This minor meteor shower is visible during the period of
December 11 to January 21, and reaches its maximum activity
during December 31 (Solar Longitude=279 deg), from an average
radiant of RA=77 deg, DECL=+35 deg. Though the greatest activity
seems to be detectable only by means of radar or telescopes,
numerous visual radiants and photographic meteors indicate some
activity is visible with the naked eye. A northern branch is also
present during December 11 to January 15. Its maximum comes on
January 2 (Solar Longitude=281 deg), from RA=65 deg, DECL=+57
deg. The meteors of both showers are generally slow moving.
- First detection of this shower was made by William F.
Denning during December 24-31, 1885-1886, when a radiant
at RA=77 deg, DECL=+32 deg was noted producing slow
meteors. On December 27, 1863, Alexander S. Herschel was
one of several people who observed a fireball from RA=75
deg, DECL=+30 deg. Calculations revealed Herschel's
fireball possessed a velocity of 32 km/s, which is
identical to results obtained by Denning after analyzing
observations of a bright meteor observed from RA=77 deg,
DECL=+30 deg on December 28, 1886.
- The true magnitude of this stream seems hard to
determine, but some sense has been made out of the data
after studying Zdenek Sekanina's radar data secured
during the two phases of the Radio Meteor Project. The
results seem to indicate a definite stream producing a
shower during the period of December 14 to January 16;
however, as can be viewed in the "Orbit"
section below, the 1961-1965 survey possessed a smaller
orbital inclination of nearly 7 deg, while the 1968-1969
survey indicated an inclination of about 11 deg. A
possible explanation might involve the fact that the
1968-1969 session possessed a gap in the observational
records that extended from December 21, 1968 to January
12, 1969. As a result, the period of maximum activity was
missed and while the 1961-1965 survey revealed the stream
to have crossed the ecliptic on December 30.9 (almost
exactly at the time of the shower's expected maximum),
the 1968-1969 survey showed the stream to have crossed
the ecliptic on January 13.9.2 Thus, it seems this gap
not only reduced the number of meteors being observed,
but also influenced the shower's apparent distribution of
meteor activity.
- A notable feature among records of meteor activity for
the first half of January is that radiants are frequently
present in Auriga, but, when the positions are plotted,
it seems activity is likely to occur in a region whose
dimensions are about 10 degx30 deg. It should be kept in
mind that this is based on radiants observed during the
last 100 years. For any particular year the radiant seems
to be less than 10 deg across. Examples of some of these
observed radiants and fireballs are as follows:
Zeta Aurigid Radiants and Fireballs
Year |
Date |
RA (deg) |
DECL (deg) |
Source |
1863 |
Dec. 27 |
75 |
+30 |
D1899 |
1885-86 |
Dec. 24-31 |
77 |
+32 |
D1899 |
1886 |
Dec. 28 |
77 |
+30 |
D1899 |
1888 |
Dec. 24-29 |
88 |
+61 |
D1899 |
1891 |
Jan. 6-9 |
85 |
+61 |
D1899 |
1913 |
Jan. 2.82 |
75 |
+30 |
D1916 |
1921 |
Jan. 14.5 |
86 |
+42 |
H1948 |
1932 |
Jan. 1 |
82 |
+36 |
O1934 |
- Interestingly, although most of these visual radiants
originated from what might be considered as the
"southern branch" of this stream, consulted
lists of photographic meteors reveal a fairly
well-defined "northern branch" consisting of 11
meteors detected during the Harvard Meteor Project
conducted during 1952 to 1954. Eight meteors gathered
from American and Russian sources form a fairly diffuse
"southern branch."
- The photographic northern branch seems to persist from
December 11 to January 15, but may be active as early as
December 1 and as late as January 21. Maximum activity
seems to occur between December 28 and January 2, from an
average radiant of RA=65 deg, DECL=+57 deg.
- From the accumulated data, the Author sees the Zeta
Aurigids as a split stream, with most photographic and
visual data indicating the northern branch possesses a
greater population of large particles. Most of the
information gathered on the southern branch reveals it
contains primarily small particles, which are easily
detectable using radar equipment; however, this branch
has produced several fireballs in the past, which is a
feature not present in the northern branch.
- The radar orbits which were determined from the two
phases of the Radio Meteor Project conducted by Sekanina
at Havana, Illinois, during the 1960's are as follows:
|
1961-5 |
1968-9 |
Argument of Perihelion () [J2000] |
235.8 deg. |
221.0 deg. |
Ascending Node () [J2000] |
279.7 deg. |
293.9 deg. |
Inclination (i) [J2000] |
6.7 deg. |
11.1 deg. |
Perihelion Distance (q) |
0.816 AU |
0.901 AU |
Eccentricity (e) |
0.602 |
0.513 |
Semimajor axis (a) |
2.053 AU |
1.851 AU |
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