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(meteorobs) NAMN Notes: December 1999
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NAMN Notes: December 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. The Geminids...
2. Other Showers & Neat Things to Observe...
3. For New People Interested in Observing...
4. Meteor Results from October...
5. Upcoming Meetings...
6. For more info...
1. The Geminids...
The Geminid meteor shower is always one of the year’s best events. The
rates are good, are fairly dependable, and the meteors are usually bright
with nice trains. It’s a great shower for all observers, and especially for
new observers who may have joined us for the first time for the Leonids.
This year the Geminids (GEM) reach a maximum on December 14th at 11h
Universal Time, with a ZHR (Zenithal Hourly Rate), of about 120 meteors per
hour with the unaided eye. This is just before first quarter moon. The
Geminids last from about December 7th to 17th. The IMO, International
Meteor Organization, quotes this shower as being “one of the finest annual
showers presently observable.” This Canadian co-author has fond memories of
eight and nine hour winter nights spent enjoying this spectacular shower.
Dress warm - and you’re in for a treat!
The radiant, the position in the sky where the Geminid meteors seem to come
from, is located at 112 degrees, ie. RA 07h28m, Dec +33 at maximum. On a
star atlas, this is close to the bright star Castor in the constellation of
Gemini, the Twins. These meteors are of medium velocity at 35 km per second.
This is a good shower to observe both visually and to try some photographs
of!
The IMO, in their 1999 Meteor Shower Calendar, mentions that due to some
variability, the time of highest meteor rates may occur a bit before, or
more likely, a bit after the predicted time this year, perhaps from 15h to
16h UT, Universal Time on December 14th. The fainter telescopic meteors are
expected to be seen before the time of the highest visual rates. Never think
though, that good rates are only seen on one night - the nights before and
after can be just as rewarding.
The Geminids have as their parent body the asteroid 3200 Phaethon. This
was announced by the IAU, the International Astronomical Union, in 1983, and
was the first time an asteroid - as opposed to a comet - had been linked to
a meteor shower. In most cases, it is comets that are the parent bodies,
with particles of debris being shed each time they go through our solar
system. However, over time, comets can be depleted of material, and
approach a more “asteroidal” like state. Actually, it is interesting to
read some of the details on this shower in the IMO Handbook. Some
investigators say that Phaethon is the largest remnant of the parent of the
Geminid stream, and that it is still unclear what the true “parent” was.
Reports of the Geminid shower go back only to the 19th century. The IMO
states that “the first indications of the Geminid meteor shower were
published by the early Belgian meteor researcher Quetelet (1841, 1861), who
mentioned high meteor activity on 1830 December 12-13 at Heiligenstadt
(Germany), from where 40 fireballs were reported.” However, computer
simulations studying the characteristics of the shower, and the sorting of
the particle debris, seem to indicate activity going back much further.
2. Other Showers & Neat Things to Observe...
The Chi Orionids (XOR) reach a weak maximum on December 2, just past last
quarter moon, with a radiant at 082 degrees, ie. RA 05h28m, Dec +23, about 5
degrees south of Beta Auriga. They have a ZHR rate of about 3 meteors per
hour, and are considered slow with a velocity of 28 km per second. However,
in spite of the low rates, observations (in particular from Australia) have
shown these meteors to be fairly bright, with an average magnitude of about
1.60, with about 14% producing trains, and over 30% of the meteors showing a
yellow color. The IMO lists this shower as being weak visually, but
moderately active telescopically. The Chi Orionids are considered to be a
continuation of the Taurids, and have occasional fireballs. They can be seen
until about the 15th of the month. As an aside, if you happen to have your
telescope out with you as well while observing on December 3rd, the planet
Mercury reaches its greatest elongation, 20 degrees, at 01h UT, very
favorable for observers in northern latitudes.
The Monocerotids (MON) reach a weak maximum on December 9, just past new
moon, with a radiant at 100 degrees, ie. RA 06h40m, Dec +08, just south of
the left foot of Gemini. They have a ZHR rate of about 3 meteors per hour,
and are medium velocity at 42 km per second. They can be seen until about
December 17th. It is believed that this shower is associated with Comet
Mellish, D/1917 F1, with an orbital period of about 145 years. This shower,
according to recent studies, may also be the source of many of the
spectacular fireballs of the eleventh century. Many of these are documented
in the writings of Ma Touan-lin, a historian of the pre-Mongolian era, who
collected observations of over 1,500 fireballs going back over 24 centuries!
