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(meteorobs) NAMN Notes: March 2000
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NAMN Notes: March 2000
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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. March Showers...
2. Constellation Review - Ursa Major...
3. Xi Bootids Resolved into Two Radiants with
German Videos - by G.W. Gliba...
4. Recent Observations, February 2000...
5. Upcoming Meetings...
6. For more info...
1. March Showers...
March has no major showers, but several minor showers are visible. For
northern observers, it is finally starting to warm up so it is a good time
of year to start getting out more regularly, even if the rates are fairly
low. For beginners, it is a nice time of year to learn the sky better in
preparation for the busier summer months.
The minor showers visible that follow are those currently listed on the
working list of the IMO, the International Meteor Organization. Experienced
observers may wish, as always, to plot meteors in case other very minor
activity is present from other sources.
The Delta Leonids (DLE) reached a maximum on February 25th, but are visible
until about March 10th. At maximum, the radiant was at 168 degrees, ie. RA
11h12m, Dec +16, just about on top of the star theta Leonis, the bright star
Chort to the right of Denebola in Leo. By March 10th, the radiant (the
position in the sky where the meteors seem to come from) will have moved to
180 degrees, ie. RA 12h00m, Dec +12, just down to the left of Denebola.
These meteors are slow, with a velocity of about 23 km/sec. The ZHR,
zenithal hourly rate, was low even at maximum, with only about 2 meteors
visible per hour with the unaided eye, so rates in March will be extremely
low. Due to their slow velocity, however, these should be worth waiting for
- and are quite distinctive.
The Gamma Normids (GNO) reach a maximum on March 13th and are visible until
about March 22nd. The radiant at maximum is at 249 degrees, ie. RA 16h36m,
Dec -51, down to the right of the "J" of Scorpius, and possess a ZHR of
about 8 meteors per hour. Their velocity is slightly faster than average, at
56
km/sec.
The ecliptic meteor activity continues to be the Virginids (VIR), which
started in late January. This shower continues until about the middle of
April, with the radiant moving in position as the days go on. At the end of
February, the radiant was at 178 degrees, ie. RA 11h52m, Dec +03, near the
star beta Virgo, often called Zavijava, and by the end of March will have
moved to 198 degrees, ie. RA 13h12m, Dec -05, near theta Virgo. On March
10, 4 days past new moon, the radiant will be at 186 degrees, ie. RA 12h24m,
Dec 0, very near the star eta Virgo, known as Zaniah. The ZHR rate is about
5 meteors per hour. They are barely considered to be medium velocity meteors
with a velocity of about 30 km/sec.
For help in judging the magnitudes of brighter meteors seen this month, the
brightness of the planets visible are as follows, to the closest half
magnitude - Venus and Mercury are in the morning sky; Jupiter, Saturn and
Mars are all in the evening sky, and all in the constellation Aries.
Venus -4
Jupiter -2
Mercury +0.5
Saturn +0.5
Mars +1.5
New moon is on March 6th and full moon on March 20th. Actually, the skies
around new moon will be quite interesting in March. On the 8th, Mars will
be 5 degrees north of the moon, on the 9th, Jupiter 4 degrees north of the
moon, and on the 10th, Saturn 3 degrees north of the moon. About a week
later, on the 15th, at 0 hours UT, the moon will be at perigee (nearest the
earth) at a distance of only 369,533 km, and Mercury will be visible 2
degrees north of the planet Venus in the morning sky.
Starting about March 23rd, watch for the zodiacal light in the west after
evening twilight for the following two weeks for observers in northern
latitudes. Tropical observers are more fortunate, in that it is more easily
visible all year regardless of morning or evening sky. According to
the very handy reference book 'The Facts on File Dictionary of Astronomy' by
Valerie Illingworth: "The zodiacal light has been shown, spectroscopically,
to be sunlight scattered by minute dust particles in the interplanetary
medium in the inner solar system. The particles are concentrated into a
belt lying close to the plane of the ecliptic... It is shaped like a
slanting cone and extends from the horizon, tapering along the direction of
the ecliptic, and visible for maybe 20 degrees." Its visibility, brightness
and length will vary depending on where you are, and how dark your sky is.
As an aside, this softcover dictionary by Illingworth is an extremely handy
book for beginners. It has very easy to understand explanations of all
kinds of astronomical terms, including many we use in talking about meteors
and comets. And - it uses language everyone can understand.
