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(meteorobs) NAMN Notes: November 1999
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NAMN Notes: November 1999
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Introduction:
NAMN Notes is a monthly newsletter produced by the North American Meteor
Network, and is available both via email, and on the NAMN website at:
http://web.infoavedot net/~meteorobs
Contents:
1. Here Come the Leonids!...
2. Other November Showers...
3. New Star Charts for Beginners...
4. Meteor Results from September...
5. Radio Observations of Meteors...
6. Upcoming Meetings...
7. For more info...
1. Here Come the Leonids!...
The Leonid shower, predicted to be the highlight of the 1999 meteor
observing year, is just about upon us!
The Leonids (LEO) reach a maximum on November 18th, estimated at 02h08m UT,
according to the International Meteor Organization's (IMO) Leonids 1999
report on their website. These meteors have a radiant at 153 degrees, ie. RA
10h12m, Dec +22, in the upper part of the "sickle" of Leo. In other words,
if you trace their path backwards in the sky, the meteors will all seem to
come from the sickle, the backwards "question mark" of Leo. And this year,
the Leonid shower does indeed hold many questions! These meteors are fast,
with a velocity of about 71 km per second.
The Leonid meteors are debris from Comet 55P/Tempel-Tuttle which has a
period of about 33.2 years. This female Canadian co-author caught a look at
Tempel-Tuttle a year ago March, on a cold winter night, just after it got
dark. I located it by carefully star-hopping in the field of view of my
refracting telescope. In my low power eyepiece, it was just a tiny fuzzy
spot, but rather neat. It was fascinating just to see it in my own
telescope - the comet that produces the Leonid meteor shower!
According to various reports, there is a chance that the Leonids could
"storm" this year. However, according to the IMO, "predictions of the peak
rate are most difficult... judging from the models and the phenomenology of
past returns, the maximum ZHR may be 1000... a background level of about
ZHR 100 lasting several hours is quite certain though." The ZHR, Zenithal
Hourly Rate, refers to the number of meteors you would see with the unaided
eye under a dark sky, if the radiant was directly overhead. If the Leonids
do storm, the predictions seem to favor the longitudes of western Asia,
Europe and Africa. However, meteor showers can be very unpredictable, and
nobody will know for sure what the Leonids will actually do until they do
it!
Many observers are planning to travel to view the Leonids this year.
However, it is very important to have observers around the globe - to gather
observations at widely separated locations. I thought of an interesting
analogy the other night. I don't know how many of you are familiar with a
grazing occultation - that's where a star seems to skim the edge of the moon
and blink on and off in between the mountain tops on the lunar surface. By
having people observe these and time the disappearance and reappearance of
the star as it blinks on and off between the mountains, the professional
astronomers can get a good profile of the moon and refine the lunar orbit to
greater precision. Similarly, by having many meteor observers around the
world record data on the Leonids, the professional meteor astronomers can
get a better profile of the streams and filaments of Comet Tempel-Tuttle
debris, as the earth passes through them.
As a result, all observations are very useful - whether you see high meteor
rates or low meteor rates. Both are equally important to study these streams
and filaments in space! The professionals need as many observations as they
can get, from as many locations as they can get, on as many nights as they
can get! Don't just go out for the best night. Look what happened last
year - that incredible fireball display occurred well before the predicted
"best" time to observe. Try to get out on nights before, and on nights
after, not just the predicted best night! (Note that in order for you to see
Leonids, the radiant must be above your horizon, or at least just about to
rise. This will mean starting your observing quite late in the evening,
depending on your location.)
If you are new to meteor observing, check out our website, print yourself
off some of our new star maps, print off some NAMN meteor recording sheets,
and check out our NAMN Observing Guide as to how to record meteors.
Basically, for each meteor, we try to record the time, its brightness and
what shower it belongs to. That's basically it in a nutshell, although many
discussions make it sound more complicated. Also during the night, we take
note of sky conditions such as cloud and limiting magnitude, which is the
faintest star we can see to give the experts reducing our data an idea of
how good our skies and our eyes are. The NAMN website is at:
http://web.infoavedot net/~meteorobs
There are a lot of good web resources with specific info on the Leonids.
