By Alexandra Terentjeva and Ilya Kurenya
The unexpected abundant meteor shower of June 21, 1937, described by I. S. Astapovich (1940), was caused by the Scorpionids, long known from visual observations. According to photographic data we found that the Scorpionids are part of the ecliptic complex meteoroid Ophiuchi-Scorpionid stream (No. 93, Terentjeva, 1966). The observed phenomenon indicates the presence of significant local concentrations in the stream, which, if the stream encounters Earth under favorable conditions, can cause abundant meteor showers.
I. S. Astapovich (1940), giving the observation data collected by A. A. Shreider, V. I. Belyaev, and K. I. Yermolaeva in the Sarykamysh Depression, wrote about this phenomenon: “… the hourly number of meteors, despite the full Moon (stars weaker than +3 magnitude were not visible), reached 90 after 16h UT; meteors poured “in bunches” from the radiant α = 239°, δ = –23° (1880.0), lying 5° from the Moon. At 21h UT, the phenomenon ended. The meteors were bluish, all of them brighter than +3 magnitude. Here lies the radiant of the famous Scorpionid cosmic shower, active permanently for almost 100 years. The observed phenomenon indicates the presence of significant local concentrations in the cosmic streams, which was not known until now.”
In 1949, while making meteor observations on June 22, I. S. Astapovich (1949) turned his attention to the unusual abundance of meteors from the radiant α = 249°, δ = –19° (1900.0), located on the boundary of the constellations of Scorpius and Ophiuchus. During the previous two weeks, the shower was incessantly active but weak (2–3 meteors per hour). Observations on June 22 gave the hourly number of meteors of 24. Radiant dispersion covered an area of 4°. I. S. Astapovich wrote further (1949): “It was giving the impression that the intensity of the shower was decreasing and that its maximum had been a few hours before the beginning of observations in Ashkhabad, when it was still light.” In his visual observation system, I. S. Astapovich estimated the geocentric velocity of the shower at about 30 km/s. He also believed it possible that the shower should have the period of 12 years according to its previous maximum of 1937.
First of all, it should be noted that the period of 12 years for the Scorpionid shower is no longer to be assumed. The intensity of the shower in 1949 was almost four times lower. Second, it is not known whether its maximum took place a few hours before the beginning of observations in Ashkhabad (when it was still light) or not. In 1949 Earth may have encountered another “concentration” in the stream on the orbit with a different period. But most importantly, by now, in a period of 12 years, the “concentration” of 1937 should have returned to Earth exactly seven times. So why have these maxima of activity not been registered? It is possible, of course, that, as a result of planetary perturbations, the orbit of the stream has ceased to approach the Earth’s orbit, or this “concentration” has dissipated, like the Andromedids did once before the eyes of astronomers of one generation.
What do modern photographic observations of the Scorpionid shower show? According to them, there is a meteoroid stream of the Ophiuchi-Scorpionids (No. 93, Terentjeva, 1966). It is a highly disturbed ecliptic stream with a very wide range of radiants active from June 22 to 30. Obviously, the stream has N and S branches (possibly an ecliptic Q branch, too). The Scorpionid stream is included in this stream as its part. The Ophiuchi-Scorpionid stream includes six photographic orbits. Two orbits with radiants close to those of 1937 and 1949 are listed here. (See Table 1).
Table 1 – The orbital elements for the Scorpionids, eq. 1950.0 (No. 93, Terentjeva, 1966).
|Date (UT)||αg (°) δg (°)||v∞ km/s||a AU||e||q AU||Q AU||ω (°)||Ω (°)||i (°)||π (°)|
|54 VI 25.22||240 –25||18.2||3.50||0.75||0.89||6.1||45||273||1||318|
|54 VI 30.35||249 –16||16.7||2.45||0.64||0.90||4.0||226||98||2||324|
These are the Scorpionids themselves as part of the wide stream of the Ophiuchi-Scorpionids. These are short-period orbits with periods P = 6.5 and 3.8 years. An orbit with an aphelion of 6.1 AU at an inclination of 1° should experience significant perturbations from Jupiter at close encounter with it. This may have been the reason for the alteration of the orbit of the Scorpionids after 1937.
In conclusion, it is interesting to cite an extract from an article by I. S. Astapovich (1954): “According to our interpretation, the stone meteorite of May 19–29?, 1419 in Velikiy Novgorod, described in Russian annals, may belong to the shower of the Scorpionids. The ancient Greek myth of Phaethon was deciphered by us as the flight and fall of a large meteorite from the same constellation at the beginning of the first millennium BC. If that’s true, the Scorpionids have been active for three thousand years.”
In the meteoroid stream of the Ophiuchi-Scorpionids, there are local concentrations which, if the stream encounters Earth under favorable conditions, can cause abundant meteor showers. Who knows, maybe this “legendary” shower will surprise us with its unexpected action – a fall of a meteorite.
This paper was translated into English by I. Kurenya.
The authors thank Paul Roggemans for his efforts enabling the preparation and publication of this paper.
Astapovich I. S. (1940). “The unexpected meteor shower on June 21, 1937”. Nature, No. 7, 105. (In Russian).
Astapovich I. S. (1949). “The maximum of the Scorpionids on June 22, 1949”. Astron. Tsirk. AN SSSR, No. 89, 3–4. (In Russian).
Astapovich I. S. (1954). “On some patterns in small body systems”. Trudy Stalinabad. Astron. Obs. AN Tajik SSR, 20, 78–105. (In Russian).
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.