Abstract: In September 2020, activity of a newly listed shower called the September upsilon Taurids (IAU #1045, code SUT) was detected by the CAMS and GMN video camera networks. This appears to have been an outburst, which means that this meteor shower has irregular activity. Reports of visual meteor activity emanating from Taurus during September were first mentioned in the early 1990s, while later reports talked about ‘September Taurids’. This paper examines the visual observation history, reports on the new video observations in 2020, examines possible evidence of activity in previous year’s CAMS data, and discusses the concomitant activity in the vicinity which may have influenced earlier visual observations.
1 Past reports of visual activity
Members of the Dutch Meteor Society (DMS) first reported the possibility of a radiant in Taurus during September as early as 1991 (Jenniskens, 1992). Koen Miskotte observed a number of fast meteors on the nights of September 11–12 and 13–14. Peter Jenniskens observed on September 15 for 1.5 hours, seeing several fast meteors from Taurus, as well as activity on the three subsequent nights. Plots of the observed meteors gave a radiant about RA = 76°, Decl. = +19°, shown as +1 in Figure 1, which also shows the positions of other observed centers of activity determined by plotting, as well as radiant positions of known meteor showers listed in the IAU Meteor Data Centre (MDC) list of all showers (Jopek and Rudawska, 2020. List of all meteor showers, IAU Meteor Data Centre, updated 2020 September 27, available at https://www.ta3.sk/IAUC22DB/MDC2007/).
The shower was also reported in later years. Robert Lunsford observed visual activity on the night of 1996 September 10–11 (O’Meara, 2004), and was confirmed the following night by George Gliba and Norman McLeod (Gliba, 2002). On 1996 September 11–12 McLeod observed weak activity from two possible radiants, determined as RA = 48°, Decl. = +18° and RA = 58.5°, Decl. = +16°, shown as +2 and +3 in Figure 1. McLeod also observed five fast-moving meteors between September 18, 06h26m and 09h26m UT from a radiant at RA = 63°, Decl. = +17.5° (Figure 1, +4).
Olech (2003), however, did not find the shower during an investigation of its existence using data from the Polish Visual Meteor Database (PVMD) during the period September 5–25, for the years 1996–2000. Based on observations by 25 observers totaling nearly 400 hours he concluded there was no trace of activity from the September Taurids and therefore no evidence to support the existence of the stream.
Figure 1 – Observed radiant positions determined by plotting (white + symbols) referred to in Table 1, and known radiant positions (coloured symbols) of meteor showers listed in Table 3. Plotted positions are from: 1 = DMS 1991, 2 = McLeod 1996a, 3 = McLeod 1996b, 4 = McLeod 1996c, 5 = O’Meara 2001, 6 = Velkov 2002, 7 = Streicher 2004, 8 = Cooper 2004. Positions are as reported and have not been adjusted for zenith attraction. SUT radiant position with yellow symbol is that derived from 2020 data for solar longitude 179.2° (2020 September 21.9). OTA#896, PTA#556, NUE#337 and UCE#194 with yellow symbols are approximate positions of the radiant at λʘ = 179° allowing for radiant drift from date of their listed maxima in Table 3. The radiants for NUE are as Table 3; NUE1 = Jenniskens et al. (2016) and NUE3 = SonotaCo (2009). That for NUE2 (Molau and Rendtel, 2009) is outside below the map. Cyan symbols show the positions for SUT and OTA for λʘ =172° assuming a radiant drift of 1°/day eastwards parallel to the ecliptic. Green circle is the radiant location of 6 meteors logged by CAMS on 2019 September 17 as 130 Taurids (OTA#896), and was possibly an outburst of that shower.
There were several reports of the stream reappearing in 2001. Stephen O’Meara (2002) observed from Hawaii on September 14, seeing six meteors between 13h35m–13h47m UT, and a further four during casual observations up to 14h14m UT. The meteors radiated from a point between the Hyades and Pleaides clusters. He followed up with a dedicated watch on September 15, seeing six members between 13h30m–14h30m UT, and a further seven between 14h30m–15h30m UT. He estimated the radiant as RA = 60°, Decl. = +22° (Figure 1, +5). All members were fast-moving. Lorna McCalman (O’Meara, 2004) observing from the Isle of Bute, saw twenty-five meteors in 3.5 hours on the night of September 15–16, confirming significant activity from the stream extended at about the same rate over a period of at least two nights. However, Alastair McBeath (2002) reporting on Society for Popular Astronomy (SPA) observations said “Several of our visual watchers were active during this spell in 2001, although not on September 14–15 or 15–16, but plots made on other nights around these do not confirm a radiant between the Hyades and Pleiades”.
