By Alexandra Terentjeva and Galina Bolgova
Abstract: When having studied meteor complexes in the Solar system I. S. Astapovich (1941) found a phenomenon appearing common for various classes of minor bodies ranging from telescopic meteors to giant meteorites. This phenomenon is the tendency of minor bodies to grouping that becomes more prominent among larger objects. The authors describe the idea bу I. S. Astapovich and show how it is proved by nowadays studies covering the whole range of objects from faint meteors to asteroids. The study by A. K. Terentjeva (1966) also shows that even sporadic material does not show totally chaotic behavior. The degree of this chaos decreases with increasing masses of the objects. We dedicate this article to the well-known meteor investigator, founder of meteor astronomy in the USSR, Prof. I. S. Astapovich who passed away 45 years ago.
When studying meteor complexes in the Solar system I. S. Astapovich (1941) found a common property of various classes of minor bodies ranging from the smallest one (telescopic meteors) to large meteoroid bodies – giant meteorites. Let us refresh in memory his idea that remains actual so far and keeps developing. According to Astapovich, telescopic observations of meteors showed that approximately 1% of these bodies comprise binary systems. The same results may be derived from the photographic observations as, for instance, one may see in two catalogues of the Harvard observatory. Sometimes one companion follows another in several seconds.
Ellen Dorrit Hoffleit mentioned that the intervals between the falling meteors belonging to a shower differs from those of sporadic meteors, which may indicate that in showers meteors tend to group, at least in pairs. Now we have lists of binary and multiple objects. One may demonstrate observations of various scientists made in different epochs that indicate the continuous transition from single and binary meteors to small streams containing several dozens of objects and simultaneously penetrating the atmosphere. These observations are available for all classes of meteor bodies. For example, on November 28, 1883 Brooks observed a stream with the 9-inch telescope. For ordinary meteors the same phenomenon was, for instance, observed during a short meteor storm that lasted for only 10 minutes on November 24, 1925 in the State of Virginia, USA. The phenomenon is especially spectacular when we observe fireballs. This may be illustrated by the event that took place on the 9th of February, 1913, when the “procession” comprised of several dozens of fireballs spanned the distance of 8000 km from Ontario to the Islands of Bermuda. It is noteworthy that exactly 18 years later, on the 9th of February, 1931, the stream of 30 – 40 fireballs was observed over North-West Europe. On May 27, 1935 a similar stream passed over the Scandinavian peninsula having allowed the observers to obtain approximately 500 registrations. When we consider larger bodies, the same tendency takes place.
Historical data store information on meteorite storms containing tens of thousands of components (for instance, Pułtusk, Poland, January 30, 1868 ~ 100000 components; Holbrook, Arizona, USA, July 19, 1912 ~ 14000 components). Though meteorites usually fragment in the atmosphere, one can show that they can move in a stream prior to their encounter with Earth. For example, along with the event over Pułtusk meteorites of the same chemical composition precipitated in Lerici, Italy and Nosy Be, the island of Madagascar.
As Astapovich mentioned the tendency of grouping may be common for even larger bodies. For example, the meteorite craters recently found all over the world (Saaremaa island, Baltic Sea; Rub’ al Khali desert, Arabian peninsula; Henbury, Australia; Tunguska, Russia; etc.) are formed after the impacts of streams of giant meteorites (thousands of tons each). Due to their enormous masses they would have to lose the cosmic velocity below the Earth surface, which resulted in impacts at extremely high velocities.
According to Astapovich, the observed grouping – more often encountered among more massive bodies – may indicate a relatively young age of these streams. The streams alike should permanently occur in the Solar system. Historical records (for instance in Chinese archives) witness a relatively high frequency of these events in the past, which, in turn, prompts us to suppose that they happen today, too. Astapovich proposed that these streams may occur after collisions of meteoroid bodies (regardless of their origin, interstellar or solar). He also provides a number of suggestions supporting the idea of permanent collisions. Hereafter we will mention only one of these suggestions.