Lastly, don't forget - if you need some handy star charts to mark this
month's meteor radiants on for use in the field, go to our NAMN website and
print yourself off a set! You might want to explore some of the other
resources on the site as well, such as the NAMN Observing Guide, which
answers many questions for beginners. Check us out at:
http://web.infoavedot net/~meteorobs
2. Constellation Review - Ursa Major...
Are you new to meteor observing, and trying to learn your way around the
sky, and the various terms such as meteor magnitude, degrees, limiting
magnitude, and RA and Dec?
We thought that a look at a familiar constellation might help to get you
started. So, let's look at Ursa Major, the Great Bear, which is probably
the most well known. If you live in northern latitudes, it's visible all
night, and is usually the constellation people first start with when
learning their way around the sky.
Ursa Major was identified with a large bear in ancient lore, not only by the
Greeks and Romans, but also by the North American Indian tribes. To the
ancient Greeks, the bear was originally Callisto of Arcadia, daughter of
King Lycaon, and a follower of the virgin goddess Artemis. Although sworn
to not love any man, this changed when she met the god Zeus, and she gave
birth to a son, Arcas. When the goddess Hera found out, she was furious,
and turned Callisto into a great white bear. Years later, when Callisto's
son Arcas was about to slay her while out hunting, Zeus came to her rescue,
and placed both of them in the sky so they would always be together -
Callisto as the Great Bear, Ursa Major, and Arcas turned into the Little
Bear, Ursa Minor.
The Big Dipper is the most familiar portion of the constellation Ursa Major.
The 7 stars of the Big Dipper, in order from the end of the handle to the
tip of the bowl, are as follows, listed by Greek alphabet designation (like
on a star atlas) and common name:
Greek Arabic Derived Name
Eta Alkaid, Benetnasch (Hindu Marici)
Zeta Mizar (with fainter companion Alcor)
Epsilon Alioth (Hindu Angiras)
Delta Megrez
Gamma Phecda
Beta Merak (Greek Helice, Hindu Pulaha)
Alpha Dubhe
In Hindu writings, these stars are names of sages or wise men. In ancient
Greece, Helice was the city where Callisto lived. In old Chinese writings,
the 3 stars of the handle of the Big Dipper are referred to as the "Jade
Scales," surmised as being a reference to measuring the seasons. In Welsh
legends, the name of King Arthur is claimed to come from Arth-Uthyr, "the
wonderful Bear." Every culture had its legends, and its own names for the
prominent stars of this constellation.
So, what can Ursa Major teach us about meteor observing?
For starters, you get your direction. If you follow on a straight line from
Merak to Dubhe ("the pointers") and keep on going, you bump into Polaris,
the North Star, which is the star currently closest to the North Celestial
Pole. Face Polaris, and you are facing north. However, it wasn't always
so. Back in Egyptian times, the "north star" was actually the star Thuban,
in the constellation of Draco. Further back, 12,000 years ago, the "north
star" was Vega in the constellation of Lyra.
Next, you can start to learn about meteor magnitudes or their brightness.
Ursa Major has several commonly used "standard" stars for judging meteor
brightness. The end of the handle, the star Alkaid, also called Benetnasch,
is commonly used as a magnitude 2. Remember - the bigger the number, the
fainter the meteor. Minus anything is bright. The brightest star in the
whole sky, Sirius, is a minus 1.5. A magnitude 5 is very faint. Alkaid, at
magnitude 2, is easily spotted, even close to a town or city, so it's quite
respectable.
The star Phecda, the lower left star in the bowl part, is used as a standard
2.5 magnitude. Some observers, like the Canadian co-author, like to use half
magnitudes. Sometimes it really helps to be able to call a meteor about
halfway between a 2 and a 3, so a 2.5 is useful.
Down below the handle of the Big Dipper are two stars in the constellation
Canes Venatici the Hunting Dogs. The dogs are named Chara and Asterion.
The two stars run about parallel to the bottom of the dipper's bowl, but are
down below the handle stars, about a bowl and a half's length down. The
star on the left is alpha Canes Venatici, better known as Cor Caroli, and is
used as a standard magnitude 3 for judging meteors. The name Cor Caroli,
"the heart of Charles" was used by Halley to honor King Charles II of
England.
Next, you can learn some lengths in the sky - degrees - by using the Big
Dipper. The distance between the pointer stars, Merak and Dubhe, is very
close to 5 degrees. So, you can use it as a measure in the sky for helping
find your way around, or measuring the length of a meteor. Practice holding
your outstretched thumb and forefinger at arms length to see what that
distance is for you in relation to the 5 degrees of the pointer stars.
Then you can do easy measurements of other places in the sky by using your
outstretched hand.