A number of further observations were made in 2002. Streicher observed six possible members on the morning of September 14 between 01h00m–02h30m UT, all reportedly fast-moving. Gliba observed six meteors between 04h00m–07h00m UT on September 14 (O’Meara, 2004). O’Meara observed between September 14, 12h22m–15h22m UT, seeing thirteen members from 12h22m–13h22m UT (all magnitude +4 or fainter), eleven from 13h22m–14h22m UT, and four members between 14h22m–15h22m. The majority of all observed September Taurids were magnitude +3 or fainter. Valentin Velkov (2003, 2021) reported observations by himself and Eva Bojurova from Bulgaria, where activity was seen on the night of 2002 September 14–15. From thirty-five plotted meteors, nine possible September Taurids were plotted from a radiant with diameter about 10° and centred at RA = 61°, Decl. = +21° (Figure 1, +6). All members were fast moving. Streicher also observed on September 15 between 02h00m–02h20m UT, but only observed two possible members under partly cloudy skies.
During 2004 Magda Streicher and Tim Cooper observed on the mornings of September 12–14, seeing weak activity on all three dates, and highest activity on the morning of September 12, with three September Taurids for both observing independently in 2.0 hours. The combined total for both observers was twelve September Taurids from seventy-one meteors in 8.5 hours observation. All meteors seen were plotted, and the derived radiant positions were 71.2°, +19.3° (Cooper, +7) and 63.7°, +19.3° (Streicher, +8).
A summary of all visual observations for the years 1996–2004 is given in Table 1. After 2004, the shower unfortunately appears to have been neglected, but with the advent of CAMS in 2011 (Jenniskens et al., 2011) a permanent record of activity now exists which can be examined for possible activity in more recent years.
Table 1 – Summary of possible September Taurid visual observations 1991–2004.
| Date | Date, Time UT | Solar long. λʘ(°) | N | Teff (h) | Radiant (°) | Observer |
| 1991 | Sep 11–12 | 168.9 | Miskotte | |||
| 1991 | Sep 13–14 | 170.8 | Miskotte | |||
| 1991 | Sep 15 | 171.8 | 1.5 | 76, +19 | Jenniskens | |
| 1996 | Sep 10–11 | 168.3 | Lunsford | |||
| 1996 | Sep 11–12 | 169.3 | Gliba | |||
| 1996 | Sep 11–12 | 169.3 | 5 | 48, +18; 58.5, +16 | McLeod | |
| 1996 | Sep 18, 0626–0926 | 175.67–175.79 | 5 | 3.0 | 63, +17.5 | McLeod |
| 2001 | Sep 14, 1335–1414 | 171.79–171.81 | 10 | 0.65 | O’Meara | |
| 2001 | Sep 15, 1330–1530 | 172.76–172.84 | 13 | 2.0 | 60, +22 | O’Meara |
| 2001 | Sep 15–16 | 173.2 | 25 | 3.5 | McCalman | |
| 2002 | Sep 14, 0100–0230 | 171.03–171.09 | 6 | 1.5 | Streicher | |
| 2002 | Sep 14, 0400–0700 | 171.15–171.27 | 6 | 3.0 | Gliba | |
| 2002 | Sep 14, 1222–1522 | 171.49–171.61 | 28 | 3.0 | O’Meara | |
| 2002 | Sep 14–15 | 172.0 | 9 | 61, +21 | Velkov | |
| 2002 | Sep 15, 0200–0220 | 172.04–172.06 | 2 | 0.3 | Streicher | |
| 2004 | Sep 12, 0030–0235 | 169.53–169.62 | 3 | 2.0 | 63.7, +19.3 | Streicher |
| 2004 | Sep 12, 0030–0235 | 169.53–169.62 | 4 | 2.0 | 71.2, +19.3 | Cooper |
| 2004 | Sep 13, 0100–0300 | 170.52–170.61 | 2 | 2.0 | 63.7, +19.3 | Streicher |
| 2004 | Sep 14, 0112–0212 | 171.51–171.55 | 2 | 1.0 | 71.2, +19.3 | Cooper |
| 2004 | Sep 14 | 171.5 | 1 | 63.7, +19.3 | Streicher | |
| 2020 | Sep 21–22, 2220–0040 | 179.1–179.2 | 14 | 66.0, +24.1 | CAMS | |
| 2020 | Sep 21–22, 1950–0040 | 179.0–179.2 | 18 | GMN |
Notes: column N gives the number of meteors reported in time Teff hours. CAMS and GMN video data used for confirmation are given as comparison.
