April Virginids

History

This meteor shower probably represents one of the weaker branches of the Alpha Virginid stream. Its orbital elements are very similar (though separated by 180° in the argument of perihelion and ascending node), but its inclination is about 13 deg higher.

The primary support for this stream's existence is the fact that it was detected by Zdenek Sekanina in both sessions of the Radio Meteor Project. The 1961-1965 survey revealed meteors during April 5-10, with the nodal passage coming on April 7.3, and the average radiant being RA=213.4°, DECL=-1.1°. The 1968-1969 survey only detected meteors on April 7 and 8, since the radar had been shut down during March 29 to April 6. The date of the nodal passage was given as April 7.8, while the average radiant was determined as RA=213.1°, DECL=+3.6°.

The Author has collected eight photographic meteors from MP1961. The indicated duration is April 1-16. The nodal passage falls on April 11, at which time the radiant is at RA=215.6°, DECL=-0.9°.

A comparison of the photographic and radar orbits indicates no significant difference in the shapes and sizes of the two types of orbits, although the nodal passage of the photographic meteors does occur about 3 days later than that given for the radar meteors. Noting this similarity, the Author combined 15 of the radio meteor orbits and the 8 photographic orbits in an attempt to determine the daily motion of the radiant. The result was +0.77° in RA and -0.17° in DECL.

Only three probable visual observations of this stream were made prior to Sekanina's discovery. The first observation was made by Cuno Hoffmeister on April 6, 1933 (Solar Longitude=15.5 deg), when the radiant was given as RA=212°, DECL=+5°. The next observation was also made by Hoffmeister, this time on April 7, 1934 (λ=17.5°), when the radiant was given as RA=210 deg, DECL=-4 deg. The third observation was made by Franklin W. Smith (Glenolden, Pennsylvania) on April 8, 1934---less than 24 hours after Hoffmeister's second observation. The radiant was given as RA=211°, DECL=+2°.

In an article published in 1973, E. I. Kazimirchak-Polonskaya and A. K. Terent'eva showed the evolution of several theoretical particles within the Alpha Virginid stream. According to their tables showing details of this orbital evolution, the Alpha Virginids can attain a high inclination of 14 deg (during the 200 years examined), but usually did not spend too many years in that configuration due to fairly frequent approaches to within 0.32 AU of Jupiter. This Soviet study demonstrates that any meteors left in such an orbit would not be plentiful. Such is the case with the April Virginids, as only seven visual radiants appear in the major visual lists of radiants published from 1899 to the present.