(meteorobs) NAMN Notes: September 2004

Sat Sep 4 06:58:07 EDT 2004

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NAMN Notes:  September 2004
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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://www.namnmeteors.org

Contents:

1.  September Meteors from Auriga...
2.  Aries-Triangulid & September Taurid Meteors... by G.W. Gliba
3.  Other September Showers...
4.  Upcoming Meetings...
5.  For more info...

1.  September Meteors from Auriga...

September brings the start of our fall season - and 'falling stars' from the
constellation of Auriga!  The nights are starting to cool off, the
mosquitoes are starting to dissipate, and the evening skies are quite
enjoyable.  Try to get out and take in some of our fall showers.

The alpha Aurigids (AUR), although having reached a peak on August 31st, can
be seen until about September 8th.  These are fast meteors, at about 66 km
per second.  The radiant at maximum on the 31st was at 084 degrees, ie. RA
5h 36m, Dec +42, which was about 5 degrees to the left of the star eta
Auriga, the star known as Hoedus II, 'the Charioteer's 2nd kid goat'.  A map
of the radiant showing its movement over the week can be found at
http://www.imo.net/calendar/cal04.html#delta-Aurigids.  ZHR rates at the
peak were about 7 meteors per hour, but will be less in September.

What is ZHR?  ZHR stands for Zenithal Hourly Rate, and is the average number
of meteors that an observer would expect to see in an hour, if they are out
under a dark country sky, and if the radiant, the area in the sky where the
meteors seem to come from, is directly overhead.

The delta Aurigids (DAU) can be observed from about September 5th through
until about October 10th - and reach a peak on September 9th.  These are
also fast meteors, with a velocity of about 64 km per second.  ZHR rates at
the peak will be about 5 meteors per hour.  The radiant will be at 060
degrees, ie. RA 4h 00m, Dec +47, which is about 3 degrees to the left of the
star delta Perseus.  Note that meteor shower radiants do move - and are not
always in the constellation they are named after on any given night!  Check
out the map at http://www.imo.net/calendar/cal04.html#delta-Aurigids to see
exactly where the radiant for the delta Aurigids will be on the nights you
are headed out observing.

According to the IMO, the International Meteor Organization, on their
website at http://www.imo.net:

" A detailed, fresh analysis of the low-activity, and little-studied,
delta-Aurigids was carried out by Audrius Dubietis and Rainer Arlt using IMO
data from 1991-2001 in 2002.  This demonstrated the shower probably
represents a combination of two separate, but possibly related, minor
sources, the September Perseids, for which the maximum time given above
holds, and the delta-Aurigids, whose activities and radiants effectively
overlap one another.  The showers are probably not resolvable by visual
watchers, who are advised to retain the, slightly amended, shower parameters
listed above.  The actual delta-Aurigid phase seems to give a weak maximum
around sol = 181 degrees (2004 September 23; ZHR 3, r=2.5).  The shower is
essentially a northern hemisphere event, and it needs to be noted that there
is a series of poorly observed radiants in or near Aries, Perseus,
Cassiopeia and Auriga, active from late August to October... "

" Telescopic data to examine all the radiants in this region of sky - and
possibly observe the telescopic beta-Cassiopeids simultaneously - would be
especially valuable, but photographs, video records and visual plotting
would be welcomed too. "

If you want to record data on these showers for the meteor researchers,
check out our NAMN Observing Guide for information on what to record.  Our
Guide can be found at http://www.namnmeteors.org/guide.html.  We record such
info as the time a meteor occurred, its magnitude (brightness), the shower
it belongs to, its speed, and other comments such as train left behind, or
color.  General information to record includes such things as how dark your
perceived sky is (limiting magnitude), and comments on weather and cloud
cover.  For estimating the brightness of the meteors you see, we have a
handy set of 4 star charts (set printer to 'landscape mode') at
http://www.namnmeteors.org/charts.html.  If you have any questions, drop a
note to our NAMN Coordinator at meteors at comcast.net

Forms to record your observations can be found at
http://www.namnmeteors.org/namn_form.html and
http://www.namnmeteors.org/appendixC.html.

