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(meteorobs) NAMN Notes: April 1999
I have been asked to post the entire issue, instead of just a pointer to the
URL. So here goes......Mark
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NAMN Notes: April 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 Lyrids!...
2. Other April Showers...
3. Meteor Email List and Chat Sessions...
4. Upcoming Meetings...
5. Canada's Biggest Star Party - Starfest '99...
6. NAMN and ALPO Results in Use...
7. For more info...
1. The Lyrids!...
April showers bring... the Lyrids! This year, the maximum, the date of
highest rates, is on April 22nd, at 16h UT, Universal Time, although shower
members (LYR) can be seen from about April 16th to 25th. The duration of
the peak itself is fairly narrow, with activity above 1/4 strength lasting
only about 2 days. The ZHR, zenithal hourly rate, is about 15 meteors per
hour with the unaided eye. This is variable, however - rates have been much
higher on occasion, such as 90 meteors per hour in 1982 for a brief period.
These meteors are average speed, at about 49 km per second. The radiant at
maximum is at 271 degrees, ie. RA 18h 04m, Dec +34, which is about halfway
between theta and nu Hercules, and not actually in the constellation of Lyra
at all. According to Kronk, the average magnitude, the brightness of the
meteors, is about 2.4, which is just a bit fainter than the main stars in
the Big Dipper. This makes it a good shower for both beginning and
experienced observers alike.
The Lyrids have been linked to Comet Thatcher, C/1861 G1. This comet was
discovered on April 5th, 1861, by A.E. Thatcher of New York at a magnitude
of 7.5 in the constellation of Draco, and according to Kronk, was described
as "a tailless nebulosity 2 arcmin in diameter with a central condensation."
The orbit of this parent comet was determined to be elliptical, with a
period of about 415 years.
The history of the Lyrid meteor shower can be traced back through historical
records to 687 B.C. It is the oldest shower to be mentioned in ancient
records. Outbursts, when there are much higher rates, have been seen in a
number of years including, in recent times, 1803, 1922, and 1982. Lovell, in
his writings, states that the many centuries the shower has been active is
"no doubt due to the high inclination (80 degrees) of the orbit which makes
planetary perturbations improbable." It is interesting to read about recent
attempts to determine the periodicity of the meteor stream. The orbit
determination relies heavily on photographic and radar results, which are
seldom obtainable every year - hence gaps in the data and our knowledge of
the shower. Studies of the years with higher Lyrid activity have found
however, that outbursts of fainter meteors occurred prior to the normal
meteor maximum.
The historical references to the Lyrids are interesting to read. A
newspaper in Richmond, Virginia on April 23rd, 1803, described the shower as
follows: "Shooting stars. This electrical phenomenon was observed on
Wednesday morning last at Richmond and its vicinity, in a manner that
alarmed many, and astonished every person that beheld it. From one until
three in the morning, those starry meteors seemed to fall from every point
in the heavens, in such numbers as to resemble a shower of sky rockets..."
Another published report lists an observer as having "counted 167 meteors in
about 15 minutes, and could not then number them all." Observers should
keep in mind that this shower is indeed capable of outbursts...
The Lyrids are the first main shower of spring. The moon is first quarter,
and the nights should be a little warmer for North American observers. So,
get out there observing - and clear skies to all!
2. Other April Showers...
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. On April
15th, just before new moon, the main radiant will be at 205 degrees, ie. RA
13h 40m, Dec -8, about 5 degrees up to the left of Spica in the
constellation Virgo. It should be noted however, that there are many
sub-branches of this ecliptic activity, with slightly differing radiants.
The ZHR rate is about 5 meteors per hour. These are just barely thought of
as medium speed meteors, with a velocity of about 30 km/sec.
Starting about mid-month, the Sagittarids (SAG) start to become active, and
will continue until mid-July. The radiant on April 15th will be at 224
degrees, ie. RA 14h 56m, Dec -17, about 2 degrees down to the left of the
star alpha Libra, affectionately known as Zuben el genubi, the "southern
claw." ZHR rates are low, about 5 meteors per hour. Just like the Virginids,
these just make it as medium velocity meteors, at about 30 km per second.
This shower has been associated with fireballs, even in old historical
references dating back to 354 A.D.
About April 19th, we can start to see eta Aquarids (ETA), which will reach a
maximum on May 6th. This is debris from Halley's Comet. The radiant on
April 20th, just before first quarter moon, will be at 323 degrees, ie. RA
21h 32m, Dec -7, about 1 degree below beta Aquarius, the star Sadalsuud.
ZHR rates at maximum will reach 60 meteors per hour, but rates we will see
in April will be low, leading up to that. These are fast meteors, at about
66 km per second.