Table 2 – Radiant position, peak activity and orbital details for September upsilon Taurids (SUT, #1045).
| Radiant – RA (J2000) (°) | 66.0 ± 1.2 |
| Radiant – Decl. (°) | +24.1 ± 0.6 |
| Peak activity – solar longitude λʘ (°) | 179.15 ± 0.04 |
| Duration – FWHM solar longitude (°) | 0.14 |
| Geocentric velocity – vg km/s | 67.8 ± 1.2 |
| Perihelion distance – q AU | 0.654 ± 0.007 |
| Eccentricity – e | 0.992 ± 0.015 |
| Inclination – i (°) | 174.9 ± 0.3 |
| Argument of perihelion – ω (°) | 252.7 ± 0.9 |
| Longitude of ascending node – Ω (°, J2000.0) | 179.15 ± 0.13 |
Table 3 – Showers with radiants in the vicinity of Taurus and active at the same time as the September upsilon Taurids.
| Shower code | IAU # | Year | RA (°) |
Decl. (°) |
ΔRA (°) |
ΔDec (°) |
vg km/s |
λʘ (°) Max. |
| SUT | 1045 | 2020 | 66.2 | +24.1 | 67.8 | 179.2 | ||
| OTA | 896 | 2018 | 86.5 | +17.9 | 72.4 | 179.3 | ||
| PTA | 556 | 2014 | 63.9 | +29.1 | 1.15 | 0.20 | 60.2 | 193 |
| NUE(1)
NUE(2) NUE(3) |
337
|
2008
|
61.5
74.7 68.7 |
+4.3
+0.3 +1.1 |
0.95
0.6 0.14 |
0.19
-1.9 -0.13 |
67.1
67.0 65.9 |
163.0
165 167.9 |
| UCE | 194 | 1999 | 38.6 | -2.8 | 61.0 | 146.0 |
Notes: SUT = September upsilon Taurids, OTA = 130 Taurids, PTA = phi Taurids, NUE = nu Eridanids and UCE = upsilon Cetids. Year is that for which the shower is first referenced in the IAU MDC list. Data for NUE is from (1) = Jenniskens et al. (2016), 2 = Molau and Rendtel (2009), 3 = SonotaCo (2009). ΔRA and ΔDec are radiant drift from Jopek and Rudawska (2020).
Table 4 – List of confirmed and possible outbursts of September upsilon Taurids.
| Year | Date, September | Solar longitude (°) | Type |
| 1991 | 11–15 | 168–172 | Visual |
| 1996 | 11–13 | 169–171 | Visual |
| 2001 | 15–16 | 172–173 | Visual |
| 2002 | 14 | 171 | Visual |
| 2014 | 23 | 180 | Video |
| 2017 | 22 | 179 | Video |
| 2019 | 10, 22–23 | 167, 178–179 | Video |
| 2020 | 22 | 179.15 | Video |
2 The 2020 activity and confirmation of the shower
CAMS radiant plots for the period 2020 September 10–25 are shown in Figures 2a and 2b. The first possible detections by the CAMS network were on the night of September 22 (Cooper, 2020) when the author mailed Dr. Jenniskens “could you check similarities of the bunch just north of Taurus in data for September 22 please? Location is approx. RA = 66 deg, Dec = +23.8 deg, v = approx. 68 km/s.” That activity can be seen in Figure 2b lower left panel, as a tight bunching of points immediately north of the Hyades.