Now, let's determine your sky's "limiting magnitude," or the faintest star
that your eyes can detect on that particular night. Using the stars
Alkaid and Alioth in the handle of the Big Dipper, and the star Cor Caroli
down below the handle, count the number of stars that you can see in that
triangle. Include those 3 stars as well. This is called area 16 by the
IMO. Then use the following table (shown in part) to determine your LM, or
limiting magnitude:
#stars LM
4 4.6
5 5.1
6 5.7
7 5.9
9 6.0
11 6.2
13 6.3
14 6.4
For example, if you counted 6 stars, including the corner stars, then your
limiting magnitude is 5.7. If you counted 10 stars, then your LM would be
6.1. If you counted more than 14 stars, you have good eyes, and a good sky,
and should consult the full charts and tables on the IMO website at
www.imodot net.
Lastly, the Big Dipper gives you a reference for latitude and longitude in
the sky, which is called Declination and Right Ascension, usually
abbreviated as Dec and RA. The end of the handle of the Big Dipper is close
to 14 hours in RA. The pointers of the Big Dipper are at 11 hours in RA. In
Declination
(latitude in the sky) the Big Dipper stretches from about 50 degrees Dec
to about 62 degrees Dec. Do you have to remember these? No, this is just
to illustrate that the sky is just one big map with a grid system.
Some meteor groups do use a different sky grid though. The IMO lists Right
Ascension in degrees. Don't let it confuse you. RA in hours, multiplied by
15, equals degrees. In other words:
RA in hours RA in degrees
0 hours 0 degrees
2 hours 30 degrees
6 hours 90 degrees
etc.
So, if you see a meteor radiant listed as being at, for example, 170 +55,
you can convert that to the system used on your star map to figure out where
the meteors would come from, as follows:
1. 170 divided by 15 equals 11.33
2. which means 11 hours and .33 hours
3. which means 11 hours 20 minutes (.33 times 60 minutes in an hour)
4. result: RA 11h 20m, Dec +55 degrees
So, looking on a star map, this would be just to the left of the star Merak,
one of the pointers in the bowl of the Big Dipper.
In summary, you can learn a number of things useful for your meteor
observing just by examining a particular constellation, in this case Ursa
Major. Thanks for "bearing" with us, and if you have any questions, drop us
a line!
3. Xi Bootids Resolved into Two Radiants with German Videos - by G.W.
Gliba...
" Several experienced meteor observers from around the world have confirmed
the true nature of the Xi Bootid Meteor Shower. As mentioned before here,
and in the June 1997 Sky and Telescope, this minor meteor shower was
suspected on February 5/6, 1997, when I saw 14 meteors of medium speed in
2.5 hours coming from the area near the star Xi in Bootes during the Winter
Star Party in the Florida Keys. This area of the heavens was also watched by
me on the three following nights. In a total of 7.5 hours, from the morning
of February 5/6 to the 8/9, a total of 26 meteors were seen coming from this
suspected radiant in the constellation Bootes. The many visual observations
this year seemed to confirm this shower, but with the recent addition of 238
more video meteors, the Xi Bootids have now become an artifact, or false
radiant. This was due to the limitations of visual means to resolve the real
situation, which was that there were two new radiants close together, one in
Serpens Caput and another in Corona Borealis.
Two years ago, on the morning of January 25/26 1999, there were four
possible Xi Bootids meteors plotted, by Canadian meteor observer Pierre
Martin, from RA 13:55 DEC +22 in 1.6 hours, which seemed to be the first
confirmation that this putative shower was an annual one, and started in
late January. Pierre Martin is a veteran meteor observer for the North
American Meteor Network (NAMN), the American Meteor Society (AMS), and the
International Meteor Organization (IMO).
This year, ace meteor observer Bob Lunsford from Chula Vista, California
was out on February 1/2, and plotting meteors. Bob is the visual coordinator
of the AMS, Secretary General of the IMO, and a member of NAMN. Also, he
is the Recorder for the Association of Lunar and Planetary Observers Meteors
Section, and is the person most responsible for the recent revival of meteor
observing in this country a decade ago. He wrote recently to the NAMN
meteorobs newsgroup: "plots revealed no less than 5 areas in or near Bootes
that produced at least 3 meteors each. Four of the five are most likely
chance alignments. The other area may be confirmation of the Xi Bootids. An
area centered near 14:05 +16 produced 5 meteors with acceptable
velocities." This is a bit south of the projected Xi Bootid area, but within
a few degrees of it.