The Pi Puppids (PPU) reach a maximum on April 24th, just past first quarter
moon, although they span the period from April 15th to 28th. The radiant at
maximum is at 110 degrees, ie. RA 07h 20m, Dec -45, which is about 15
degrees below eta, the left foot star of Canis Major, which is very low for
us in the northern hemisphere! The ZHR rate is listed as variable. Actual
observed rates reached 75 meteors per hour in 1977 in Australia. These are
nice, really slow meteors, at 18 km per second, making them ideal for
photographic attempts. The parent body is Comet 26P/Grigg-Skjellerup,
co-discovered by John Grigg of New Zealand in 1902 and by J.F. Skjellerup of
South Africa in 1922, 20 years later! It is believed that this comet was
also seen by Jean Louis Pons back in 1808. The period of the comet is about
5 years. The meteor shower is young, and has only been noted since 1972.
3. Meteor Email List and Chat Sessions...
Our meteor email list has just recently changed addresses! To get on the
list, contact Lew Gramer at: owner-meteorobs@jovian.com. Many thanks go
out to Lew for finding a new home for our meteor discussions, and for his
ongoing support to our cause!
For those newer persons not too familiar with our group, this is an
excellent meteor email list, administered by Lew Gramer, the Internet
Coordinator of NAMN. It is a worldwide email discussion list on the
observation and study of meteors. Whether you are interested in visual,
photographic, video, radio or other types of meteor observations, there are
both knowledgeable amateurs and professionals available on this list to
answer your questions.
The North American Meteor Network also continues to organize semi-weekly
online chat sessions on meteor observing. The chats are held Monday nights
starting at 8 pm EST (01:00 UT Tuesday), and Saturday mornings starting at
11 am EST (16:00 UT). These sessions can be joined by downloading a copy of
one of the many Internet Relay Chat programs (such as mIRC), and connecting
to the server on 'DALnet' known as: irc.daldot net. After connecting to
irc.daldot net, enter the IRC command: /join #namn. All interested persons
are welcome to join us!
4. Upcoming Meetings...
April 12-15, 1999:
The Leonid MAC Workshop is being held at the NASA/Ames Research Center,
Moffett Field, California. Its particular emphasis will be on the Leonid
Multi-Instrument Aircraft Campaign and related ground-based efforts.
Registration is available online at http://leonid.arc.nasadot gov/workshops,
and further information is available from Peter Jenniskens at
peter@max.arc.nasadot gov. The registration deadlines were Feb. 20th for
non-U.S. and March 1st for U.S. registrants. Sessions will cover such
topics as the role of meteors in life on earth, comet grain ejection and
meteoroid stream dynamics, meteoroid composition, meteor-induced atmospheric
chemistry, physics and chemistry of neutral atom debris, and observing plans
for the 1999 Leonids.
May 11-13, 1999:
The Leonid Meteoroid Storm & Satellite Threat Conference is being held in
Manhattan Beach, California. For more information, please contact
leonid-conf@aero.org or check out the website at:
http://www.aero.org/conferences/leonid. Papers are solicited in many areas,
including UV, optical, IR and radar observations of the 1998 Leonid storm;
dynamics, composition, occurrence of the Leonid meteoroids; and orbital and
meteoroid dynamics: 1997-2000.
July 26-30, 1999:
The Asteroids, Comets, Meteors 1999 Conference is being held at Cornell
University, near Ithaca, in New York State. Details are available at their
website: http://scorpio.tn.cornelldot edu/ACM. Although this is a professional
conference, a number of North American amateurs are planning to attend.
(NAMN members planning to attend, please also advise Mark Davis, NAMN
Coordinator, at MeteorObs@charlestondot net.)
August 7-15, 1999:
The 16th annual Mount Kobau Star Party, MKSP '99 will be held in southern
British Columbia, Canada, with talks and events on August 12, 13 & 14. Guest
speakers will include meteor researcher Dr. Martin Beech, a member of the
Canadian Leonid Team which sent an expedition to Mongolia last November. Dr.
Beech, will talk on Meteor Storms, Past, Present, and Future. Other speakers
include Gary Seronik from Sky & Telescope, Edmonton deep sky observer Larry
Wood, and astronomers from both the Dominion Radio Astrophysical Observatory
in Penticton and the Dominion Astrophysical Observatory in Victoria. For
more information, check out the website at http://www.bcinternet.com/~mksp
or contact the President of the Mount Kobau Astronomical Society, Jim
Failes, eij@bcinternet.com
September 23-26, 1999:
The 1999 International Meteor Conference (IMC), the annual conference of the
International Meteor Organization, is being held in Frasso Sabino, Italy.