The Sigma Hydrids (HYD) reach a weak maximum about December 12th, about
halfway between new moon and first quarter, with a radiant at 127 degrees,
ie. RA 08h28m, Dec +02, off to the left of Procyon in Canis Minor, south of
the little circlet of stars at the top of Hydra. They have a ZHR rate of
about 2 meteors per hour, are fast with a velocity of 58 km per second, and
in recent years, have shown an average magnitude of +3 or fainter. A large
percentage have trains. These meteors can be seen until about mid-month.
The Sigma Hydrids were first detected by photographic means in the 1960’s.
According to the IMO notes on this shower for 1999, “recent data indicates
the peak may occur up to six days earlier than suggested above, and would
benefit from visual plotting, telescopic or video work to pin it down more
accurately.” Get out your plotting sheets!
Actually, December 12th would be an interesting night to bring your
telescope along as well. There is an occultation of the planet Mars
centered on 19h UT on December 12th (according to the Canadian RASC
Handbook), visible in northeastern South America, the eastern United States
(crossing the top of New Jersey!), Central America, northwest Africa, the
British Isles, and western Europe. The graze and occultation data provided
by E. Riedel and D. Dunham for the Handbook list the visual magnitude of
Mars at that time as 1.1, the moon as 19% sunlit, a northern limit track, UT
at the west end of the track as 17h29.1m, and longitude and latitude of the
west end of the track as -90 degrees and 45 degrees. Central South America
will be treated to an occultation of Uranus several hours later.
The Coma Berenicids (COM), reach a maximum on December 20th, several days
before full moon, with a ZHR rate of about 5 meteors per hour. This shower
lasts from about December 12th to January 23rd. The radiant on December
20th is located at 175 degrees, ie. RA 11h40m, Dec +25, which is about 10
degrees north of the bright star Denebola in the triangle of Leo. These
meteors are fast with a velocity of 65 km per second. This shower is quite
possibly associated with Comet Lowe, 1913 I, discovered by an amateur
astronomer in South Australia.
Lastly, the Ursids (URS) reach a maximum on December 22nd with a ZHR rate of
about 10 meteors per hour. This is just about at the time of the largest
full moon of 1999, which occurs at 17h31m UT on December 22nd when the moon
also reaches its closest perigee distance of the year at 356,653 km. On
occasion this shower has surged up to about 50 meteors per hour, so it is
worth watching in spite of the very large moon. The radiant is located at
217 degrees, ie. RA 14h28m, Dec +76, which is just above the “pointer stars”
of Ursa Minor, the Little Dipper. The Ursids are medium velocity at about 33
km per second, and tend to be faint. They can be seen from about December
17th to 26th. The Ursids bear an association with Comet Mechain, now called
Comet Tuttle. Pierre Mechain of France discovered the comet on January 9,
1790, but there were not enough observations of it to discover its periodic
nature. It was recovered on January 5, 1858 by Horace Tuttle of
Massachusetts, and given his name instead. Luckily, the shower itself is
named after the constellation, Ursa Minor!
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: -4.2, -4.2, -4.1
Mercury in morning twilight: -0.4, -0.5, -0.5
Mars in evening twilight: 0.9, 0.9, 1.0 (in Capricornus)
Jupiter most of the night: -2.8, -2.7, -2.6 (in Pisces)
Saturn all night: -0.4, -0.3, -0.2 (in Aries)
3. For New People Interested in Observing...
Welcome to all the new observers who may have come out for the Leonids! We
hope you got some good skies, and that your interest in further meteor
observing may have been sparked by all the enthusiasm surrounding this
rather unusual event this past month.
You might be giving some thought as to how to get more involved in our
amateur meteor community, and make some more observations. So, how do you
get more observing in, and get involved?
Check to see if there is a local astronomy club in your area. Check the
phone book, or contact the local observatory or planetarium. The ASP,
Astronomical Society of the Pacific, has a listing of many local clubs on
their website at: http://www.aspsky.org/links/clubs.html Sky & Telescope
magazine also maintains a list of clubs at their website:
http://www.skypub.com/
You could also post a message to our meteor email list by contacting Lew
Gramer at owner-meteorobs@jovian.com to ask if there is an astronomy group
nearby. The advantage of observing with a group is that they may have a
dark sky site or observatory outside town where you could meteor observe
from, and perhaps even meet other people with similar interests.
