(meteorobs) NAMN Notes: October 2004

Mark Davis meteors at comcast.net
Tue Oct 5 20:13:40 EDT 2004


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NAMN Notes: October 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. Draconids - Debris from Comet Giacobini-Zinner...
2. Orionids...
3. Other October Showers...
4. Upcoming Meetings...
5. For more info...


1. Draconids - Debris from Comet Giacobini-Zinner...

The Draconids are an extremely interesting fall meteor shower - with both a
very interesting history and a very interesting future! It is important
for all observers to take a look at this shower - as incredible meteor
storms have happened this century for this shower.

The Draconids consist of debris from Comet Giacobini-Zinner. Sometimes the
shower is referred to as the Draconids, named after the constellation of
Draco, where the meteors seem to come from in the sky - and sometimes the
shower is referred to as the Giacobinids (GIA), after the name of the
comet.

A brief history of this comet is found in Gary Kronk's book "Comets - A
Descriptive Catalog":

"Giacobini (Nice Observatory) discovered this comet about 1 degree south of
Upsilon Aquarii on December 20, 1900 (at discovery magnitude: 10.5)
(and last observed it) on February 16 when near magnitude 15.5... the
comet was recognized as a new short-period comet... on October 23, 1913
Zinner (Bamberg, Germany) accidentally found the comet while observing
variable stars near Beta Scuti... Observations of Comet Zinner were made
for a week before identity with Comet Giacobini was first suggested and
shortly after mid-November identity was firmly established... These
calculations showed that the actual period in 1900 had been 6.46 years,
thus causing the comet to arrive at perihelion 6 months earlier than
expected at the 1913-14 return."

"Comet Giacobini-Zinner is especially noteworthy for its system of meteors,
which was first detected at its 1926 apparition. In October of that year an
unexpected shower occurred when Earth crossed the comet's orbit 70 days
before the comet. The shower... was absent until the comet next appeared in
1933. In that year Earth crossed the orbit 80 days after the comet on
October 9 and a shower of 300 to 1,000 meteors per minute was noted at one
time... in 1946, when Earth crossed the comet's orbit only 15 days after
it, a spectacular shower appeared with observed rates varying from 3,000 to
32,000 per hour."

Some photos of Comet Giacobini-Zinner can be found on Kronk's
'Cometography' website at http://cometography.com/pcomets/021p.html

Personal accounts of the 1946 Giacobinids are interesting. Several friends
of mine saw the display in 1946. Stan Mott of Ottawa, Canada was up
in North Bay, Ontario with the group led by Dr. Peter Millman. He was the
group's official recorder - manually recording all the observations! Mott
said that there were so many meteors that they just started watching
specific areas, like the head of Draco. With all the point meteors, he said
that "it looked like the eyes were just winking." When asked if there were
lots of both bright and faint meteors, he said that most seemed to be about
magnitude 2, but then added that they gave up on anything fainter than
about magnitude 3. He said that there were a mixture of long and short
meteors, and that some had trains. Most of the meteors seemed to be white
in color. He said that it "really did look like a shower," and that "the
meteors were coming fast and furious, with several at any instant." It was
cold in North Bay, and they were all bundled up in heavy blankets. In
Stan's words, they all looked like "Tibetan monks studying the stars for
omens... "

Another friend observed the display from just outside Ottawa. As a girl of
about 16 then, Mary Henderson said that she "was just totally overwhelmed
at the marvelous display." Mary went on to become a summer student of Dr.
Millman's, and in the summer of 1952 helped him analyze photographs of the
Giacobinids taken by a news photographer in Chicago.

According to the IMO, the International Meteor Organization:

"Most detected showers were in years when the stream's parent comet,
21P/Giacobini-Zinner, returned to perihelion, as last in 1998 November...
(when EZHRs briefly reached 700)... The next return of the comet is in mid
2005."

So, when does this shower happen this year, and what will we see?

The Draconids (GIA) can be seen from about October 6th to 10th. There are
several time periods that may have higher rates, although observers should
monitor as many of the nights as possible:

Fri. Oct. 8, 2h 10m UT
ie. Thurs. Oct. 7 at 10.10 p.m. EDT (Thursday night),
corresponds to 1998 outburst time

Fri. Oct. 8, 10h UT
ie. Fri. Oct. 8 at 6.00 a.m. EDT (Friday pre-dawn),
main expected time this year

Fri. Oct. 8, 15h 40m - 18h 50m UT
ie. Fri. Oct. 8 at 11.40 a.m. - 2.50 p.m. EDT
(daytime in N.America), corresponds to 1999 minor outburst time

These meteors are extremely slow, with a velocity of about 20 km per
second, so will be very easy to differentiate from other meteors. The
radiant at maximum will be at 262 degrees, ie. RA 17h 28.2m, Dec +54,
which is just north of the star beta Draconis, the star known as
Restaban, in the head of Draco. A map showing the radiant can be
found on the website of the IMO, the International Meteor
Organization, at
http://www.imo.net/calendar/cal04.html#Draconids

ZHR rates are variable, and periodic, for this shower, sometimes reaching
storm levels. What is ZHR? It 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.

