By AlexandraTerentjeva and Galina Bolgova
Abstract: PF061018 Bukienka, a meteorite dropping fireball which appeared over southern Poland (Olech et al., 2019), was caused by the known tau-Cetid fireball stream (No. 50 in Terentjeva, 1989, 1990). A description of an extraordinary fireball phenomenon is given.
A fireball with a maximum absolute magnitude of –9.7 appeared in the night 2018 October 5–6, at 00h26m51s UT over southern Poland and was observed by ten video stations of the Polish Fireball Network (Olech et al., 2019). The fireball entered the Earth’s atmosphere with a velocity of 18.2 km/s and started at the height of 86.0 km. At a height of 41.5 km the fireball passed over the village of Bukienka, reaching its maximum brightness. The terminal velocity of the fireball was only 4.9 km/s at a height of 30.8 km. The authors reported that because of these conditions there is a chance for a possible meteorite fall of small fragments with a total mass of 100 ± 50 grams. The predicted area of a possible meteorite impact has been computed. The authors published the orbital elements of this PF061018 Bukienka fireball.
Usually, the fragmentation of the meteoroid body takes place in the lower atmospheric layers, in the region with strong deceleration, where the atmospheric drag and, hence, disruptive forces reach maximum values (Astapovich, 1958). Thus, meteorite droppings are usually caused by the fragmentation of a meteoroid body in the atmosphere. However, there may be meteorite falls produced by a meteoroid stream that initially enters the atmosphere as a cluster of bodies. I. S. Astapovich gives a geometric criterion allowing one to distinguish between these two types.
2 Research results
From a study of the catalogues with orbital elements of fireball and meteoroid streams, we have deduced that the Bukienka meteorite dropping fireball is related to the already known large fireball stream of the τ–Cetids active during the period September 28 – November 26 (No. 50 in Terentjeva, 1989, 1990). The fireball over the Amur river on 1982 October 7 appeared during this activity period. All the data are presented in Table 1.
In the catalogues of 359 minor meteor streams (Terentjeva, 1963, 1966, 1967 and 1968) no minor streams exist associated with the Bukienka fireball.
The orbital elements of the Bukienka fireball are in a good agreement with the orbital elements of the τ-Cetids fireball stream. The difference in the value of the major semi-axis is not a big problem, since large, and especially dispersed streams always contain both long- and short-period orbits. The τ-Cetids are such a wide spread stream and the Earth needs two months approximately to cross this shower.
If we apply the widely used criterion for the determination of stream membership proposed by R. B. Southworth and G. S. Hawkins, then for two orbits (see Table 1) we obtain a value of DSH = 0.16, which is quite appropriate for such a wide stream as the τ-Сetids (and a large number of streams alike). For major streams such as the Orionids and the Perseids DSH ranges from 0.00 to 0.24 and more (Southworth and Hawkins, 1963).
Nevertheless, we should note that there are no universal mathematical criteria. Not any criterion can take into account the whole range of orbits, individual properties and peculiarities of meteor showers and streams. The used criteria give inappropriate results for the streams, whose orbits are close to ecliptic, streams with N, S and Q branches, most of wide streams, etc. As Prof. Astapovich once said, one cannot push the vast variety of phenomena into limits of formal mathematical criterion. Thus, requiring DSH to be less than 0.1 for all streams in the Solar System is incorrect. Mathematical criteria while searching, of course, help to find required orbits, though these play a subsidiary role. The main role belongs to common sense. The fireball stream of the τ-Cetids fits in the list of meteorite-producing fireball streams, found by the authors (Terentjeva and Barabanov, 2017, 2018, 2019).
This list should be permanently expanded because meteorite-producing streams are of great importance. In particular, these streams may be hazardous for Earth. Relatively large bodies hidden in these streams may even cause serious local damage when colliding with the Earth. For observers these streams may appear as a firework of bright meteors and fireballs, and even a meteorite dropping. We can, for instance, recall the Tagish Lake meteorite dropping caused by the μ-Orionid fireball stream We can, for instance, recall the Tagish Lake meteorite dropping caused by the μ-Orionid fireball stream (Terentjeva, Barabanov, 2004). Therefore, the observers should always pay attention to these meteorite-producing streams.
Table 1 – The orbital elements for the fireball, eq.2000.0 (Olech et al., 2019) and the τ-Cetids N°50, eq.1950.0 (Terentjeva, 1989, 1990).
|Object name||Date (UT)||αg (°)||δg (°)||v∞
|ω (°)||Ω (°)||i (°)||Π (°)|
|Bukienka fireball||2018 X 6||13.6||–22.9||18.2||1.62||0.510||0.793||67.2||19.45||11.36||86.65|
|τ-Cetids||IX 28 – XI 26||18||–19||20.4||2.442||0.667||0.791||58.4||27.4||11.6||85.8|
As a conclusion, we would like to mention one interesting and extremely rare fireball event described by I. S. Astapovich (1958) in his well-known monograph. Sometimes a big number of fireballs may be observed at once, they may appear as cluster-like formations. I. S. Astapovich recounts several events of this kind: a quasi-simultaneous appearance of 40 fireballs over Prussian Saxony on December 12–13, 1830 (the Geminids?); a large stream having contained several dozens of fireballs that passed over Scandinavia on the 9th of February 1931; and the most grand event that took place on the same day, but 18 years prior to the Scandinavian event from a different apparent radiant. On the 9th of February 1913 three large groups of a hundred of fireballs appeared within 10 minutes and travelled over 8400 km along the line from Canada over the Bermuda Isles to the equator. There are 144 records of this event taken both from boats and ashore. The groups travelled at different altitudes; the lowest passed over Ontario, at 42 km above the ground, and produced prominent noise. Two other groups flew over the Atlantic Ocean with a velocity of 14 km/s.
The observers should always keep in mind that these events, though quite rare, do take place. Thus, they should make enough efforts not to be taken by surprise.
The authors thank Paul Roggemans and Elena Bakanas for all efforts with the preparation of this article.
This work was supported by Program LP RAS 19 – 270.
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