Closer examination of Figure 2b shows the shower may have been active one day either side of this date, but at reduced rates. In total fourteen shower members were detected (Jenniskens and Cooper, 2020), seven by CAMS Namibia, six by the United Arab Emirates Astronomical Camera Network, and one by CAMS Florida. Unfortunately, CAMS South Africa was clouded out. Nine meteors occurred between solar longitudes λʘ = 179.13–179.24°, corresponding to September 21.959 to 22.071 UT. In addition, eighteen members were detected by cameras operated by the Global Meteor Network (GMN), with peak between λʘ = 179.05 and 179.24°, corresponding to September 21.876 to 22.071 UT.
Figure 2a – Radiant plots from CAMS global data for 2020 September 10–17. Black dots are stars, white dots are either sporadic meteors or radiants not in the CAMS lookup table, red dots at the bottom of each frame are identified as nu Eridanids (NUE, #337), orange dots to their right (west) are upsilon Cetids (UCE, #194).
Figure 2b – Radiant plots from CAMS global data for 2020 September 18–25. Identities as Figure 2a, but in addition red dots on extreme left of frames are 130 Taurids (OTA, #896) and orange dots upper right are phi Taurids (PTA, #556). Concentrations of September upsilon Taurids for September 21 and 22 are clearly visible above the Hyades.
Based on these detections an outburst was announced (Jenniskens and Cooper, 2020), and the shower now becomes known in the IAU MDC Working List of Meteor Showers (Jopek and Rudawska, 2020) as the September upsilon Taurids (SUT, #1045). Derived properties of the meteor stream, including radiant position, peak activity and orbital details are shown in Table 2. The orbit is that of an as-yet unknown long period comet in a low inclination orbit. September upsilon Taurid meteors are fast moving, with geocentric velocity 67.8 km/sec.
3 Evidence of previous activity detected by CAMS and other video networks
Following the outburst in 2020, the author examined CAMS plots for similar concentrations during the period September 10–25 from 2015 onwards. Dates for which possible activity exist are shown in Figure 3. The summary of historical observations of meteors emanating from the vicinity of the Hyades and Pleiades clusters in Taurus is given in Table 4.
There is evidence of a close association of radiants at similar position to the 2020 activity on three nights in the past; 2014 September 23, 2017 September 22 and 2019 September 10. In all three cases activity was absent one day either side of these dates. There was also possible weak activity on the night of 2019 September 22, and this may have continued over into the following night also. Outside these dates, no instances were found of September upsilon Taurid rates exceeding the sporadic background during the years 2014–2019. The increasing number of points in the plots do not reflect increasing meteor activity, but rather an increase in the number of cameras operating as part of the CAMS network.
There is no evidence for September upsilon Taurid activity in CAMS plots prior to 2014, although it should be noted that far fewer data points exist due to the aforementioned fewer operating cameras, with only 60 cameras in 2011, growing to around 530 cameras in 2020. The shower was not identified by Molau and Rendtel (2009) based on analysis of more than 10 years observations by the IMO Video Network. The shower was also not detected by SonotaCo (2009) in its catalog based on video observations of around 240000 meteors during 2007–2008.
Figure 3 – Possible previous detections of September upsilon Taurids by CAMS. Upper row shows captures for 2014 September 23, 2017 September 22 and 2019 September 10. Lower row shows plots for the nights of 2019 September 22 and 23, with 2020 September 22 on the right as reference. The white circles are roughly centred on the same position as the 2020 activity.
4 Concomitant activity
There are several other meteor showers active at the same time as the September upsilon Taurids, with radiants in the vicinity of the Hyades and Pleiades clusters, most of which were not known at the time of the first mentioned visual observations cited here. Details are shown in Table 3, which includes the year in which such activity first became known, and radiant positions are identified in Figure 1.
Figure 4 – Possible outburst of 130 Taurids (OTA#896) on 2019 September 21, red dots left of centre. The Hyades cluster is to the centre right, and the Pleiades can be seen just inside top right. The broad swathe of red dots at bottom are nu Eridanids, and to their right the orange dots are upsilon Cetids.