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.

Due to the slow velocity of these meteors, photography and imaging of this
meteor shower are also suggested. We welcome your observations - and
recommend that all observers make every attempt to get out and see if this
shower gives us any marvelous surprises this year!


2. Orionids...

The Orionids (ORI) reach a maximum on October 21st this year, with a
radiant at 95 degrees, ie. RA 6h 19.8m, Dec +16, which is located by
following a line from the right star of the belt of Orion up through
Betelgeuse, the left shoulder star, and continuing on for about the same
distance again. A map showing the movement of the radiant from October 2nd
through to November 7th can be found at
http://www.imo.net/calendar/cal04.html#Orionids

This well-known shower is debris from Halley's Comet. This comet can be
traced back to the year 240 B.C. The closest approach of the comet to earth
was in the year 837, when we were separated from the comet by only 3.2
million miles, .0342 AU, Astronomical Units. The tail reached about 60
degrees across the sky. The recent appearance of Halley's Comet in the
1980's produced a tail of only about 15 degrees in length, and a maximum
brightness of about 2.6, fainter than the stars in the Big Dipper. Halley
is not one of the brightest comets of our time - but it is definitely one
of the most publicized. Some photos of Halley's Comet can be found on
Kronk's website as well, at http://cometography.com/pcomets/001p.html

ZHR rates for the Orionid meteor shower are about 23 meteors per hour. It
is a nice, dependable shower, and an enjoyable one to observe for the whole
month of October. These are fast meteors, with a velocity of about 66 km
per second.

According to the IMO, the International Meteor Organization:

"the Orionids were always noted for having several lesser maxima other than
the main one... helping activity sometimes to remain roughly constant for
several consecutive nights centred on this peak. In 1993 and 1998, a
submaximum about as strong as the normal peak was detected on October 17/18
from Europe, for instance. All observers should be aware of these
possibilities..."


3. Other October Showers...

The delta Aurigids (DAU), although having reached a peak back on September
9th, can be observed through until about October 10th. These are fast
meteors at about 64 km per second. ZHR rates back around the peak were
about 5 meteors per hour, but rates in October will be very low. A map
showing the location of the radiant can be found at
http://www.imo.net/calendar/cal04.html#delta-Aurigids

The epsilon Geminids (EGE) reach a maximum on October 18th, and can be seen
from about the 14th to 27th. On the 18th, the radiant will be at 102
degrees, ie. RA 6h 48m, Dec +27, which is several degrees north of the star
epsilon Gemini, also known as Mebsuta. A map showing the location of the
radiant can be found at http://www.imo.net/calendar/cal04.html#Orionids.
These are also fast meteors with a velocity of about 70 km per second. ZHR
rates at the peak will be about 2 meteors per hour.

The northern Taurids (NTA) and southern Taurids (STA) start to become
active about October 1st, but do not peak until early November. Both
showers have slow meteors, with the northern Taurid velocity at 29 km
per second and the southern at 27 km per second. At maximum in November,
both showers will have ZHR rates of about 5 meteors per hour, but rates in
October will be low. These meteors are part of the Taurid stream which has
been associated with Comet Encke. For a map showing the movement of the
radiants throughout the month, check out
http://www.imo.net/calendar/cal04.html#Taurids. The Taurids should be
monitored carefully. According to the IMO "the next potential
October-November 'swarm' (ie. fireballs) is not predicted until
2005, but we cannot be sure how correct this is as yet..."

Besides October'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    -4.1   very bright in east in morning sky
Jupiter  -1.7   very low in east in morning sky
Saturn    0.2   in Gemini

On Tuesday Oct. 12, Jupiter will be 1.6 degrees south of the moon. On
Thurs. Oct. 28, there will be a total lunar eclipse for the 'Hunter's
Moon' - completely visible from most of the America's and western Europe,
and partly visible from the rest of Europe and western Asia. For a map
of your sky with the moon and all 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:
Wed.   Oct. 6 last quarter
Thurs. Oct. 14 new moon
Wed.   Oct. 20 first quarter
Thurs. Oct. 28 full moon
For a great printout of moon phases for the month, check out
http://stardate.org/nightsky/moon


4. Upcoming Meetings...

For 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 October...

October 2004 NAMN Notes
written by Cathy Hall & edited by Mark Davis
==============================================




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