The duration of this shower persists from March 22 to April 8.
Maximum seems to occur between March 29 and 31 (solar longitude=7
deg-9 deg), from an average radiant of RA=244 deg, DEC=+62 deg.
- 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
deg-diameter radiant at RA=247 deg, DEC=+63 deg. Another
observation came on April 1, 1911, when 12 meteors came
from a 2 deg-diameter radiant at RA=246 deg, DEC=+69 deg.
The three additional radiants were at RA=244 deg, DEC=+61
deg (April 5, 1919), RA=253 deg, DEC=+54 deg (April 7,
1931), and RA=251 deg, DEC=+59 deg (March 23, 1936).
- Two members of the American Meteor Society (AMS) have
also detected activity from this stream. On April 4.3,
1940, Donald 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 RA=257
deg, DEC=+56 deg. On March 31.6, 1951, Philip Burt
(Memphis, Tennessee) plotted 9 meteors from a radiant of
RA=247 deg, DEC=+63 deg. 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 RA=231.0 deg, DEC=+56.2 deg. 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 RA=237.0 deg, DEC=+60.0 deg, while the radiant
diameter was given as 2.0 deg. 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 deg-diameter radiant at
RA=241.0 deg, DEC=+61.5 deg, while, on March 29.88,
Smirnov, Kopycheva and L. M. Afanas'eva plotted 17
meteors (1 stationary) from a 1.5 deg-diameter radiant at
RA=245.5 deg, DEC=+63.5 deg.
- 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 deg across at
RA=237.0 deg, DEC=+61.0 deg. The second radiant was seen
by Tsarev and B. M. Belyakov during March 24-28. Six
meteors came from an area 1.5 deg across centered at
RA=255.0 deg, DEC=+64.5 deg.
- A search through the various records of photographic
meteor orbits by the Author has revealed no possible
members of this stream; however, among Zdenek 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 RA=247.0 deg, DEC=+61.9 deg. The second stream
orbit is based on 8 meteors, with an indicated duration
of March 24 to April 8, and an average radiant of
RA=250.1 deg, DEC=+54 deg. Neither of these streams were
noted by Sekanina.
- Searching through the 39,145 radio meteor orbits obtained
by Zdenek Sekanina, the Author has located 15 meteors
which may be associated with the Eta Draconid stream. The
meteors form two distinct groups, as is demonstrated by
the two orbits below. Orbit "A" is based on 7
meteors, while orbit "B" is based on 8.
- During 1981, Jack D. Drummond (New Mexico State
University) computed the theoretical meteor radiants for
178 long-period comets. Comet Abell was listed as
producing a radiant at RA=254 deg, DEC=+57 deg on March
23 (solar longitude=2.3 deg). The closest approach
between the orbits of the comet and Earth was given as
0.01 AU. The orbit of this comet is also given below.
|
A |
B |
Comet Abell (1954 X) |
Argument of Perihelion () [J2000] |
196.5 deg. |
202.6 deg. |
194.4 deg. |
Ascending Node () [J2000] |
9.6 deg. |
13.8 deg. |
3.0 deg. |
Inclination (i) [J2000] |
38.2 deg. |
48.0 deg. |
53.2 deg. |
Perihelion Distance (q) |
0.984 AU |
0.967 AU |
0.970 AU |
Eccentricity (e) |
0.592 |
0.736 |
1.001 |
Semimajor axis (a) |
2.412 AU |
3.662 AU |
infinity |
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