In particular the 130 Taurids (OTA, #896) and phi Taurids (PTA, #556) have their radiants nearby, but slightly east and west of the September upsilon Taurids respectively. Both showers are weak, but often present, and active over a period of several days. The 2019 plots are notable for a probable outburst of 130 Taurids, with the appearance of at least six members on the night of September 21 (Figure 4), and appearing just one night earlier than the weak September upsilon Taurid activity that year (Figure 3 bottom left panel). There was also discernible activity of 130 Taurids on 2017 September 15, preceding the possible September upsilon Taurid activity that year by seven days. Figure 1 also shows the close proximity of the 130 Taurid (OTA) radiant position at solar longitude 172° to the radiant derived by Dutch Meteor Society members at solar longitude 171.8° in 1991, which might have been a further outburst of that shower.
The nu Eridanids (NUE, #337) have their radiant center some 20° south of the September upsilon Taurids, though the actual positions differ according to SonotaCo (2009), Molau and Rendtel (2009) and Jenniskens et al. (2016). The radiant positions are shown in Figure 1. Irrespective, by careful plotting their identity can easily be resolved, although the radiant is rather extended so that some outliers may contaminate plots of September upsilon Taurids. They are active throughout September nights on all years in CAMS data, sometimes at significant rates. Similarly, to their west are to be found the upsilon Cetids (UCE, #194), which show lower rates from a more compact radiant close by the nu Eridanids. While they can easily be differentiated from the September upsilon Taurids, they presumably cannot be separated from the nu Eridanids by visual means.
Taken together, these radiants would make for a complex pattern of visual activity emanating from the vicinity of Taurus during September each year. Like the September upsilon Taurids (vg = 68 km/s), the 130 Taurids (vg = 72 km/s) and nu Eridanids (vg = 67 km/s) have similar apparent speeds. The phi Taurids and upsilon Cetids are only slightly slower. All this requires careful plotting on behalf of the visual observer to make sense of the yearly changes taking place in activity from this region of sky. CAMS does not suffer from this problem, and the membership of a particular shower is established by comparing the orbital details of captured meteors to the current lookup table used by the CAMS software.
5 Conclusions
The existence of the September upsilon Taurids was established in 2020 in data from the CAMS and GMN video networks. These results showed a brief outburst with peak activity on 2020 September 21.92 – 22.02 (λʘ = 179.15°± 0.04°). Past visual records show possible September upsilon Taurid activity during 1991 September 11–15, 1996 September 11–13, 2001 September 15–16, and 2002 September 14. Examination of historical CAMS video data shows probable activity on 2014 September 23, 2017 September 22, 2019 September 10, with a second burst on 2019 September 22, and still perceptible activity on September 23. In most cases the activity is of short duration and confined to one or two nights.
Reports of visual activity are generally one week earlier than the video data, possibly due to bias in the visual observers focusing around the first recorded dates in the 1990s. Outside the mentioned dates activity does not exceed the sporadic background.
There are several concomitant showers with radiants in the near vicinity, and which may have affected visual observations in the past from the area nearby the Hyades and Pleiades clusters. In particular the 130 Taurids have shown activity during most years, most notably during 2019 when rates appear to have been higher than normal. The proximity of the 130 Taurid radiant at λʘ = 172° to the DMS radiant of 1991 at λʘ = 171.8° is noted, and the possibility that the 1991 activity was due to 130 Taurids rather than September upsilon Taurids cannot be discounted. The efficiency of CAMS and other video networks in elucidating complex meteor activity is demonstrated.
Acknowledgements
Thanks to Dr. Peter Jenniskens (NASA Ames Research Centre and SETI Institute, and CAMS Principal Investigator) for information used in this paper. Also, to the camera operators of the global CAMS network, whose data were used for the radiant plots used in this paper. Radiant plots are from the CAMS site. Comments made by Valentin Velkov used in the preparation of this article are greatly appreciated. Data from the Global Meteor Network is released under the CC BY 4.0 license, and is available online. Solar longitudes were calculated using the application SollongCalc by Kristina Veljkovic, University of Belgrade, Serbia.
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