The recent enhanced activity of the June epsilon Ophiuchids (JEO#459) in 2019 June 19 to 24 and the case study on the available video meteor orbits for 2006-2018 provide sufficient evidence to add this shower as an established meteor shower. Annual activity has been registered during each year. The highest numbers of orbits in past years were recorded at solar longitude 87.5°, about 4.5 days earlier than the middle of the time span with enhanced activity recorded in 2019. A number of other minor showers may be associated and form a dispersed complex with the JEO#459 shower. A possible link with the impacting minor planet 2019 MO requires caution and remains to be proven.
Checking regularly the radiant map of the global CAMS project (http://cams.seti.org/FDL/), a remarkable concentration of radiants caught my attention on the nights around 21-22-23 June at the position of the yet unconfirmed minor meteor shower of the June epsilon Ophiuchids (JEO#459).
This shower was first detected in meteor stream searches on video meteor orbits (Rudawska and Jenniskens, 2014; Kornos et al., 2014). The shower was detected again in the CAMS data 2011–2012 (Jenniskens et al., 2016). The number of orbits, 11 was rather low. A new search on the larger CAMS dataset 2011–2016 had a total of 24 similar orbits (Jenniskens et al., 2018). The preliminary CAMS data for 2019 has more JEO#459 orbits than all previous years together. Therefore, it looks appropriate to look-up what we have about this shower from previous years.
The type of orbit with short period and low inclination in the ecliptic is rather tricky to identify with any discrimination criteria because of the dense dust concentration in this part of the Solar System. There are many meteoroids on very similar orbits which are just sporadics.
2 Available orbit data to search
We have the following orbit data collected over 12 years, status as until June 2019, available for our search:
- EDMOND EU+world with 317830 orbits (until 2016). EDMOND collects data from different European networks which altogether operate 311 cameras (Kornos et al., 2014).
- SonotaCo with 284138 orbits (2007–2018). SonotaCo is an amateur video network with over 100 cameras in Japan (SonotaCo, 2009).
- CAMS with 110521 orbits (October 2010 – March 2013), (Jenniskens et al., 2011). For clarity, the CAMS BeNeLux orbits since April 2013 are not included in this dataset because this data is still under embargo.
In total 712489 video meteor orbits are publicly available. Our methodology to detect associated orbits has been explained in a previous case study (Roggemans et al., 2019).
3 A preliminary search
In order to locate the position where a concentration of June epsilon Ophiuchids orbits can be found, we take some sample JEO orbits to determine the range in time, radiant area and velocity interval where we can find these orbits within a low threshold similarity criterion. This results in:
- Time interval: 53° < λʘ < 210°;
- Radiant area: 199° < αg < 267° & –47° < δg < +33°;
- Velocity: 7 km/s < vg < 20 km/s.
The D-criteria that we use are these of Southworth and Hawkins (1963), Drummond (1981) and Jopek (1993) combined. We define five different classes with specific 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.
Table 1– The average values for the preliminary selection of orbits for the four different threshold levels on the D-criteria, compared to a reference orbit from literature for the shower JEO#459.
|Low||Medium low||Medium high||High||Jenniskens et al. (2018)|
In a first approach we calculate the average orbit for this set, using the calculation method explained by Jopek et al. (2006). Table 1 lists the resulting average orbit for each similarity threshold level in our preliminary sample of orbits. Figure 2 shows the huge radiant scatter for these orbits in Sun centered ecliptic coordinates.
Both the time interval and the radiant area are huge, in fact too big to apply our method to locate a concentration of orbits. This type of short period orbits with low inclination near the ecliptic has a high risk to match with sporadic orbits that look similar by chance. Therefore, it is more appropriate to resample the range to search, but based on the high threshold similarity criterion, rather than on the low similarity criterion like done above.
4 Focus on the core of the shower
Sample orbits within the high threshold (DSH < 0.1 & DD < 0.04 & DH < 0.1) occur within the following time interval, radiant position and velocity range:
- Time interval: 78° < λʘ < 102°;
- Radiant area: 236° < αg < 251° & –21° < δg < –1°;
- Velocity: 12 km/s < vg < 16 km/s.