On February 2/3, Kim Youmans observed meteors from Treutlen Co, Georgia
and he plotted three faint medium-speed meteors in two hours that met at: 14
hrs 08 min +12, which is also close to Xi Bootis. Then on February 4/5, in
3.25 hours, he plotted another five dim medium speed meteors from a radiant
at: 14 hrs 09 min +14 in Bootes, a few degrees southwest of Xi Bootis. His
average LM was about 6.4 magn. On the same night, meteor observer Mike
Linnolt in Hawaii saw a couple of XBO meteors in an hour.
On the suspected night of maximum, February 5/6, the numbers of Xi Bootids
reported was the highest. From Hebei, China, Jin Zhu plotted at least six,
and possibly nine Xi Bootid meteors, with a LM of 6.0 magn. from 19:00 to
21:33 UT. Meteor observer, Javor Kac observed with Jure Zakrajsek from
Mariborska koca, Slovenia. He was able to plot at least three meteors from
near Xi Bootis. Jure Atanackov, also from Slovenia, saw several XBO meteors,
but from two radiants. He also plotted 7 others from a radiant at 14h 45m
+28, northwest of the main Xi Bootid region. Observing from Haleakala in
Maui, Hawaii, Mike Linnolt saw 14 XBO meteors from 14:40 +15 in 3 hours. In
one hour (1136 to 1238 UT) he saw 7 Xi Bootid meteors! Also out for the
peak, was the prolific meteor observer Kim Youmans of Georgia. In 3.07 hours
Teff, with 6.5 average LM skies, he was able to plot 9 XBO meteors from a
radiant near 14hr 11min +16, which agrees well with the location given by
Lunsford and Linnolt.
At the request of Bob Lunsford, IMO president Juergen Rendtel, in Potsdam,
Germany, included the Xi Bootids into the list for the automated video
meteor camera he has. Using Rainer Arlt's "Radiant" software, on the nights
February 3/4, 5/6 and 6/7, a distinct radiant was found near RA 15.26 Dec
+14, assuming a geocentric velocity of 50 km/s, based on 18 meteors. A
beautiful depiction of this new radiant is on the web at:
http://aipsoe.aipdot de/~rend/feb-boo.html. This is a very important, unbiased
confirmation observation. Another good video confirmation was made by Peter
Gural who, despite poor weather conditions, was able to record two Xi
Bootids on Feb. 5/6 in Northern Virginia.
In his own words, Kim Youmans wrote to the meteorobs list, addressing the
location of the Xi Bootid radiant, on Feb 8th he wrote: "After re-reviewing
my plots from the weekend, I do find a somewhat sharp radiant at RA 15.25
+14 involving 8 definite candidates and 2 potential candidates, based on
speed and path length. This is roughly two degrees right of and just below
the star Tau-1 Serpens. With five of the meteors, I need only a 2-degree
diameter circle to achieve the radiant. All eight definite candidates were
plotted on Feb 04/05 and 05/06. I reviewed my data after receiving J.
Rendtel's video-capture update/chart this morning on the IMO list. However,
when I "subtract out" the above eight meteors, at RA 15hr 15min +14, I am
still left with a radiant at roughly RA 14hr 09min +15 involving no less
than 5 definite candidates, and 2 potential candidates based on the same
speed data and path length, using plots from Feb. 03/04, 04/05 and 05/06.
This is an area roughly 2-3 degrees below Arcturus."
Later, after a total of 256 video meteors were seen by the German meteor
observers Juergen Rendtel and later Sirko Molau, the scatter in the visual
data makes more sense. It has been known for years that the accuracy of
manual visual meteor plots is not very good, as was illustrated by meteor
experts Millman and Porter in the 1950s, and explained in the book, Meteor
Science and Engineering by D.W.R. McKinley copyright 1961. Plus, random
scatter is even more inherent in visual meteor observing for low rate minor
showers. So, this scatter hinted that there was a problem with using only
the visual data. The real situation turned out to be interesting with the
addition of the data from videos. The Xi Bootids turns out to be an artifact
of the visual observations, and there are actually two nearby radiants, one
in Serpens Caput, and another in Corona Borealis.
Although only minor meteor showers, the combined total of meteors from the
delta Serpentids and Corona Borealids was strong enough to be seen from the
light polluted skies of Greenbelt, Maryland! I went out on Feb. 5/6, not
really expecting to see much. However, I was taken by surprise when, from 7
to 9 UT, I was able to plot five meteors from the area. Although they were
faint, with an average magnitude of only about 3.6, they were still
observable in the poor 5.3 LM skies. Although the limitations of the visual
observations did not allow the resolution of the two minor meteor showers
found by the videos, it was the enhanced activity first seen by visual
observers that was the catalyst to these remarkable new meteor shower
discoveries."
