Pi Virginids

Observing

The duration of this meteor shower extends from February 13 to April 8, with maximum occurring sometime between March 3 and 9 (λ=342-348°). The average radiant during maximum is RA=182°, DEC=+3°, while the ZHR seems to peak at 2-5.

History

The discovery of the Pi Virginids should be attributed to Cuno Hoffmeister, who, in his 1948 book Meteorströme, included a meteor shower meeting this stream’s basic description among the nine visual radiants making up his “Virginid Complex.” This was the earliest of the active Virginid showers, with maximum occurring at a λ=344.5°, from RA=178.8°, DEC=+0.6°. Nine visual radiants had been collected during 1908 to 1938, which provided the data for the Pi Virginids.

Visual radiants from this stream are not prominent in the records. The Author has noted that the overall confusion of activity in the entire Virginid region during March and April generally makes visual observations useless—especially in the 19th century, when Denning’s stationary radiant theory was in full swing. At that time, Denning noted weak, but continuous activity during March and April from a position matching that of the Pi Virginid maximum. However, since, the radiant of this stream moves steadily southeastward, one can only conclude that these “stationary” Virginid radiants were the product of several different streams of the Virginid complex. Careful, accurate plots are one answer to studying showers of the Virginid complex. Another accurate method of studying these streams, and, especially the Pi Virginids, is by the use of radar.

Radar studies revealed definite traces of the Pi Virginids during the 1960s. The first study was that of B. L. Kashcheyev and V. N. Lebedinets, both of the Kharkov Polytechnical Institute (USSR). When the radar began operating on March 14, the first members of the Pi Virginids were detected and observations of stream members continued until March 23. The average radiant was given as RA=188°, DEC=+1°. In the following year, C. S. Nilsson (University of Adelaide, South Australia) conducted a radar survey which ultimately revealed three meteors during the period of March 13-16. These meteors came from a radiant of RA=189°, DEC=-4°. On this occasion, the radar equipment only operated during March 11-16, so that later activity would have easily been missed. It is also interesting that Nilsson noted many other meteors in the vicinity of this radiant, but he stated that the equipment was not capable of resolving the individual radiants displaying activity.

Both sessions of the Radio Meteor Project, conducted by Zdenek Sekanina at Havana, Illinois, during the 1960s, detected the Pi Virginids. The first session occurred during 1961-1965. It indicated the shower’s duration was February 23-March 13, with a nodal passage on March 5.8 (λ=344.7°), and an average radiant of RA=182.4°, DEC=+7.4°. The second session was conducted during 1968-1969. On this occasion, the duration was determined as February 13-April 8, while the nodal passage came on March 9.0 (λ=347.9°). The average radiant was RA=184.1°, DEC=+0.5°.

Recent observations of this shower have been made by members of the Western Australia Meteor Section. In 1979, shower members were detected during March 2-5, with a maximum ZHR of 2.28+/-1.02 coming on March 3, from RA=182°, DEC=+7°. In 1980, shower members were detected during March 2-10. A maximum ZHR of 5.38+/-3.11 came on March 3, from RA=183°, DEC=+9°.

Orbit

Orbits have been determined for this stream on four occasions—all during the 1960’s and all during radio-echo surveys. Kashcheyev and Lebedinets’ 1960 survey was based on 9 meteors. Nilsson’s 1961 survey orbit was based on 3 radio meteor orbits. Sekanina’s 1961-1965 survey was based on 9 meteors and his 1969 survey was based on 60 meteors.