Selecting all orbits that we have for this interval in solar longitude we find 20952 orbits among our 712489 video meteor orbits. Only 121 orbits have the geocentric radiant position and geocentric velocity within the listed range.
Starting our shower search routine on this dataset with 121 orbits just two iterations are necessary to get a reference orbit averaged with the method of Jopek et al. (2006). The results are shown in Table 2. Only two orbits fail in the low threshold criteria.
Table 2– The average values for the final selection of orbits for the five different threshold levels on the D-criteria. The values can be compared to the orbit for the shower JEO#459 from literature listed in Table 1.
|Low||Medium low||Medium high||High||Very High|
Figure 3 shows the radiant plot in Sun centered ecliptic coordinates. Even the high threshold orbits display a large scatter on the radiant positions which is typical for such low velocity shower with this type of orbit. However, the position of the radiant for the averaged orbit of each threshold level are all five at about the same position (marked as triangles in Figure 3). The only significant difference with the orbit from literature is time related in solar longitude, ascending node and argument of perihelion.
The diffuse nature of this kind of radiants makes it difficult to detect any radiant drift. The plots in Sun centered ecliptic coordinates neutralizes the effect of the radiant drift for orbits obtained at a different time in solar longitude. The radiant size has more than 20° in diameter. Figure 4 shows the same plot as Figure 3, but with a color gradient to mark the variation in geocentric velocity. The speed of the JEO meteoroids in Figure 4 is slower at left and faster at right compared to the median value.
If we look at the number of orbits we have available for each year since 2006 in the interval of 78° < λʘ < 102° and the number of JEO#459 orbits in this interval per year, we can conclude from Table 3 that the shower produces annual activity. Because of the small numbers of shower meteors there is no significant statistical variation in activity from year to year. On average 0.6% of all orbits collected during these nights fit the discrimination criteria for association with the JEO#459.
Table 3 – Number of orbits available for each year in the time interval: 78° < λʘ < 102°, and the percentage of JEO#459 orbits.
Table 4 – Number of orbits available for each of the three contributing networks in the time interval: 78° < λʘ < 102°.
|Network||Total number of orbits||JEO orbits||%|
When we look at the total number of available orbits for each of the three main networks we get at about the same percentage of 0.6% for each network (Table 4).
Although the numbers of JEO#459 orbits are rather small, we may try to pinpoint the time with the highest number of JEO#459 orbits as the most likely time of a shower maximum. Figure 5 shows the distribution in time of the number of JEO-orbits collected for each degree in solar longitude during the period 2006 until 2018. Best numbers of orbits were recorded at about λʘ = 87.5° or 2019 June 19.4, 2.5 day before the maximum given in literature (Jenniskens et al., 2018) and 4.7 days earlier than half way the 4 days long outburst of 2019.
Looking at the absolute magnitude of the 119 JEO#459 meteoroids in this case study, the shower was rather deficient in bright meteors with only 13 events with Mabs brighter than –3 with the brightest case Mabs = –4.5. In the past this shower was completely deficient in exceptional bright meteors.
5 The 2019 JEO outburst
Peter Jenniskens (2019) reported the unusual activity of the June epsilon Ophiuchids (JEO#459) between June 19d08h and 26d05h UT. Most activity was recorded between solar longitude 89.3° and 93.3°, centered around 92.1°. In total 88 JEO#459 orbits were collected by CAMS New Zealand (coordinated by J. Baggaley), CAMS South Africa (coordinated by T. Cooper), CAMS BeNeLux (coordinated by C. Johannink), CAMS Florida (coordinated by A. Howell), LO-CAMS in Arizona (coordinated by N. Moskovitz), and CAMS California (coordinated by P. Jenniskens and D. Samuels) (http://cams.seti.org/FDL/). This is an impressive number compared to the 24 orbits collected in the previous CAMS stream search on the data for the years 2011 until 2015. The 2019 CAMS orbits had the following median orbital elements:
- λʘ = 92.11°
- αg = 245.2° ± 1.3°
- δg = –7.4° ± 2.0°
- vg = 14.2 ± 1.1 km/s
- a = 2.69 ± 0.52 AU
- q = 0.885 ± 0.011 AU
- e = 0.671
- ω = 227.3° ± 1.9°
- Ω = 92.2° ± 1.1°
- i = 5.3° ± 0.9°
- N = 88
Also, the NASA fireball network registered enhanced activity of this shower with the ASGARD system with the June epsilon Ophiuchids being responsible for 50% of the fireball detections in the period June 22–24. In total 8 JEO’s with an orbit were collected.