4. Recent Observations, February 2000...
The month of February saw fourteen observers submitting observations. At the
time of this writing, a total of 95.32 hours of observations were made on
fourteen separate nights or mornings. Some of the showers producing
activity, and the number reported in parenthesis, included the Alpha
Centaurids (10), Virginids (43) and the sporadics (788). Sixty-four meteors
were reported as members of the Xi Bootid radiant (see G. Gliba's article in
this issue) and are listed as such in the observing period report located on
our webpage. A total of 919 meteors were recorded in February.
Observers this month included Jure Atanackov (Slovenia); Peter Detterline
(Pennsylvania); John Drummond (New Zealand); George Gliba (Maryland); Javor
Kac (Slovenia); Mike Linnolt (Hawaii); Robert Lunsford (California); Michael
Mattiazzo (S. Australia); Scott Moser (Iowa); Trevor Pendleton (United
Kingdom); Dan Xia (China); Kim Youmans (Georgia); Jure Zakrajsck (Slovenia)
and Jin Zhu (China). Thanks to all observers for sending in your reports!
5. Upcoming Meetings...
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 7th in a series dedicated to studies of
interplanetary dust. Areas to be covered will include such topics as
cometary dust modeling, asteroidal sources of meteoroids, observations of
interplanetary dust from both earth and space, and instrumentation for dust
collection and analysis. Publication of the proceedings is planned after
the meeting. Details are available on the website at:
http://wwwdot ukc.acdot uk/physical-sciences/space/
April 16-19, 2000:
The Leonid MAC Workshop 2000 will be held in Tel Aviv, Israel. The workshop
focuses on studies of the Leonid shower, and will present the first results
of the Leonid MAC campaign and ground based program, as well as discuss
future efforts and opportunities for observing campaigns from 2000 to 2002.
The workshop aims to bring recent Leonid storm studies into focus and will
discuss recent progress made in understanding the satellite impact hazard,
the origin of life, new meteor, meteor train and meteor shower models,
sprites, impacts on the Moon, comet composition and ejection dynamics, the
spectroscopy of meteors and meteor trains, laboratory studies that help
explain the observed spectral features, remote sensing - new techniques that
may be deployed during future storms, and many other topics that relate
directly to the exploration of the Leonid showers. The registration deadline
is March 01. More information can be found at
http://leonid.arc.nasadot gov/workshops.
July 9-12, 2000:
The international conference 'Catastrophic Events and Mass Extinction:
Impacts and Beyond' will be held at the University of Vienna in Austria.
This is the 4th in a series of meetings on mass extinction and global
catastrophes, the previous meetings being 1981 and 1988 in Utah, and 1994 in
Houston, Texas. Expected topics include impact events in earth history,
boundary events in geologic time, environmental consequences of impacts,
interpretation of stratigraphic records, and extraterrestrial influences
such as asteroids and comets. The deadline for electronic abstracts is
March 3rd. More information on the conference can be found at:
http://www.lpi.usradot edu/meetings/impact2000/impact2000.2nd.html
July 25-August 4, 2000:
An International Astronomical Camp, IAC 2000, will be held in the Pohorje
Mountains at Mariborska koca (MBK), Slovenia. Work will be divided into
various groups - Solar System, Meteors, Deep Sky, Variables and double
stars, and Astrophotography. For more information, contact Jure Zakrajsek
by email at elizabeta.zakrajsek@guest.arnesdot si
September 11-15, 2000:
The international conference 'Space Protection of the Earth - 2000' will be
held in Evpatoriya in the Crimea. This is the 3rd in a series of
international conferences on the protection of the Earth from the threat of
its collision with asteroids and comets, with the prior meetings being held
in Saint Petersburg and Snezhinsk, Russia.
Topics will cover characteristics of asteroids and comets, their risk,
detection technologies, man-made means of influencing dangerous celestial
bodies, planetary defense, international cooperation, prospects for
utilizing asteroid and comet resources, and other issues. The deadline for
abstracts is March 1st. For more information, contact the SPE-2000 Program
Committee by email at: spe@asteroids.ru
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 NAMN website, and in
the meteorobs archives at:
http://www.tiacdot net/users/lewkaren/meteorobs
by selecting 'Browse Archive by Month'
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
======================================
Here's to 'Clear Skies' for March...
March 2000 NAMN Notes co-written
by Mark Davis and Cathy Hall
======================================
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