Astapovich (1939) found that the intersection of trajectories of 10 meteorites, more than 20 meteoroid streams (four of them are major showers), 27 large (often detonating) fireballs, and several comets, occurs at the point with coordinates λ = 216°, β = +2° at a distance of approximately 1 AU from the Sun. In our previous works (Terentjeva, 1991; Galibina and Terentjeva, 1987), we paid special attention to this circumstance, and, in particular, considered a possibility for the existence of a comet-meteor-meteorite system.
2 Research results
Now let us consider the present-day evidences of the phenomenon discovered by Astapovich for the system of minor bodies. It is known that the fraction of “organized” matter among the fainter meteors (up to the magnitude of +7) is only 28% (Kashcheyev et al., 1967). For ordinary photographic meteors this fraction reaches 56% according to (Terentjeva, 1966) or 43% according to (Lindblad, 1971). Among the larger bodies such as fireballs the “organized” matter fraction reaches 68% (Terentjeva, 1990).
When proceeding with asteroids, we see that 130 of 181 (i.e. 72%) bodies approaching the Earth are related to meteoroid streams (Babadzhanov and Kokhirova, 2009). Therefore, these 72% of bodies comprise the “organized” fraction of the asteroids (of cometary origin, according to P. B. Babadzhanov and G. I Kokhirova).
Thus, a pattern in the system of minor bodies is confirmed in the present time: the larger the bodies the more pronounced their tendency to grouping.
3 On the sporadic meteors
Within the period of 1963–1967 A. K. Terentjeva analyzed more than 3700 orbits of individual meteoroid bodies using photographic observations published before 1967 (recording started from 1936) and approximately 2000 visual radiants recorded in the 19th and 20th centuries. This study resulted in the discovery of 359 minor meteoroid streams. A complete bibliography of these streams is given in particular in (Terentjeva and Bolgova, 2020).
It is noteworthy that the rest of the bodies from the above sample, not belonging to any streams, did not show totally chaotic behavior too (Terentjeva, 1966). On the contrary, among these bodies one could find several coinciding characteristics (not all), pick out groups with similar motion (though, this similarity is not accurate enough to convincingly relate these groups to each other), which indicates that the discussed meteoroids may be somehow related. We may then suppose that these are not absolutely sporadic meteoroid bodies, but members of several streams. Their characteristics for some reason differ significantly from the stream’s average, which formally prevents us from associating them to a particular stream. The latter statement is exemplified in the paper mentioned above. The author picked out a numerous group of photographic radiants located around the anti-apex point. This group of radiants is spread over the area with the diameter of 56° (!) in the direction perpendicular to the ecliptic. All the six meteors of this group were observed within 11 days, plus 3 meteors on nearby dates. Common criteria do not allow us to unite this group into a stream, though their relation to each other seems possible if we suppose that this group was considerably disturbed by major planets, included the Earth.
One more example shown in the mentioned paper demonstrates three pairs of “photographic” orbits of sporadic meteoroids. The first pair of almost parabolic orbits surprised the author by the strong similarity of the five orbital elements and the body’s heliocentric velocity, though the inclinations of the orbits differ by 64° (!) radiant positions are 29° (!) apart, and their pre-atmospheric velocities differ by 11 km/s.
L. G. Jacchia and F. L. Whipple (1961) 20 years later than I. S. Astapovich also noted the tendency of meteoroid bodies grouping and picked out 88 associations. The examination of these associations resulted in the conclusion that most of them are structures, whose nature lie between sporadic material and meteor streams. The possible formation of these associations may indicate the similarity of some groups of sporadic complexes.
When we search an asteroid related to a stream, we always start with a sample of 50 – 60 objects. The authors noted that in this samples the behavior of the members is not absolutely chaotic. Oppositely, one always may find a tendency to grouping at least in clusters of two-three objects. We can exemplify the latter by 8 asteroid streams revealed from the sample of 52 Eccentrid asteroids (Terentjeva and Barabanov 2016). We then can suppose that in the sporadic material the discussed phenomenon is more prominent among the largest bodies, asteroids. It is in a sense natural since the population of asteroids is more compact than meteoroid streams.
