April Ursids

Observing

The duration of this shower is fairly long, extending from March 18 to May 9. At maximum on April 19, the average radiant is at α=149°, δ=+55°.

History

The April Ursids were observed extensively during the last third of the 19th century and into the 20th century, but their current appearance seems primarily limited to occasional bright meteors and telescopic activity.

The April Ursids were first observed by E. Heis (Münster) during April 16-30, 1849-1861, when he determined the radiant position as RA=150 deg, DECL=+61 deg. However, the most extensive set of observations was made by G. Zezioli (Bergamo, Italy), who plotted meteors from this shower during both 1868 and 1869. According to G. V. Schiaparelli's analysis, Zezioli observed 10 meteors from RA=163 deg, DECL=+47 deg on April 10, 1869, another 10 from RA=168 deg, DECL=+47 deg on April 14, 1868-1869, and 12 meteors from RA=142 deg, DECL=+53 deg on April 25, 1868. All of these radiants possessed D-criterions of 0.04 to 0.10.

Although a few additional radiants were detected during the 1870's, only occasional fireball and stationary meteor observations were made during the next 30 years. Finally, during April 14-18, 1915, William F. Denning plotted four meteors from RA=161 deg, DECL=+58 deg. Interestingly, neither Meteorströme, the American Meteor Society, or any other source has revealed any further visual radiant from this stream.

Individual meteors continue to appear from this stream. Six photographic meteors were detected in three surveys during the period of 1950 to 1969. The indicated duration is April 7 to 23, with an average radiant of RA=173.7 deg, DECL=+59.0 deg. Several fireballs have also been noted, which prompted Charles P. Olivier to include a radiant from this stream in his "Catalogue of Fireball Radiants." Possessing an average position of RA=167 deg, DECL=+63 deg, radiant number 5053 had an estimated endurance of six days centered on April 25.

The most convincing modern-day support for this stream's existence comes from the 1968-1969 session of the Radio Meteor Project. Zdenek Sekanina detected a stream active over the period of March 18-May 9. The radar stream's nodal passage was given as April 18.7 (λ=28.2 deg), at which time the radiant position was RA=149.3°, DECL=+54.9°.