Auriga is a wonderful fall constellation - and also a very interesting one
to observe under a dark country sky.  There are a number of large star
clusters visible to the unaided eye, and they are wonderful to explore in
binoculars as well.  For an online map showing these clusters,
check out the website of the Hawaiian Astronomical Society at
http://www.hawastsoc.org/deepsky/aur/index.html

Auriga is the Charioteer in the heavens.  He is sometimes identified with
Phaethon, the son of Helios, the sun god. Apparently Phaethon wanted to make
sure that Helios was really his father.  Helios said yes, he was his father,
and to prove it, let him drive his sun chariot across the heavens for a day.
The chariot was hard to handle, the horses balked, and Phaethon lost
control.  The chariot careened into the northern sky, and Zeus hurled a
thunderbolt to stop it.  Phaethon was struck down by the lightning and
died.  The Charioteer, Auriga, remains in our northern sky...

Get out and take in some September skies.  Auriga awaits... and we could use
your observations of these interesting fall meteor showers!

2.  Aries-Triangulid & September Taurid Meteors... by G.W. Gliba

There might be some significant activity visible from the Aries-Triangulid
minor meteor shower (a.k.a. alpha Triangulids) expected this year.  The
maximum should be on September 12th or 13th.  There is some historical
evidence that this stream may be periodic, and that this year may be a more
active one than usual.  The primary radiant appears to be near alpha
Trianguli, with a possible secondary radiant located further south near the
2nd magnitude star Hamal (alpha Arietis).

Historically, this shower seems to have a period of 5 or 6 years, according
to comet and meteor researcher Gary W. Kronk.  The last years with good
activity were recorded in 1998 and 1999.  The other known years, when two or
more experienced meteor observers saw good activity visually, were in 1934,
1940, 1951 and 1993.  So, it is possible that enhanced activity might be
seen this year.  Also, lunar conditions are very favorable and the peak
occurs on a weekend.  Some activity has been reported every year since this
meteor stream was first discovered to be possibly annual eleven years ago.
Although the IMO (International Meteor Organization) does not officially
recognize this minor meteor shower, it is on the ALPO (Association of Lunar
& Planetary Observers) Meteor Shower List.  Gary Kronk also mentions this
minor meteor shower on his 'Comets & Meteor Showers' website at
http://comets.amsmeteors.org/meteors/showers/aries_triangulids.html

The September 2004 issue of Sky & Telescope magazine has an article on the
September Taurid shower, which is another possible minor meteor shower which
peaks near September 14th.  However, there is more controversy as to its
existence than the above shower due to its close proximity to the northern
and southern apex meteor sources, which are nearby, and thus a source of
meteor pollution.  Last year in WGN (originally Werkgroupniews), the Journal
of the IMO, 31:3 (2003), an article on the existence of this putative minor
meteor shower, explains that according to Arkadiusz Olech, visual meteor
data from the Polish Comets and Meteors Workshop group shows no trace of
September Taurid meteors from 1996 to 2000.  They do mention another less
plausible explanation, that this meteor shower might be real but not present
during 1996-2000.

Interestingly, the Polish Comets and Meteors Workshop data mentioned in this
article clearly shows activity from the Aries-Triangulum area!  So, this
year is a good one to try to resolve the meteor activity situation for these
suspected minor meteor showers in the late summer morning skies.

(Thanks to George Gliba for providing details on these showers.  Questions
can be directed to him at gliba at milkyway.gsfc.nasa.gov)

3.  Other September Showers...

For any given month, there are always meteor showers to be observed and
studied!  Different organizations often study different showers though, and
even define some showers in different ways.

NAMN, our North American Meteor Network, follows the 'Working List of Visual
Meteor Showers' of the IMO, the International Meteor Organization, with
their website at http://www.imo.net.  As noted in George Gliba's article
this month, the Aries-Triangulid minor shower is on the ALPO list.  An
interesting history of that minor shower can be found in Gary Kronk's Meteor
Observing Calendar at http://comets.amsmeteors.org/meteors/calendar.html.
The possible September Taurids, on the other hand, as Gliba has noted, are
more controversial.  And - the 'apex' meteors referred to are discussed in
more detail in 'Robert Lunsford's Weekly Meteor Outlook', on the web at
http://amsmeteors.org/lunsford

It should be noted as well that new research papers are always coming out.
A paper recently discussed on the MeteorObs email list was 'Meteor Outbursts
from Long-Period Comet Dust Trails' by E. Lyytinen and P. Jenniskens.  It
discusses the possibility of meteors on September 11th around 18h UT from a
radiant near epsilon Eridanus, at 056 degrees, ie. RA 3h 43.8m, Dec -14.
The paper provides a working list of far-comet type meteor outbursts from
2003 through until the year 2050.  Check out the full paper at
http://aio.arc.nasa.gov/~leonid/ICARUSLP-final.pdf

