April Piscids

Observing

This daylight shower is detectable during the period April 8 to 29. It reaches maximum around April 20 (λ=29°) from an average radiant of α=7°, δ=+5°. Due to inconsistencies in the quantity of meteors detected in four separate radar surveys, this stream may be periodic in nature.

History

This meteor stream was discovered by B. L. Kashcheyev and V. N. Lebedinets (Kharkov Polytechnical Institute, USSR) during a radar survey in 1960. Thirty-four radio meteors were detected during April 15-25, with the average radiant being α=7°, δ=+3°. The date of the stream's nodal passage was given as April 20/21.

This stream was again detected during 1961, while C. S. Nilsson (University of Adelaide, South Australia) was conducting a radio survey of southern hemisphere meteor streams. Only three meteors were noted during the interval of April 13 to 29. The indicated date of the nodal passage was April 18/19, at which time the radiant was located at α=6.5 deg, δ=+4.3 deg. Nilsson said his stream actually did not qualify as a group, due to the excessive "scatter in the values obtained for the right ascension;" however, he noted a close agreement between the orbits of this stream and a stream detected in August, which the Author has identified with the Northern Iota Aquarids.

It is surprising that this stream was not recognized by Zdenek Sekanina in either of the two sessions of the Radio Meteor Project. In an attempt to discover why, the Author examined the 39,145 radio meteors orbits determined by Sekanina. The radio equipment at Havana, Illinois, operated during April of 1962-1965 and in 1969. Thirteen probable members of the April Piscids are present in the sample. These meteors indicate a duration extending from April 8 to April 26. The date of the nodal passage is determined as April 19/20 (λ=29.7°), at which time the radiant is at α=7.4°, δ=+7.2°. What is most interesting is the yearly distribution: 5 meteors in 1962, 1 in 1963, 4 in 1964, 2 in 1965, and only 1 in 1969.

When Sekanina's data is compared with that obtained in the Russian and Australian surveys discussed earlier, it appears that the Russian data was based on an uncharacteristic return of this stream, with 34 meteors being detected. In fact, the 1968-1969 session of the Radio Meteor Project involved the most sensitive equipment ever used in radar meteor surveys and April was well covered. The fact that only 1 meteor was detected in 1969, indicates this daylight stream may be periodic.