.17 ± 0.21° | +74.91 ± 0.74° |
| vg | 33.14 ± 0.11 km/s | 30.31 ± 0.15 km/s | 32.84 ± 0.08 km/s | 40.72 ± 0.18 km/s |
| Hb | 98.86 ± 0.04 km | 100.19 ± 0.02 km | 99.73 ± 0.04 km | 101.95 ± 0.04 km |
| He | 89.33 ± 0.04 km | 84.23 ± 0.09 km | 90.34 ± 0.05 km | 92.19 ± 0.04 km |
| a | 5.12 A.U. | 2.72 A.U. | 6.62 A.U. | ꝏ A.U. |
| q | 0.93975 ± 0.00507 A.U. | 0.93850 ± 0.00165 A.U. | 0.94558 ± 0.0058 A.U. | 0.93746 ± 0.00210 A.U. |
| e | 0.8163 ± 0.0490 | 0.6548 ± 0.0126 | 0.8571 ± 0.0087 | 1.2665 ± 0.0311 |
| ω | 205.762 ± 1.310° | 207.882 ± 0.647° | 203.638 ± 0.18° | 203.659 ± 0.480° |
| Ω | 270.6844 ± 0.0000° | 270.7056 ± 0.0001° | 270.7695 ± 0.0000° | 270.8396 ± 0.0002° |
| i | 52.82 ± 0.83° | 49.82 ± 0.23° | 51.69 ± 0.14° | 60.58 ± 0.49° |
| C 2019/12/23 06h34m57.17s |
C 2019/12/23 06h06m05.95s CAMS |
G 2019/12/23 06h06m08.21s GMN |
S 2019/12/23 06h08m08s SonotaCo |
|
| λʘ | 270.846° | 270.826° | 270.826° | 270.826° |
| αg | 219.88 ± 0.51° | 218.50 ± 0.87° | 218.07 ± 0.17° | 218.56° |
| δg | +75.07 ± 0.38° | +74.11 ± 0.47° | +75.10 ± 0.30° | +74.87° |
| vg | 32.82 ± 0.11 km/s | 34.21 ± 0.42 km/s | 33.46 ± 0.04 km/s | 33.27 km/s |
| Hb | 100.59 ± 0.03 km | 104.95 ± 0.05 km | 103.76 ± 0.04 km | 104.57 km |
| He | 87.37 ± 0.03 km | 81.86 ± 0.08 km | 81.10 ± 0.03 km | 81.80 km |
| a | 4.57 A.U. | 5.83 A.U. | 5.26 ± 0.15 A.U. | 4.87 A.U. |
| q | 0.94130 ± 0.00110 A.U. | 0.94249 ± 0.00049 A.U. | 0.938929±0.0009 A.U. | 0.940104 A.U. |
| e | 0.7942 ± 0.0135 | 0.8384 ± 0.0286 | 0.8215 ± 0.0055 | 0.806835° |
| ω | 205.480 ± 0.302° | 204.74 ± 0.31° | 205.95 ± 0.24° | 205.73° |
| Ω | 270.8472 ± 0.0001° | 270.8268 ± 0.0004° | 270.8268 ± 0.0000° | 270.8258° |
| i | 52.59 ± 0.23° | 54.64 ± 0.57° | 53.37 ± 0.19° | 53.26° |
3 Conclusion
The Ursids displayed a fair level of activity during about 6 hours in the night of 2019 December 22–23, 20h to 2h UT, but the number of orbits recorded for the Ursids remains rather modest compared to the numbers recorded for some minor showers that are active at the same time. The question arises if the Ursids should remain listed as an annual major shower, or be rather considered as a minor shower with periodic outbursts?
Computation of the orbit for an identical Ursid meteor using the CAMS software, the GMN software and the SonotaCo software results in similar but not identical orbits. The question if and to which extent orbits may differ depending on the software used requires further investigation.
Acknowledgement
The authors wish to thank Denis Vida for providing the GMN results and the Py program to compute average orbits according to the method of Jopek et al. (2006). We thank Takashi Sekiguchi for his computations with the SonotaCo software and Masahiro Koseki for his mediation.
Thanks to the CAMS BeNeLux team that provided the meteor video data for December 2019: Hans Betlem (Leiden, Netherlands, CAMS 371, 372 and 373), Jean-Marie Biets (Wilderen, Belgium, CAMS 379, 380, 381 and 382), Martin Breukers (Hengelo, Netherlands, CAMS 320, 321, 322, 323, 324, 325, 326 and 327, RMS 328 and 329), Guiseppe Canonaco (Genk, RMS 3815), Bart Dessoy (Zoersel, Belgium, CAMS 397, 398, 804, 805, 806 and 888), Jean-Paul Dumoulin and Christian Walin (Grapfontaine, Belgium, CAMS 814 and 815, RMS 003814), Luc Gobin (Mechelen, Belgium, CAMS 390, 391, 807 and 808), Tioga Gulon (Nancy, France, CAMS 3900 and 3901), Robert Haas (Alphen aan de Rijn, Netherlands, CAMS 3360, 3361, 3362, 3363, 3364, 3365, 3366 and 3367), Robert Haas (Texel, Netherlands, CAMS 810, 811, 812 and 813), Robert Haas / Edwin van Dijk (Burlage, Germany, CAMS 801, 802, 821 and 822), Klaas Jobse (Oostkapelle, Netherlands, CAMS 3030, 3031, 3032, 3033, 3034, 3037, 3038 and 3039), Carl Johannink (Gronau, Germany, CAMS 311, 312, 314, 315 and 316), Hervé Lamy (Dourbes, Belgium, CAMS 394 and 395), Hervé Lamy (Humain Belgium, CAMS 816), Hervé Lamy (Ukkel, Belgium, CAMS 393), Koen Miskotte (Ermelo, Netherlands, CAMS 351, 352, 353 and 354), Tim Polfliet (Gent, Belgium, CAMS 396), Steve Rau (Zillebeke, Belgium, CAMS 3850 and 3852), Paul and Adriana Roggemans (Mechelen, Belgium, CAMS 383, 384, 388, 389, 399 and 809, RMS 003830 and 003831), Hans Schremmer (Niederkruechten, Germany, CAMS 803) and Erwin van Ballegoij (Heesch, Netherlands,CAMS 347 and 348).
References
Jenniskens P., Nénon Q., Albers J., Gural P. S., Haberman B., Holman D., Morales R., Grigsby B. J., Samuels D. and Johannink C. (2016). “The established meteor showers as observed by CAMS”. Icarus, 266, 331–354.
Jopek T. J., Rudawska R. and Pretka-Ziomek H. (2006). “Calculation of the mean orbit of a meteoroid stream”. Monthly Notices of the Royal Astronomical Society, 371, 1367–1372.
