Eta Draconids

History

Observations of the Eta Draconids seem confined to the 20th century. In Cuno Hoffmeister's book, Meteorströme, five German-observed radiants are listed which apparently belong to this stream. The first observation was made on April 2, 1910, when 20 meteors were detected from a 2°-diameter radiant at α=247°, δ=+63°. Another observation came on April 1, 1911, when 12 meteors came from a 2°-diameter radiant at α=246°, δ=+69°. The three additional radiants were at α=244°, δ=+61° (April 5, 1919), α=253°, δ=+54° (April 7, 1931), and α=251°, δ=+59° (March 23, 1936).

Two members of the American Meteor Society (AMS) have also detected activity from this stream. On April 4.3, 1940, D. Faulkner (Stetson University, Florida) coordinated two teams of students to observe the Eta Aquarids. The groups were located at Daytona Beach and Altoona, and all observed meteors were plotted. Faulkner's evaluation of the data revealed that both stations had detected meteors from a radiant at α=257°, δ=+56°. On March 31.6, 1951, P. Burt (Memphis, Tennessee) plotted 9 meteors from a radiant of α=247°, δ=+63°. The records of the AMS are probably the most extensive collection of visual radiants in the world for the 20th century, yet it seems a puzzle that only two observations of the Eta Draconids appear in their records. On the other hand, the Author has noted that when meteor observations are made during March (and they are rare), they are usually of the southern portion of the sky. The same is true for the early half of April.

The most impressive collection of data on this stream to date was described by T. L. Korovkina, V. V. Martynenko and V. V. Frolov in a paper published in 1971. The Eta Draconids were one of 23 meteor showers detected during observations in March 1969. Participating in the survey were members of the Yaroslavl Society of Amateur Astronomers and the Yaroslavl division of the Astronomical and Geodetic Society of the USSR. Observers were split into two groups, with one observing at Krasnye Tkachi during March 24-30, and the other observing at Rybinsk during March 6-16 and 25-29. The limiting magnitude of the sky during these observations was between 5 and 5.5. The observers at the former village had set their objective as searching for radiants of minor meteor showers and they were the successful observers of the Eta Draconids.

E. A. Malakhaev observed the first possible radiant on March 26.99, when 9 plotted meteors indicated a 1.0 deg-diameter radiant at α=231.0°, δ=+56.2°. On a scale of 1 to 5, the accuracy of this radiant was given as 3. A similar value was also assigned to a radiant detected by Malakhaev, N. V. Smirnov and T. A. Kopycheva during March 27.98. Based on 8 meteors, the position was given as α=237.0°, δ=+60.0°, while the radiant diameter was given as 2.0°. Two excellent radiants were determined during the following two nights: on March 28.91, Smirnov, Kopycheva and V. K. Karpov plotted 16 meteors (1 stationary) from a 2.0°-diameter radiant at α=241.0°, δ=+61.5°, while, on March 29.88, Smirnov, Kopycheva and L. M. Afanas'eva plotted 17 meteors (1 stationary) from a 1.5°-diameter radiant at α=245.5°, δ=+63.5°.

The 1969 survey was repeated on a smaller scale during 1973. Smirnov and T. L. Korovkina published their evaluations of the visual data in 1975, and indicated that observations were primarily conducted during March 24-30 by members of the Yaroslavl Amateur Astronomers Society in Krasnye Tkachi. Overall, the 1973 observations revealed less activity from the Eta Draconids than was detected in 1969, but two radiants were nevertheless noted which might be related in some way. The first radiant was seen by N. A. Tsarev and Smirnov during March 25-29. Four meteors came from an area 1.0° across at α=237.0°, δ=+61.0°. The second radiant was seen by Tsarev and B. M. Belyakov during March 24-28. Six meteors came from an area 1.5° across centered at α=255.0°, δ=+64.5°.

A search through the various records of photographic meteor orbits by the Author has revealed no possible members of this stream; however, among Z. Sekanina's 39,145 radio meteor orbits, 15 probable members were found which seem to indicate two distinct streams. The first stream is based on 7 meteors. The indicated duration is March 22 to April 9, while the average radiant is α=247.0°, δ=+61.9°. The second stream orbit is based on 8 meteors, with an indicated duration of March 24 to April 8, and an average radiant of α=250.1°, δ=+54°. Neither of these streams were noted by Sekanina.