Peter Eschman and Dimitrii Rychkov of the Global Meteor Network also report registration of JEO#459 orbits. Dimitrii Rychkov at the Krasnodar Region, Russia listed 10 JEO#459 orbits recorded between solar longitude 92.75° and 92.9°.
No outburst was noticed by CMOR, but the slow velocity is not very radar friendly and it would require a special analysis to check if even weak activity can be found in the radar data (Brown, 2019).
6 JEO outburst related with impact?
A small asteroid was found by the Atlas Project Survey (https://atlas.fallingstar.com/home.php) on 2019 June 22.40. The Minor Planet Center attributed 2019 MO as official name to this object. Davide Famocchia at JPL mentioned that this object could impact at a position that coincides with the impact of a large bolide on 2019 June 22 at 21h31m54s UT off the South coast of Jamaica as shared on Twitter and Facebook. It is only the 4th case an impacting body has been observed before the actual impact (https://remanzacco.blogspot.com/2019/06/small-asteroid-neocp-a10eom1-impacted.html).
Denis Denisenko pointed the attention to the similarity between the JEO#459 meteor shower and the orbit of the asteroid 2019 MO. The match between the two orbits is not perfect, but this can be explained as the meteor shower appears to be very dispersed.
Looking at the plot of the inclination i versus length of perihelion Π (Figure 6) with different colors for the similarity threshold classes the scatter is obvious, even for the high threshold similarity criteria. Figure 6 also shows the positions for the orbit of the impactor 2019 MO as well as some possible related meteor showers active in this area. The position for 2019 MO is about 12° away from the concentration of JEO orbits. The position for the comet 300P/Catalina (formerly known as 2005 JQ5) is right on top of the concentration of the JEO-orbits. While writing the CBET 4642 text, Dr. Peter Jenniskens noticed that the Jupiter-family comet 300P/Catalina appears to be the parent body of the JEO #459 meteor shower (Jenniskens, 2019).
Figure 7 shows the same plot as Figure 6, but with a color gradient to show the variation in geocentric velocity. The faster particles tend to be at slightly higher inclination with a higher value for the length of perihelion.
A possible physical connection between the impact of 2019 MO and the JEO#459 outburst requires some caution. A cross reference search of the 2019 MO orbit with all orbits listed in the IAU Working List of Meteor showers identifies four other minor showers besides the JEO#459 shower that all fulfil our similarity criteria. The results of this search are listed in Table 5, with the values for the different D-criteria. The similarity criteria only provide us with an idea about the geometric similarity of the orbits, it says nothing about the physical relationship. This provides no evidence that the minor planet is related to any of these showers.
The showers CLI #275 and MSR #278 are both marked as from asteroidal source. The question is rather if there is a physical relationship between all the different sources listed in Table 5? These different minor showers, the impactor 2019 MO and comet 300P/Catalina may be remnants of one and the same parent body. More research is required to confirm or to decline this possibility.
Table 5 – Comparison between the orbit of 2019 MO and the IAU working list of meteor showers for the showers that fulfil our similarity criteria with for each shower the values of DSH, DD and DH with the orbit of 2019 MO as reference orbit.
|Object||λʘ (°)||R.A. (°)||Decl. (°)||vg km/s||a (AU)||q (AU)||e||ω (°)||Ω (°)||i (°)||DSH||DD||DH|
The June epsilon Ophiuchids produced an exceptional level of activity between 2019 June 19 – 24, confirmed by different networks. A search on video meteor orbits of the period 2006 until 2018 confirmed annual activity. The obtained average orbits are in agreement with the published orbital data in literature.
The June epsilon Ophiuchids radiate from a very large scattered radiant area and may be related to a number of other minor showers that where identified, which could be earlier instances of the same meteor shower complex associated with Jupiter-family comet 300P/Catalina. In past years the June epsilon Ophiuchids were rather deficient in exceptional bright events, the brightest event being Mabs = –4.5. A possible connection with the impacting minor planet 2019 MO should be considered with caution as the orbital similarity may be just by chance.