Continuing with showers on the International Meteor Organization's 'Working
List of Visual Meteor Showers', we have the following activity in September,
in addition to the alpha and delta Aurigid showers discussed earlier:

The Piscids (SPI) reach a peak on September 19th, but can be seen all
month.  These are slow meteors, at about 26 km per second.  The radiant at
the peak on the 19th will be at 005 degrees, ie. RA 0h 19.8m, Dec -01, which
is about 15 degrees south of gamma Pegasus, the bottom left star of the
Great Square of Pegasus.  ZHR rates at maximum will be about 3 meteors per
hour.  A map showing the radiant throughout September can be found at
http://www.imo.net/calendar/cal04.html#piscids.

According to the IMO, "Audrius Dubietis carried out an examination of
IMO data on the Piscids (earlier known as the Southern Piscids; no other
Piscid radiant has been clearly defined as visually active for many years)
between 1985-1999 in early 2001, which essentially confirmed the current
details on it are correct, including that this is another poorly observed
minor shower!"

The Sextantids, a daytime meteor shower normally detected by radio
observers, could yield some visual meteors in late September.  The maximum
is expected on September 27th at 3h UT, according to the IMO, the
International Meteor Organization.  It may occur a day earlier though.
Yet - a strong return was observed in 1999 at a time coinciding with this
year's September 28th.  Try to observe around these nights to check it out.
The radiant on the 27th is listed as 152 degrees, ie. RA 10h 7.8m, Dec 0.
Our NAMN star charts can be used to plot these coordinates on - print them
off from http://www.namnmeteors.org/charts.html

Besides September's main activity, and other minor showers, there is also
sporadic meteor activity - about 7 meteors per hour, visible to the unaided
eye.  Some of these are random, and some belong to old untraceable meteor
showers.

Planets at midmonth, and their magnitudes, for northern observers, are:
Venus      -4.2   very bright in east in morning sky
Saturn      0.2   in Gemini, in morning sky
Mercury    -0.5   very low in east in morning sky

On September 10, Mercury will be 0.06 degrees south of the star Regulus, and
Venus 7 degrees south of the moon - so the morning sky, with Saturn as well,
will be very nice indeed!  To see a map of your sky with all the visible
planets marked, check out the website of 'Heavens Above' at
http://www.heavens-above.com

This month, the phases of the moon are as follows:
Mon.  Sept.  6    last quarter
Tues. Sept. 14    new moon
Tues. Sept. 21    first quarter
Tues. Sept. 28    full moon
For a great printout of moon phases for the month, check out
http://stardate.org/nightsky/moon

4. Upcoming Meetings...

September 23-26, 2004, Varna, Bulgaria...
The IMC, the International Meteor Conference of the International Meteor
Organization, is being held this year in Varna, Bulgaria.  Varna is often
called the 'sea capital' of Bulgaria due to its location on the Black Sea.
The conference will be held at the Chayka resort, about 10 km outside the
city, and participants housed at the Varna Free University.  The IMC is the
worldwide meeting for meteor observers - both amateurs and professionals
alike.  It is a great opportunity to meet observers from around the globe
and learn about research and projects being carried out.  Details on
registration can be found on the IMO website at http://www.imo.net.  For
email queries, contact Eva Bojurova or Valentin Velkov at
planetarium at triada.bg

For more information on upcoming astronomy meetings, see: "International
Astronomy Meetings List" at http://cadcwww.hia.nrc.ca/meetings

5. For more info...

NAMN email:  namn at namnmeteors.org
NAMN website: http://www.namnmeteors.org

Mark Davis, meteors at comcast.net
Goose Creek, South Carolina, USA
Coordinator, North American Meteor Network

Cathy Hall, chall at cyberus.ca
Metcalfe, Ontario, Canada
Writer, NAMN Notes

Lew Gramer, dedalus at alum.mit.edu
Medford, Massachusetts, USA
Coordinator, Public Outreach
Owner/Moderator, 'MeteorObs'

Kevin Kilkenny, namnfireball at earthlink.net
Staten Island, New York, USA
Coordinator, Fireballs and Meteorites

Back issues of NAMN Notes can be found online at the NAMN website and in
the MeteorObs archives at:
http://www.meteorobs.org by selecting 'Browse Archive by Month'

To subscribe to the meteor email list:
Contact Lew Gramer at: dedalus at alum.mit.edu

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Here's to 'Clear Skies' for September...

September 2004 NAMN Notes
written by Cathy Hall & edited by Mark Davis
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