Check out several of the following:
Sky and Telescope's Meteor Page:
http://www.skypub.com/sights/meteors/meteors.shtml
articles include How to Plan a Meteor Watch, and Awaiting the Storm (1999
Preview)
IMO, International Meteor Organization:
http://www.imodot net
includes info on visual, photographic and video observations, and a neat
computer software simulation of a meteor storm - MetSim
Gary Kronk's Comets and Meteor Showers:
http://comets.amsmeteors.org
includes historical info on the Leonids, and a special education corner with
online movies of comets, meteors and asteroids
Dr. Peter Jenniskens' Leonid MAC'99 Homepage:
http://leonid.arc.nasadot gov
includes details on the Leonid airborne mission, and excellent links to
other Leonid articles and sites
There are many ways to observe the Leonids. A lot of us will be making
visual observations with the unaided eye as we stretch out in lawnchairs
around the globe. A number of us will also be taking photographs - some with
elaborate multiple camera setups, and others with just a simple camera,
tripod and fast film. Still others will be training video cameras on the
skies, to capture Leonid meteors. All observations - no matter what kind -
are valuable in some way. Always remember though, to take careful note of
the start and stop times of your visual observations, photos or videos. Also
note that if you are observing in a group, do not combine your meteor counts
with those of other observers!
If you are just starting out to appreciate the sky, never think though, that
meteors can just be reduced to data and numbers! Meteors are a fascinating
phenomena of nature and can be appreciated in many different ways. Think of
all the old images in the astronomy books - the old watercolors, the
paintings, the sketches. They mean so much more in an aesthetic sense than
any column of numbers ever will. There are examples even in literature about
the wonder of meteor showers. The following poem is from one of my favorite
writers, the Robert Frost:
A Loose Mountain (Telescopic)...
Did you stay up last night (the Magi did)
To see the star shower known as Leonid
That once a year by hand or apparatus
Is so mysteriously pelted at us?
It is but fiery puffs of dust and pebbles,
No doubt directed at our heads as rebels
In having taken artificial light
Against the ancient sovereignty of night.
A fusillade of blanks and empty flashes,
It never reaches earth except as ashes
Of which you feel no least touch on your face
Nor find in dew the slightest cloudy trace.
Nevertheless it constitutes a hint
That the loose mountain lately seen to glint
In sunlight near us in momentous swing
Is something in a Balearic sling
The heartless and enormous Outer Black
Is still withholding in the Zodiac
But from irresolution in his back
About when best to have us in our orbit,
So we won't simply take it and absorb it.
It is interesting that Frost refers to the shower - at least in the title -
as telescopic. Although, yes, meteors will be seen in binoculars or
telescopes, this is a shower best appreciated with the unaided eye! Frost
even includes a reference to light pollution, which was very good of him!
The Leonids this year are an event not to be missed. Take some time off from
work and get out to observe on what could be several of the most memorable
nights of this century! Try to get some friends out. Show the skies and the
meteors to your children. They may object to the cold and the dark a bit,
but if the Leonids really put on a show, you will all remember it for many
years to come!
2. Other November Showers...
November also brings a number of other noted showers - such as the Taurid
meteors. The Southern Taurids (STA) reach a maximum on November 5th, with a
radiant at 052 degrees, ie. RA 03h28m, Dec +13, about halfway between the
horns of Taurus and the top of the head of Cetus. They can be seen until
about November 25th. Note that by mid-month, the STA radiant will have
moved much closer to Taurus, and will be about 5 degrees to the right of the
V. The Northern Taurids (NTA) reach a maximum on November 12th, with a
radiant at 058 degrees, ie. RA 03h52m, Dec +22, very close to the Pleaides
on the Taurus side. They can also be seen until about November 25th. Both
of these showers have meteors considered to be slow - the NTA's are about 29
km per second, and the STA's about 27 km per second. The ZHR for both
showers is about 5 meteors per hour at maximum. There is a group of objects
possibly associated with this meteor stream, as parent or sibling bodies,
including Comet Encke. The Taurid showers have been noted for their fireball
activity.
The Orionids (ORI), although having reached a maximum on October 21st, can
be seen until about November 7th. On November 5th, the radiant will be at
105 degrees, ie. RA 07h00m, Dec +17, which is about halfway between the
stars lambda and gamma Gemini, near the "left foot" of Gemini. These are
fast meteors, at about 66 km per second, and many of the meteors have trains
left behind. These meteors are debris from Halley's Comet.
The alpha Monocerotids (AMO) reach a maximum on November 22nd just before
the full moon on the 23rd. The radiant is at 117 degrees, ie. RA 07h48m, Dec
+01, about 4 degrees down from Procyon in Canis Minor. These meteors can be
seen from about the 15th to the 25th, and are quite fast at 65 km per
second. The rates for this shower have been variable in the past and always
warrant watching. In an average year, the ZHR rates at maximum are only
about 5 meteors per hour. However, this shower has experienced outbursts -
as in 1995, when rates soared to over 400 meteors per hour visible for a
short period of time.
Mention should be made of a particular minor shower not now on the IMO
working list, but which has been of note in the past. The Andromedids, often
called the Bielids, reach a weak maximum around November 14 to 17, although
activity may extend to early December. This is debris from Comet Biela.