The June epsilon Ophiuchids can be considered as an established meteor shower. The possible relationship with some other nearby meteor showers and the impactor 2019 MO requires further investigations.
The author is very grateful to Jakub Koukal for maintaining EDMOND, to SonotaCo Network (Simultaneously Observed Meteor Data Sets SNM2007–SNM2018), to CAMS (2010–2013) and to all camera operators involved in these camera networks.
I thank Denis Vida for providing me with scripts to plot a color gradient to show the dispersion in velocity and to compute the average orbit according to the method of Jopek et al. (2006). I thank Peter Jenniskens for providing the recent CAMS data published in the CBET and his valuable comments on this paper.
EDMOND (https://fmph.uniba.sk/microsites/daa/daa/veda-a-vyskum/meteory/edmond/) includes: BOAM (Base des Observateurs Amateurs de Meteores, France), CEMeNt (Central European Meteor Network, cross-border network of Czech and Slovak amateur observers), CMN (Croatian Meteor Network or HrvatskaMeteorskaMreza, Croatia), FMA (Fachgruppe Meteorastronomie, Switzerland), HMN (HungarianMeteor Network or Magyar Hullocsillagok Egyesulet, Hungary), IMO VMN (IMO Video Meteor Network), MeteorsUA (Ukraine), IMTN (Italian amateur observers in Italian Meteor and TLE Network, Italy), NEMETODE (Network for Meteor Triangulation and Orbit Determination, United Kingdom), PFN (Polish Fireball Network or Pracownia Komet i Meteorow, PkiM, Poland), Stjerneskud (Danish all-sky fireball cameras network, Denmark), SVMN (Slovak Video Meteor Network, Slovakia), UKMON (UK Meteor Observation Network, United Kingdom).
Brown P. (2019). Private communication.
Drummond J. D. (1981). “A test of comet and meteor shower associations”. Icarus, 45, 545–553.
Jenniskens P., Gural P. S., Grigsby B., Dynneson L., Koop M. and Holman D. (2011). “CAMS: Cameras for Allsky Meteor Surveillance to validate minor meteor showers”. Icarus, 216, 40–61.
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.
Jenniskens P., Baggaley J., Crumpton I., Aldous P., Pokorny P., Janches D., Gural P. S., Samuels D., Albers J., Howell A., Johannink C., Breukers M., Odeh M., Moskovitz N., Collison J. and Ganjuag S. (2018). “A survey of southern hemisphere meteor showers”. Planetary Space Science, 154, 21–29.
Jenniskens P. (2019). “June epsilon Ophiuchid meteors”. CBET 4642.
Jopek T. J. (1993). “Remarks on the meteor orbital similarity D-criterion”. Icarus, 106, 603–607.
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.
Kornoš L., Matlovič P., Rudawska R., Tóth J., Hajduková M. Jr., Koukal J. and Piffl R. (2014). “Confirmation and characterization of IAU temporary meteor showers in EDMOND database”. In Jopek T. J., Rietmeijer F. J. M., Watanabe J., Williams I. P., editors, Proceedings of the Meteoroids 2013 Conference, Poznań, Poland, Aug. 26-30, 2013. A.M. University, pages 225–233.
Roggemans P., Johannink C. and Cambell-Burns P. (2019). “October Ursae Majorids (OCU#333)”. eMetN, 4, 55–64.
Rudawska R., Jenniskens P. (2014). “New meteor showers identifed in the CAMS and SonotaCo meteoroid orbit surveys”. In Jopek T. J., Rietmeijer F. J. M., Watanabe J., Williams I. P., editors, Proceedings of the Meteoroids 2013 Conference, Poznań, Poland, Aug. 26-30, 2013. A.M. University, pages 217–224.
SonotaCo (2009). “A meteor shower catalog based on video observations in 2007-2008”. WGN, Journal of the International Meteor Organization, 37, 55–62.
Southworth R. R. and Hawkins G. S. (1963). “Statistics of meteor streams”. Smithson. Contrib. Astrophys., 7, 261–286.