Observing in a group, especially in the colder winter months, is safer. You
have somebody else there in case of emergency, and talking to observing
buddies during the night keeps you more alert. In the case of students,
your parents are much more likely to let you go out observing if they know
you are safe with an organized group with a couple of adults present.
Observing all by yourself is fine as well of course, but take proper safety
precautions. If you are fortunate enough to have your own backyard
with moderately dark skies, then you are all set!
Where do you get information on what to record? Probably the best single
source of information for beginners is our NAMN Observing Guide. It is
available online, free of charge, at: http://web.infoavedot net/~meteorobs
What do you need to get started in meteor observing? The basic equipment is
as follows - although there are many variations used by different observers
around the globe:
For comfort, get yourself a reclining lawnchair so that you don’t have to
lie flat on the ground. Use a sleeping bag for warmth, and a foam mat
underneath your sleeping bag. This provides important insulation below your
body, where both your clothes and sleeping bag are compressed. A survival
tarp over your sleeping bag will protect you from dew, frost and wind. If
you have problems in your area with ground-based animals, try to observe
from an elevated area, such as the back of a truck, or the rooftop of a
building, or at least a secure fenced in area.
Wear warm clothes, as this is winter for us in the northern hemisphere. A
good hat is important, as the body loses the most heat through the head.
Many of us wear balaclavas, with openings just for our eyes and mouth. Good
gloves and socks are important, as your extremities will feel the cold more.
Take spare gloves and socks - often what you think will be warm enough, is
not.
For observing, take a red flashlight to read your star charts without
destroying your dark adaptation. Some red plastic over the end of a
regular flashlight works well. Take some pencils, and an accurate watch to
note the time of each meteor. Many observers use a pocket tape recorder,
although paper and pencil is fine for slower nights, and is always
recommended as a backup. Most of us try to use a short-wave radio to set our
watch or clock before we leave home to go observing. A thermos of your
favorite hot beverage or late night snack, is a good idea. Even if you don’t
drink while observing, it is sure nice to have something warm at the end of
the night. Lastly, depending on your observing site, insect or animal
deterrents such as FM radios may be needed.
A set of four beginner star maps, both to find your way around the
constellations, and to judge the brightness of the meteors you see, can be
printed off from the NAMN website (under "Star Charts") at:
http://web.infoavedot net/~meteorobs/charts.html
The NAMN site also has its own sheets to record your meteors on (under
"Observing Report Forms"), printable from:
http://web.infoavedot net/~meteorobs/namn_form.html
What showers are visible? The NAMN site has a list of showers, and our
monthly newsletter provides more detailed info on these showers.
Limiting magnitude charts, to estimate how faint you can see, and determine
how good your skies are, can be printed directly from the IMO website at:
http://www.imodot net/visual/major01.html#table2 See what constellations are up
for your time of year, and print off several charts before going out for
your night of observing. You just count the number of stars you can see in a
given area, and it tells you what your faintest visible star is! There is
also a direct link from the NAMN "Star Chart" section to the IMO limiting
magnitude charts.
For reducing your data at home after your observing is finished, details on
filling out a manual report are given on the NAMN website in the NAMN
Observing Guide. Alternatively, the IMO has a computer program on their
website that can be downloaded free of charge and generates your meteor
report for you! (It is, however, very wise for beginners to read the NAMN
Guide first to understand the terms used, and perhaps try doing some manual
reports as well.) This IMO program is called VisDat, and although primarily
intended for measuring visual meteor plots, will also produce reports of
counted meteor data. The advantage of this program is that your data will be
in a format easily archived by the International Meteor Organization, and
easily accessible to meteor researchers! More details on this program will
be included in a future issue of NAMN Notes. VisDat can be found on the IMO
website at: http://www.imodot net/software/visdat/index.html
Meteor observing is one of the very few fields in astronomy where amateurs
can make valuable contributions - with very little equipment required for
visual observing. This is what makes it such a rewarding area of astronomy
for beginners. You don’t need elaborate or expensive equipment, or even
binoculars or a telescope. You can just use your own eyes! We hope that
many of you who came out to watch the Leonid shower in November will
continue your interest in observing meteors. It is an enjoyable pastime,
and one of the few fields in astronomy where amateurs can really make a
difference!