Rates may be about 5 meteors per hour or less. The radiant is at
approximately 26 degrees, ie. RA 01h44m, Dec +37, between the close pair of
stars in Triangulum and the handle of Andromeda. The meteors atmospheric
velocity is quoted as 20 km per second. Back in 1872, a group of U.S.
observers recorded about 1,000 meteors an hour from this shower and
described them as being slower than Leonids and generally faint. Observers
in Italy saw over 33,000 meteors over about 6 1/2 hours. Rates in this
century have been very low. By 1904, rates were down to about 20 meteors per
hour. However, due to the fascinating outburst history of this shower, it
will always warrant some interest.
Lastly, there has been some talk lately about possible meteors from Comet
LINEAR (C/1999J3), centered on November 11th, but perhaps visible for a
number of days either side of that date. This comet has a long period,
estimated at about 60,475 years. Most of the meteor outbursts we have seen
through history have been due to short period comets that loop around us,
leaving particles and streams of debris with each passage. To get a good
display from a long period comet, which has not had as many opportunities to
shed its debris, is unlikely. However, it is still worth taking a look! If
there is any activity it should come from a radiant of RA 11h40m, Dec +53,
which is close to the star gamma Ursa Major, better known as Phecda or Phad,
the bottom left star of the bowl of the Big Dipper.
For use in judging the magnitudes of bright meteors seen this month, the
following are the magnitudes of the bright planets visible, as taken from
the Handbook of the Royal Astronomical Society of Canada:
On the 1st/11th/21st of the month:
Venus in the morning sky: -4.4, -4.3, -4.3
Mars in the evening sky: 0.7, 0.8, 0.8 (moving into Capricornus)
Jupiter all night: -2.9, -2.9, -2.8 (in Pisces)
Saturn all night: -0.5, -0.5, -0.4 (in Aries)
3. New Star Charts for Beginners...
We have just recently put some special star charts for beginners on the NAMN
website. They are a set of 4 maps covering the whole northern sky, showing
in simple form the constellations and their names, as well as the brightness
(magnitude) of a number of stars that can be easily used to judge the
brightness of meteors.
The latitude and longitude as it were in the sky, are given in Declination
and Right Ascension. The RA, Right Ascension, is shown using both the hour
units and the degree units, matching the coordinates used by the IMO, the
International Meteor Organization.
Many of the meteor websites provide a list of certain stars and their
brightness, but we have found that it is much easier for beginners if they
have some star charts right on their lap while observing! These also provide
a useful tool for learning new constellations, or refreshing your memory on
constellations that you haven't seen in a while.
What we recommend is that you print these off from the website at:
http://web.infoavedot net/~meteorobs
Change your computer print setup to "landscape" mode before printing. Then
put these charts into several heavy duty plastic page covers. You can then
use a black grease pencil, or something similar, to mark your meteor shower
radiants on the maps. The grease pencil rubs off easily with a tissue for
re-use during your next observing session. The plastic covers will also keep
your charts free from dampness due to dew or frost.
If you are interested in getting into serious observing and sending your
observations off to one of the meteor organizations, the NAMN website also
provides a link to the IMO limiting magnitude charts. These are a set of
charts giving particular areas in the sky for use in determining the
faintest star that your own eyes can detect - your "limiting magnitude."
It's not hard. The IMO has small maps of specific areas, with certain
triangles or 4-sided areas mapped out. What you do is pick one of these
areas (triangles are easier for beginners), and just count the number of
stars you can see in that area, including the corner stars. Then check the
chart that goes with that triangle, and it will show you something like "if
you counted 11 stars, then your limiting magnitude is 5.9." You can either
print off a couple triangle maps from the IMO site before going out
observing, or print yourself a whole set for reference if you are real
serious.
The NAMN website has many other resources as well. The NAMN Observing Guide
tells you how to get involved in meteor observing - what meteors are, and
what to record. You can read it on the website, or print it off for later
use. There are also a variety of forms available for your use in reporting
observations to NAMN.
4. Meteor Results from September...
September proved to be a month of slower activity, both in numbers of
meteors and numbers of observers reporting activity. Without a major shower
to its credit, September's activity consisted mostly of sporadic meteors,
with some minor shower members thrown in for good measure. About 65 hours of
observations over 16 nights were recorded by NAMN members.
Observers submitting reports in September include:
George Gliba Norman McLeod
Wayne Hally Scott Moser
Kevin Kilkenny Richard Taibi
Robert Lunsford Kim Youmans
Pierre Martin
This month we went back to the standard practice of having more sporadic
meteors reported than shower meteors. This is an interesting point to keep
in mind when you hear or read of the supposed pitfalls of monitoring meteor
activity away from the peaks of major showers. All of the periods are of
importance, and I urge members to consider expanding their observing
opportunities to include these "slower" times. The breakdown of reported
showers and number reported during September was:
Alpha Aurigids (7)
Aries-Triangulids (11)
Delta Aurigids (57)
Kappa Aquarids (1)
Kappa Cygnids (1)
Piscids (49)
Sporadics (621)
Delta Aurigids listed above include meteors reported as September Perseids.
