The duration of these meteor showers extends
from February 2 to February 25. Maximum occurs around February 8. The Alpha
Centaurids emanate from RA=216 deg, DECL=-60 deg, while the Beta Centaurids have
a radiant of RA=208 deg, DECL=-58 deg. Despite the closeness of the radiants,
they do have differences. The Alpha Centaurids have maximum hourly rates of 3,
while the Beta Centaurids can reach hourly rates as high as 14. The Alpha
Centaurids have an average magnitude of 2.45, while the Beta Centaurids are
probably about 1.6.
This discovery of this shower should be
attributed to Michael Buhagiar (Western Australia), who obtained observations of
both Centaurid radiants during 1969-1980. In his "Southern Hemisphere Meteor
Stream List" of 1980, Buhagiar listed two radiants which reached maximum on
February 7. "Radiant 290" was active during February 6-8, from RA=206 deg,
DECL=-57 deg, while "radiant 299" was active during February 5-9, from RA=214
deg, DECL=-64 deg. Both radiants were referred to as "Beta Centaurids."
Although both radiants have continued to be
observed following the publication of Buhagiar's meteor stream list, observers
have rarely distinguished between the two radiants during the same year.
During 1979, members of the Western Australia
Meteor Section (WAMS) managed to observe the "Alpha Centaurids" during February
2-18. At maximum on February 7, the radiant is at RA=216 deg, DECL=-59 deg.
During 1980, the same group observed members of the "Alpha Centaurids" during
February 2-24. They noted that maximum came on February 8, from RA=209 deg,
DECL=-58 deg. The 1979 radiant obviously represents the true Alpha Centaurids,
while the 1980 radiant is the Beta Centaurids.
Although it is possible that Cuno Hoffmeister
observed this shower (RA=210 deg, DECL=-57 deg) on 1938 February 2, while in
South Africa, the observational history of this stream essentially began in
1969, so that the characteristics of each shower are hard to determine.
Nevertheless, some interesting details should be noted. First of all, the Alpha
Centaurids are apparently a consistent shower, with Buhagiar assigning an hourly
rate of 3, and WAMS observers detecting high rates of 2 (ZHR calculated as
8.564.94) in 1979. The Beta Centaurids are apparently variable in activity,
according to Buhagiar, with his 1969-1980 observations revealing high rates of
10 meteors per hour. WAMS observers obtained maximum rates of 11-14 per hour
(ZHR calculated as 28.484.88) during a one-hour interval on 1980 February 8/9.
Characteristics of the Centaurid meteors have
also been gathered in recent years. During 1979, 20 Alpha Centaurids revealed an
average magnitude of 2.45, while, during 1980, 169 Beta Centaurids revealed an
average magnitude of 1.6 (the latter number is an approximation by the Author
based on a table published in the October 1980 issue of Meteor News).
The Alpha Centaurids may have been detected
by radar at Adelaide Observatory during 1969. G. Gartrell and W. G. Elford
operated the radar system during February 10-17. Two meteors were noted from a
radiant of RA=223 deg, DECL=-61 deg, with the date of nodal passage being
determined as February 15. Assuming these meteors are members of the Alpha
Centaurids, then this stream orbit has an inclination near 105 deg, and a
semimajor axis near 2.5 AU. This identification would also indicate that the
radiant's daily motion is very close to deg in RA. The movement in DECL can not
be determined from the available observations.
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