4. Meteor Results from October...
The highlight for October had to be the Orionids, although some observers
had high hopes for activity from the Giacobinids (Draconids). The Delta
Aurigid and Taurid streams remained active during the month, and were joined
by the Epsilon Geminids. In all, 14 observers submitted reports covering 21
nights in October. This provided a little more than 92 hours of
observations. Reports were received from the following observers:
Joseph Assmus Pierre Martin
Mark Davis Michael Mattiazzo
Peter Detterline Norman McLeod
George Gliba Wes Stone
Wayne Hally David Swann
Kim Hay Richard Taibi
Robert Lunsford Kim Youmans
The Giacobinids are active between October 6 and October 10, with a peak of
October 9. Not expecting to produce much activity this year, only 5
observers kept an eye on the sky while they were visible. Mark Davis, Wayne
Hally and Pierre Martin reported none during their observations, while Peter
Detterline and Kim Youmans reported 1 each on October 7/8 and 8/9
respectively.
The Delta Aurigids produced only 23 meteors for observers this month - the
highest rate in one hour being 4 as reported by Peter Detterline on October
18/19 (0800-0900 UT). Five observers, including Peter Detterline, Robert
Lunsford, Norman McLeod, David Swann and Kim Youmans reported rates of 2 per
hour during several watches in October.
The Epsilon Geminids were the second most active shower of the month with 48
members reported. The first one of the year was reported by Kim Hay on Oct
11/12 when she saw 2 during the period 0718-0835 UT. The highest hourly rate
this year came on October 19/20 for Wes Stone when he saw 5 from 1030 to
1130 hours UT.
A steady rate of Taurids were also reported in October, with 41 reported
from the Southern branch, 28 from the Northern, and 12 combined into one and
listed as Taurids. Most observers reported only 1 or 2 per hour total. The
highest hourly rate occurred on October 19 when Robert Lunsford saw 5
Southern Taurids and 1 Northern Taurid between 0815-0922 hours UT.
As mentioned above, the Orionids were the highlight for the month, and with
501 meteors being recorded, produced about 40 percent of the activity in
October. The first Orionid of 1999 appeared on October 6/7, and over the
next week, observers reported at most 1 or 2 per hour. An increase was then
seen beginning October 13/14 when their hourly numbers doubled and sometimes
tripled (3-7 per hour) up until near the peak period - October 20/21. Clouds
prevented many observers from being out that morning, so only a handful of
reports were received. A sample of these reports and their rates include
George Gliba (13 Orionids between 0800-0900 UT), Richard Taibi (11 Orionids
between 0753-0935 UT) and Wes Stone (6 Orionids between 1045-1145 UT). The
highest hourly rate reported for October 20/21 was Pierre Martin’s 19
Orionids between the hours of 0720-0859 UT. It is interesting to note
however, that matching the rate of 19 on October 20/21, were the reports of
Wes Stone and Robert Lunsford, who on the preceding day (October 19/20),
also reported 19 Orionids each during the hours 1030-1130 UT and 1145-1245
UT respectively. Topping all of these though, was the report of Kim Youmans
from October 21/22 where he observed 21 between 0900-1003 hours UT.
In all, 1,239 meteors were recorded during the month of October. The showers
reported, and the number observed follows:
Delta Aurigids (23)
Epsilon Geminids (48)
Giacobinids (2)
October Arietids (9)
Orionids (501)
Piscids (1)
Taurids (combined) (81)
Sporadics (574)
At the present time, reports are still arriving from our Leonid campaign,
which was a great success. It is possible the review will be completed prior
to the next issue of NAMN Notes. If so, a separate summary will be emailed
out, followed by the January issue the first week of the new year.
Otherwise, the Leonid review will arrive as part of the next issue.
Thanks to all the observers for sending in their reports from October! I
look forward to hearing of your success during the Geminids, and wish each
of you a warm and happy holiday season.
5. 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 Modeling 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/
September 21-24, 2000:
The IMC, International Meteor Conference, of the IMO, the International
Meteor Organization, is being held in Pucioasa, Romania, about 100 km
northwest of Bucharest. It is being organized by the Romanian Society for
Meteors and Astronomy (SARM), in cooperation with the mayoralty of Pucioasa.
Pucioasa can be reached by direct trains and buses from Bucharest, and a
shuttle bus from the Bucharest airport to the conference site is planned.
Accommodation will be provided in double rooms, and meals served at the
restaurant of the hotel close to the conference site. The conference fee
will be 170 DEM. A deposit of at least 100 DEM is requested for those
interested in attending, and a registration form is on the IMO website at
www.imodot net.
6. 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 December...
and a ‘Merry Christmas’ to all!
December 1999 NAMN Notes co-written
by Mark Davis and Cathy Hall
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