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(meteorobs) NAMN Special Project: 1996 Leonids
Hi Everyone,
In November, the NAMN will once again team up with the International Meteor
Organization on a special project of observing the 1996 Leonid meteor shower.
During normal years, the Leonids produce about 15 meteors or so per hour at
maximum. However, they are an unusual shower in that they are what is known as a
periodic shower, and one that has in the past, produced meteors up to storm
levels. Meteor storms are very rare events, producing hundreds and sometimes
thousands of meteors per hour. An observer would be considered lucky to see
one meteor storm in a lifetime, so the event is not one to be missed!
A search of historical records show that the Leonids have been observed probably
since the year 902 (Roggemans, 1989). But they weren't recognized as a meteor
shower until after the storm of November 13, 1833. Shortly after that, it
was found that the Leonids exhibited what seemed to be a 33 year period, and
a prediction was made that another storm would occur in 1866. And what a
storm it was - peak Leonid rates were reported as high as 5,000 per hour.
Shortly afterwards astronomers noted that the orbit of the Leonids and Comet
Tempel-Tuttle (now known to be the parent source) were very similar.
With the 33 year orbits of both comet and meteor shower established, astronomers
began predicting the next storm to occur in 1899. Unfortunately, meteor
showers do not always cooperate, and they failed to produce the predicted
storm, prompting Charles P. Olivier (founder of the American Meteor Society)
to call this "the worst blow suffered by astronomy in the eyes of the public."
Thirty-three years later, in 1932, the Leonids did show some enhanced
activity, but not to storm levels like in 1866. Then in 1966 the most famous
of all Leonid storms occurred with the highest rates being reported from
Arizona (USA). On the night of November 17, a group of observers reported
meteors streaking across the sky at a maximum rate of 2,400 per minute!
Due to the 33 year period of the Leonids, another storm may occur toward the
end of this decade. Although not a certainty, most meteor researchers
predict that if it does happen, it would most likely occur in 1998, 1999, or
maybe 2000. It is expected that if this happens, the Leonids should show
some enhanced activity a few years before these predicted dates. This seems
to be happening as according to the IMO, the first signs of an increase in
Leonid activity occurred in 1994 when their estimates put the Leonid ZHR at
about 60 per hour, four times as high as their normal rate of 15 to 20 per hour!
In 1996 conditions are very good for monitoring activity from the shower as the
crescent moon will have set for most places before the Leonid radiant rises
(around local midnight). There are several predictions on when the 1996 peak
will occur. These center on November 17th, and range from 0700 hours UT to
1700 hours UT. With these favorable conditions, I urge all NAMN members,
whether a beginning observer or an experienced one, to plan several nights
of observing around the 17th if at all possible.
Due to this being a special project, normal NAMN reporting procedures will
be modified somewhat. It is extremely important that observers email me a
basic summary of their observations, including magnitude distributions,
immediately after the session is over (less than one hour if at all
possible). Then, when time permits, the full NAMN report can be filled out
and emailed in as normally done.
Sample observing summary and magnitude distribution headers are below which
can be "cut and pasted" and used as a template:
Observing Period:
UT Date UT Time Teff F LM LEO XXX SPO
------------------------------------------------------
Magnitude Distribution:
LEO: (-3)0; (-2)0; (-1)0; (0)0; (+1)0; (+2)0; (+3)0; (+4)0; (+5)0; (+6)0
XXX: (-3)0; (-2)0; (-1)0; (0)0; (+1)0; (+2)0; (+3)0; (+4)0; (+5)0; (+6)0
SPO: (-3)0; (-2)0; (-1)0; (0)0; (+1)0; (+2)0; (+3)0; (+4)0; (+5)0; (+6)0
-------------------------------------------------------------------------
The specifics on the Leonids, from the NAMN Guide is:
Leonids (LEO) Active: Nov 14-Nov 21 Max: Nov 17
Radiant: 153 +22 Diameter: 5 Drift: +0.7 -0.4
Velocity: 71 km/s Population Index: 2.5 ZHR: variable
NOTES: The Leonids are a shower of short duration, lasting only one week
centered on November 18. The Leonids are particles from Comet Temple-Tuttle,
which will reach perihelion in 1998. A great concentration of particles
exists near the parent comet. In years when the comet is far from the inner
solar system the activity remains below 10 meteors per hour. However, for
approximately 10 years centered on the perihelion passage of Temple-Tuttle,
the Leonids can produce marvelous displays of celestial fireworks. We are
now within this period of enhanced activity and one should not miss the
opportunity to watch the Leonids. During periods of high activity, the
Leonids are easy to photograph. Many shower members are bright and leave
long lasting trains. The Leonid stream collides with the earth from a
head-on position that produces the highest velocity of all major showers: 71
km/s, often producing blue, green or white meteors that frequently leave a
train. Fortunately the Leonid radiant is located close enough to the
Celestial Equator that these displays may be enjoyed by both hemispheres.
If anyone has any questions on the Leonids, how to observe them or how to
report your observations, please email me at the address below. I look
forward to receiving your observations and wish all of you good luck, and
clear skies!
Mark Davis
NAMN Coordinator
MeteorObs@charlestondot net