Kappa Cygnids

History

The first observation of this meteor shower was made by N. de Konkoly (Hungary) during the period of 1874 August 11-12. He was observing the Perseid meteor shower and noted that seven of the meteors he plotted intersected at a position of RA=291 deg, DECL=+50 deg, near the star Kappa Cygni. No further observations were reported during the next few years, but then, in 1877, W. F. Denning (England) plotted several meteors from a position of RA=292 deg, DECL=+48 deg while watching the Perseids during the period of August 10-16. Denning again detected activity from this shower during 1885, 1886 and 1887.

Writing in The Observatory in September 1893, Denning wrote how he was "struck with the frequency and brightness of meteors from a contemporary radiant on the N.W. limits of Cygnus near the star κ. Altogether I observed 28 paths directed from the point 292 deg, +53 deg, and must have missed others." The activity was noted during August 5-16. He described the meteors as "rather swift, with short courses, and in a majority of cases the nucleus, before final disruption, burst out very suddenly and left a short streak, marking the spot where it occurred." Denning added that other British observers independently noted the unusual activity from Cygnus---most notably Henry Corder (Bridgwater), J. Evershed (Kenley), and R. A. Batt (Leyton Road)---with several bright fireballs being noted from the region during August 13-17. One very notable finding made by Denning involved the eastward movement of the radiant, with his observations of August 5, 6, and 8 revealing a position of RA=290 deg, DECL=+53 deg, his observations of August 13 and 14 revealing a position of RA=292 deg, DECL=+53 deg, and his August 16 observations indicating a position of RA=296 deg, DECL=+53 deg.

Since most of the August meteor observations made during the 19th Century were typically centered on the date of the Perseid maximum, the actual date of the greatest Kappa Cygnid activity was not clearly understood until early in the 20th Century. Observers then began to notice that the shower was strongest around a week following the Perseid maximum. For example, during 1922, the English observers J. P. M. Prentice and A. Grace Cook independently plotted more meteors from the Kappa Cygnid shower than for any other August shower, excluding the Perseids. The former observer plotted 12 meteors during August 15-20, from an average radiant of RA=291 deg, DECL=+52 deg. Cook plotted 18 meteors during August 15-17, 20 and 26, from a radiant of RA=291 deg, DECL=+50 deg. She called it the "Theta Cygnids." A probable third independent observation came from across the Atlantic as W. H. Christie (Victoria, British Columbia, Canada) plotted 6 meteors from RA=299.5 deg, DECL=+50.8 deg on the night of August 21/22.

Other interesting observations of this shower came in the years that followed. In 1925, the Russian Society of Amateurs plotted 23 meteors during August 16-20, and revealed an average radiant of RA=291.4 deg, DECL=+54.0 deg. Two excellent early observations of this stream were made by American Meteor Society (AMS) members on August 14 of 1936 and 1951. In the first year, Balfour Whitney (Oklahoma, USA) plotted 7 meteors from RA=285 deg, DECL=+57 deg, while Richard Widner (Oregon, USA) plotted 5 in the latter year from RA=289 deg, DECL=+50.5 deg.

Curiously, despite the frequent appearance of this shower in various observational records, it has just as frequently been overlooked. In the previous two paragraphs the observations by Christie, Whitney and Widner mark the only Kappa Cygnid observations among over 6000 radiants on record with the AMS. Similarly, in Cuno Hoffmeister's book Meteorströme, not only is this shower overlooked as an annual producer of meteors, but among the 5406 visual radiants obtained by German observers during 1908-1938, only one observation barely qualifies as a Kappa Cygnid radiant. On August 21, 1930, a radiant was detected at RA=289 deg, DECL=+61 deg and was given a weight of 6 on a scale of 1 to 10.

Although additional visual observations were occasionally reported during the 1940's and 1950's, a newer more substantial view of the Kappa Cygnids was finally achieved in 1954 when F. L. Whipple published the first list of photographic meteor orbits. He determined the orbit of each meteor by measuring the track on photographs obtained at two different stations. Of 144 meteor orbits published in this paper, 5 were identified as Kappa Cygnids. These meteors indicated a duration of August 9-22, while the average radiant was RA=291.5 deg, DECL=+53.0 deg. Whipple commented that the orbits indicated this stream has a "short-period comet orbit with high inclination, period 7-8 years, [aphelion] of 7-8 a.u. The long duration...suggest remnants of a large comet."

The next important event in meteor studies involved radio-echo observations and the Kappa Cygnids were finally recognized by this technique in the early 1960's. Z. Sekanina detected this stream during the 1961-1965 session of the Radio Meteor Project. Activity was detected during August 23-28 from an average radiant of RA=298.9 deg, DECL=+62.4 deg. The stream's occasional disappearance, noted earlier among visual observations, is also evident in Sekanina's 1968-1969 session of the Radio Meteor Project. Despite the radio equipment being operated during August 11-15, 17-18 and 25-30, the Kappa Cygnids were either too weak to be delineated by the computer or totally nonexistent.

Whether the Kappa Cygnids are actually absent in some years cannot be answered since the stream has never been the focus of intensive observations. What is apparent is that the hourly rates of the shower do seem to vary. The first determination of the Kappa Cygnid activity levels came from an observation by Denning on August 22, 1879, when 52 of this shower's meteors were seen during 5 hours of clear sky. With increased visual observations, the variations in activity have been especially noted in recent years. In 1974 the Hungarian Meteor Team obtained a peak ZHR of 23.6±5.1. In 1982 observers of the Nippon Meteor Society estimated a peak ZHR of 14.1, while members of the Dutch Meteor Society obtained a maximum ZHR of only 2-3 in 1984.

Aside from occasional hourly rates, visual details of the Kappa Cygnid meteors have rarely been obtained. During the 1970s and 1980s only two observers obtained this kind of data on this radiant. Robert Lunsford (California, USA) determined the average magnitude as 3.34 in 1977 and 3.00 in 1978, while Paul Roggemans (Belgium) determined the average magnitude as 3.00 in 1986. No estimates are available for the percentage of meteors exhibiting trains.

The Author has sifted through the published lists of photographic meteor orbits and has isolated 9 meteors that are probable members of the Kappa Cygnid stream. They indicate a duration extending from July 26 to September 1. The date of the nodal passage is August 17 (Solar Longitude=143.4 deg), at which time the radiant is at RA=287.6 deg, DECL=+53.8 deg. The indicated daily motion of the radiant is +0.50 deg+/-0.06 deg in RA and +0.15 deg+/-0.12 deg in DECL.

Orbit

The only radar study to detect this stream was Sekanina's 1961-1965 session of the Radio Meteor Project. The orbit was given as

ωΩiqea
203.1152.542.90.9790.6212.583

Nine photographic meteor orbits were gathered by the Author from various sources of photographic meteor orbits. The average orbit was

ωΩiqea
202.7143.438.00.9770.7934.720

Observing

With a duration spanning July 26 to September 1, this shower has been observed almost annually since about the mid-19th century. The maximum is complex, but seems to mainly occur around August 18 (Solar Longitude=145 deg), with an average rate of about 6 meteors per hour. There is evidence to suggest widely varying activity rates and occasional increases in fireball production. The radiant is at RA=289 deg, DECL=+55 deg when the shower reaches maximum. The meteors are of moderate speed and are usually described as bluish-white in color. Their average brightness is about 3. The daily motion seems to be about +0.5 deg in RA and +0.2 deg in DECL.