The cost, including conference, lodging, and meals, is approximately $200
U.S. For more information, see the IMO website at http://www.imodot net
5. Canada's Biggest Star Party - Starfest '99...
Starfest, Canada's largest amateur astronomical convention, will be held
from July 15th to 18th this year in southern Ontario, Canada. This is a
camping star party with talks and events - bring your meteor gear,
telescope, and tent! In a typical year, about 1,000 observers attend this
outdoor convention coming from all over Canada and the States... so make
your plans today! For any of you in the U.S. northeast, it is just a short
detour...
There are a number of special talks this year on meteors, meteorites and
comets:
- Canadian meteor expert Dr. Peter Brown will talk on 'Prospects for a
Leonid Meteor Storm in 1999'
- Phil Gebhardt will give a talk on 'Radio Observations of Meteors'
- Dr. Richard Herd, Curator of National Collections at the Geological Survey
of Canada will give a presentation 'Meteorites', and discuss Canadian
meteorite research and recovery
- Dr. Paul Chodas, Research Scientist at NASA's Jet Propulsion Laboratory
will give several presentations: 'Calculating Orbits for Asteroids and
Comets' and 'Predicting Comet and Asteroid Impacts'
Other speakers at Starfest '99 will include:
- Ken Hewitt-White, a former RASC Ottawa meteor coordinator: 'Hitchhiking
Down the Cosmic Highway'
- Tim Puckett: 'The Puckett Observatory'
- Roger Hill: 'The $500 Canadian Observatory'
- Doug Cunningham: 'Quetican Observatory - The Spirit of Beautiful Places'
- Marc Castel: 'Building a Robotic Observatory - Design Considerations'
- Bryan Greer: 'The Hidden Truths: Thermodynamics and Telescope Design'
- Steve Dodson: 'For Your Eyes Only - Maximizing Your Scope's Output'
- Glenn LeDrew: 'Perfect Polar Alignment'
- Peter Ceravolo: 'Modern Astrographic Photography'
- Alan Dyer: 'Astrophotography Without Really Buying' and 'Coming Sky Events
for the Millenium'
- George Fazekas: 'Observatory Class Imaging System'
- Charles Sinsofsky: 'Digital Sky Image'
- Doug Clapp & Walter MacDonald: 'The Starlight MX5C - A One-Shot Colour
CCD Camera'
- Phil Keebler: 'Studying Eclipsing Binary Variable Stars with a Homebuilt
CCD Camera'
- John Hicks: 'The Approaching Solar Maximum'
- John Nemy: 'Astronomy Made Easy, Batteries Not Included'
Special activities include a children's astronomy program, swap table, and
many commercial vendors. The campground has all the amenities of home, as
well as a swimming pool and playground, to keep spouses and kids happy!
Many observers come up and stay for the whole week prior to Starfest to
enjoy the nice dark skies. Basic food service is available onsite during
the convention dates. There are also many nearby motels. For more info,
visit the website of the NYAA, North York Astronomical Association, at
http://www.interlog.com/~nyaa
6. NAMN and ALPO Results in Use...
The following is the abstract for a paper in Icarus entitled 'The Leonid
Meteor Shower and the Lunar Sodium Atmosphere' by D.M. Hunten (Univ. of
Arizona, Tucson), G. Cremonese (Osservatorio Astronomico, Italy), Ann L.
Sprague and R.E. Hill (Univ. of Arizona, Tucson), S. Verani (International
Space Science Institute, Switzerland), and R.W.H. Kozlowski (Susquehanna
Univ., Pennsylvania). Just an example of your NAMN and ALPO observations
being put to good use...
ABSTRACT
(ICARUS, August 1998)
Observations of lunar sodium were made on November 16-18, 1997 at Asiago
and Mount Lemmon Observatories. A small enhancement was observed, and we
suggest that it was related to the Leonid shower. Visual observations by
members of the Association of Lunar and Planetary Observers and the North
American Meteor Network show a peak, a few hours wide, at about 12:50 UT on
the 17th. The possible enhancement of the lunar Na appears to last at least
three days, and must be associated with a considerably more extended cloud
of particles than that responsible for the bright visual meteors. The
circumstances of the 1997, 1998 and 1999 events are discussed. Large showers
may occur in 1998 and 1999; the 1998 one occurs too close to New Moon for
good atmospheric observations, but if the extended, faint shower is also
enhanced the corresponding lunar Na should be observable for a considerably
longer period.
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.
======================================
Here's to 'Clear Skies' for April!...
April 1999 NAMN Notes co-written
by Mark Davis and Cathy Hall
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