Sometimes a source of confusion, the easiest way to explain this is to
consider the September Perseids as a branch of the Delta Aurigids, which
more properly, do not peak until October. NAMN follows the IMO guideline of
reporting all this activity as Delta Aurigid, but I have contacted the IMO's
Visual Commission Director for clarification, and hopefully a more
straightforward method of reporting members of this stream. The highest
hourly rate for this shower in 1999 was 5 reported by Kim Youmans in Georgia
on September 11/12 (0334-0447 EDT).
As reports began to come in from the middle part of the month, I anxiously
awaited word of whether any members of the Aries-Triangulid stream were
noted. As discussed in last month's issue, this is a shower that is in need
of many more observations as we are still trying to nail down what is truly
taking place. This year, eleven members were reported on September 11 and 12
by George Gliba, Pierre Martin and Richard Taibi.
Robert Lunsford in California had the highest Alpha Aurigid hourly rate of 2
on both the morning of September 1 (0330-0430 PDT) and September 7
(0430-0530 PDT). A nice display of Piscids appeared in September, with the
highest hourly rate of 4 going to Kim Youmans on September 10/12 (0307-0418
EDT).
I thank all of our observers for taking the time to submit reports of their
observations, and encourage everyone to make plans to observe the upcoming
activity in November and December.
5. Radio Observations of Meteors...
Over the past month we have received several letters and emails regarding
observing meteors with radio techniques. These have included how-to
questions as well as announcements of new software for reduction of such
observations. Since NAMN is primarily concerned with visual observations, we
have little information available dealing with radio techniques. For those
interested in checking out this worthwhile technique, the following websites
should serve as a start:
"Detection of Falling Meteors by means of Radio-Astronomy Techniques"
this site has how-to information, photos, specifications and diagrams.
http://users.skynetdot be/polard/meteor.htm
Radio Observations of Meteors, International Meteor Organization
this site contains introductory information, frequently asked questions,
references and software.
http://www.imodot net/radio/index.html
6. Upcoming Meetings...
January 10-13, 2000:
The 38th annual Aerospace Sciences Meeting & Exhibit of the AIAA, American
Institute of Aeronautics and Astronautics, will be held in Reno, Nevada. A
special session on meteors has been proposed, called 'Aerothermochemistry
effects in meteoric plasmas' and will be chaired by meteor astronomer Dr.
Peter Jenniskens of The SETI Institute at NASA/Ames Research Center, and
co-hosted by plasma physicists Dr. Olga Popova of the Moscow Institute for
Dynamics of Geospheres RAS and Dr. Iain Boyd of the Department of
Aerospace Engineering of the University of Michigan. This is an opportunity
for the plasmadynamics, thermophysics, and fluid dynamics communities to
learn more about the physics, aerochemistry, and optical diagnostics of
meteoroids. Information on the conference can be found on the website at:
http://www.aiaa.org/calendar/asm00cfp.html.
April 10-14, 2000:
IAU Colloquium 181 on Dust in the Solar System and Other Planetary Systems,
will be held at the University of Kent at Canterbury, in the United Kingdom.
This colloquium is the seventh in a series dedicated to studies of
interplanetary dust starting in 1967 in Honolulu, followed by Heidelberg,
Ottawa, Marseilles, Kyoto and Gainesville. The meeting comprises 15 or 16
sessions of around one-and-a-half hours duration with a review talk for each
topic and a limited number of 15 minute contributed papers as well as
posters. Scientific areas to be covered will include such topics as
Cometary Dust Modelling and Asteroidal Sources of Meteoroids, The
Interplanetary Dust Complex: Observations from Earth and Space,
Instrumentation for Dust Detection and Analysis, and many others.
Publication of the proceedings is planned after the meeting. Details are
available on the web at: http://wwwdot ukc.acdot uk/physical-sciences/space/
7. For more info...
Contact:
Mark Davis, MeteorObs@charlestondot net
Mt. Pleasant, South Carolina, USA
Coordinator, North American Meteor Network
And check out:
NAMN home page:
http://web.infoavedot net/~meteorobs
Back issues of NAMN Notes can be found on-line at the website.
To subscribe to the meteor email list or
To find out information on our weekly chat sessions:
Contact Lew Gramer at:
owner-meteorobs@jovian.com
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Here's to 'Clear Skies' for November!...
November 1999 NAMN Notes co-written
by Mark Davis and Cathy Hall
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