This year marks 45 years since the death of Igor Stanislavovich Astapovich (11 January 1908 – 02 January 1976), the founder of meteor astronomy in the USSR. He was a person remarkable in his versatility, encyclopedism, and broad erudition. In our country he was known as a “patriarch” of meteor astronomy. His monograph “Meteor Phenomena in the Earth’s Atmosphere” (Astapovich, 1958) was unofficially mentioned as “Meteor Almagest”. The monograph “Interesting stories on meteorites” (Astapovich, 2015) recently became a best-seller (in Russian) thanks to the Academy of education in San Francisco, which actively promotes its dissemination. Hundreds of people from all over the world downloaded it from the Internet. The ideas promoted by I. S. Astapovich remain relevant today and keep inspiring the meteor community to solve new pressing problems. For more information about I. S. Astapovich see, e.g., Terentjeva (2001), Husárik et al. (2009).
Modern studies prove the idea proposed I. S. Astapovich in 1941 that minor bodies tend to grouping, and this tendency becomes stronger with the growing mass of objects.
As the investigations by A. K. Terentjeva (1966) show, the material we call sporadic actually does not display totally chaotic behavior. And the degree of chaos decreases with increasing masses of considered minor bodies.
The authors thank Paul Roggemans for all efforts with the preparation of this paper.
Astapovich I. S. (1939). “Some results of the study of 66 orbits of meteorites”. Astron. Zhurnal AN SSSR, 16, Issue 6, 14–45. (In Russian).
Astapovich I. S. (1941). “Some aspects of origin of meteor matter. Meteor matter in the Solar system”. Astron. Zhurnal AN SSSR, 18, Issue 1, 58–72. (In Russian).
Astapovich I. S. (1958). “Meteor phenomena in the Earth’s atmosphere”. Fizmatgiz. (In Russian).
Astapovich I. S. (2015). “Interesting stories on meteorites”. Astroprint. Odessa. (In Russian).
Babadzhanov P. B. and Kokhirova G. I. (2009). “Meteor showers of asteroids crossing the Earth’s orbit”. Donish. Dushanbe. (In Russian).
Galibina I. V., Terentjeva A. K. (1987). “The Innisfree meteorite: dynamical history of the orbit; possible family of meteor bodies”. Astron. Vestnik AN SSSR, 21, No. 3, 251–261.
Husárik M., Pittich E. M., Solovaya N. A. and Svoreń J. (2009). “Asteroid 2408 upon the 100th birthday of Igor Stanislavovich Astapovich”. Contrib. Astron. Obs. Skalnaté Pleso, 39, 78–84.
Jacchia L. G., Whipple F. L. (1961). “Precision orbits 0f 413 photographic meteors”. Smithson. Contrib. Astrophys., 4, No. 4, 97–129.
Kashcheyev B. L., Lebedinets V. N. and Lagutin M. F. (1967). “Meteor phenomena in the Earth’s atmosphere”. Moscow. (In Russian).
Lindblad B. A. (1971). “Two computerized stream searches among meteor orbits: 1. Among 865 precise photographic orbits; 2. Among 2401 photographic orbits”. Smithson. Contrib. Astrophys., No. 12, 1–24.
Terentjeva A. K. (1966). “Minor meteor streams”. Results of researches of international geophysical projects: Meteor Investigations. No 1, Publishing House “Nauka”, Moscow, pages 62–132. (In Russian). See also eMetN, (2017), 2, 95.
Terentjeva A. K. (1990). “Fireball streams”. In Lagerkvist C. I., Rickman H., Lindblad B. A. and Lindgren M., editors. Asteroids, Comets, Meteors III. Uppsala University, Sweden, pages 579–584.
Terentjeva A. K. (1991). “Several puzzles of meteor astronomy”. Proceedings of the International Meteor Conference, Potsdam, Germany. Published by the IMO, pages 60–66.
Terentjeva A. K. (2001). “Igor Stanislavovich Astapovich (on the occasion of his 90th birthday)”. Astronomical and Astrophysical Transactions. OPA (Overseas Publishers Association), 20, pages 701–716.
Terentjeva A. K. and Barabanov S. I. (2016). “Asteroids in the Eccentrid meteor system”. Solar System Research, 50, No 5, 337–343.
Terentjeva A. and Bolgova G. (2020). “Meteorite-producing stream of the tau-Cetids and a meteorite dropping fireball over Poland”. eMetN, 5, 1–3.