(meteorobs) NAMN notes

Tue Oct 10 12:49:36 EDT 2006

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NAMN Notes:  October 2006
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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.  October - Monitor the Draconids...
2.  Orionids and Halley's Comet...
3.  Taurids and Fireballs...
4.  Other October Activity...
5.  Upcoming Meetings...
6.  For more info...

1.  October - Monitor the Draconids...

October brings Draconids - or Giacobinids (GIA) as they are sometimes
called.  The name Draconids comes from the constellation of Draco, where the
meteors seem to come from in the sky.  The name Giacobinids comes from the
name of the parent comet from which the meteors originate.

These meteors peak about October 8th, but the strength of the shower is
difficult to predict.  According to the IMO, the International Meteor
Organization:

"Potential Draconid hunting will be entirely impractical this year, unless
there is a strong outburst (none are predicted), thanks to full Moon on
October 7.  If anything were to occur from them, their possible past peak
timings would span October 8, 14h30m UT (... the equivalent 1998 outburst
time) and 22h20m UT (the nodal crossing time...), to October 9, 4h - 7h UT
(the equivalent 1999 minor outburst time...)."

UT stands for Universal Time, and is the time in Greenwich, England.  For
observers in eastern North America, these times correspond to (subtracting 4
hours) a span of from Sunday October 8th 10.30 am EDT to 6.20 pm EDT to
midnight EDT to Monday October 9th at 3.00 am EDT.

The shower runs from about October 6th to 10th - and observers should be
alert for surprises over the full course of the shower.

The ZHR for this meteor shower is listed as variable by the
International Meteor Organization. What is ZHR? This is Zenithal Hourly
Rate, and is the number of meteors that an observer would expect to see, on
average, in an hour, if they are out observing under dark country skies,
and if the radiant, the area in the sky where the meteors seem to come from,
is directly overhead.

The parent comet of the Draconids is Comet Giacobini-Zinner.  It was
discovered by Michel Giacobini of France in 1900, and also by Ernst Zinner
of Germany in 1913.  The comet is a short period comet, returning about
every 6 1/2 years.  The 1946 return was notable as the comet passed only
0.26 Astronomical Units (AU) in distance from the earth.  The comet reached
magnitude 6, and a meteor storm was encountered.  Some photos of Comet
Giacobini-Zinner can be found on Gary Kronk's 'Cometography' website at
http://cometography.com/pcomets/021p.html

The first prediction for a meteor shower from this comet was made in 1915 by
Reverend M. Davidson.  Meteors from the predicted radiant were observed by
William Denning.  In 1933 a wonderful storm was seen - with observers
reporting meteors falling like snowflakes with rates of about 100 meteors
per minute (6000 per hour) depending on observer and location.  The meteors
were described as faint, with most being between magnitude 3 and 5.  They
were slow, and most were yellow in color.  In 1946, Czechoslovakian
observers saw a corrected rate of about 6800 meteors per hour.  That year
was the first time a meteor shower was detected also by radar.

According to the IMO:

"The Draconids are primarily a periodic shower which produced spectacular,
brief, meteor storms twice last century, in 1933 and 1946, and lower rates
in several other years (ZHRs ~ 20-500+), most recently in 1998 (when EZHRs
briefly reached 700).  Most detected showers were in years when the stream's
parent comet, 21P/Giacobini-Zinner, returned to perihelion, as it did in
1998 November...  In 1999 an unexpected minor visual-radio outburst (ZHRs ~
10-20) occurred over the Far East..."

Regarding the Draconids in 2005, the IMO Shower Circular comments on the
shower activity observed last year:

"An outburst of Draconid activity was observed from Asian and eastern
European geographical longitudes on October 8, 2005.  The activity was also
observed by radar technique...  With a population index of r = 3.0, an
equivalent ZHR near 150 was derived (Campbell-Brown et al., Univ. of Western
Ontario).  Visual rates may be lower due to the different range of larger
masses causing visual meteors... 08 16:10 ZHR 34.3..."

On the MeteorObs email list, Russian researcher Mikhail Maslov commented in
May 2006 on what we might expect to see this year:

"Draconids 2006... Analysis of non-perihelion particles says that in 2006
Draconids can give a radio outburst with maximum at 09.10.2006 4:43 UT.
Ejection velocity 86.7 m/s and the bright moonlight leaves no chances for
significant visual activity."

In spite of the moonlight, visual observations are still needed!  This
shower <can> hold surprises.  Observe - but block the moon from your view as
much as possible.  Put it behind a tree, or block it with your car, or face
the other direction in the sky.

The Draconids are very distinctive, slow moving meteors, at about 20 km per
second, and that characteristic will help make them easier to differentiate
from any random sporadic meteors.

The radiant for the Draconids, at the peak, is at 262 degrees, ie. RA 17h
28.2m, Dec +54, which is just north of the star beta Draconis also known as
Restaban, in the head of Draco.  A map showing the radiant can be found in
last year's IMO Meteor Shower Calendar at
http://www.imo.net/calendar/2005/fall

If you want to record visual data 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.  If you have any questions, drop a note to the NAMN Coordinator at
meteors at comcast.net

For visual observers, NAMN has a set of 4 star charts to help you judge the
brightness (magnitude) of the meteors you see.  They are also a great tool
for new observers to help you learn your constellations better.  The charts
can be printed off from http://www.namnmeteors.org/charts.html.  Set your
printer to landscape mode.

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

2.  Orionids and Halley's Comet...

The Orionids (ORI) peak on October 21st this year, and can be observed from
about October 2nd through to November 7th.  These are fast meteors, at about
66 km per second.  ZHR rates are about 23 meteors per hour.

The area of the sky where the meteors seem to come from can be seen on the
map at http://www.imo.net/calendar/2006/fall

According to the IMO:

"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..."

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 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 Gary
Kronk's website at http://cometography.com/pcomets/001p.html

Both Halley and his comet make interesting reading.  Edmond Halley was born
in Haggerston, England in 1656, and died in Greenwich, England in 1742.  His
accomplishments were quite varied.  He improved the sextant.  He sailed to
the southern hemisphere and collected data on the ocean and atmosphere - and
published the first meteorological chart in the world.  He catalogued 341
southern hemisphere stars, and discovered a star cluster in Centaurus.  He
made the first complete observation of a transit of Mercury.  Halley urged
Newton to publish his 'Principia Mathematica', and paid for the costs out of
his own pocket.  While sailing the Atlantic Ocean in command of a warship,
courtesy of King William III, Halley made studies of longitude and tides.

It is wonderful to think as we observe these meteors that we are seeing
pieces of debris from the famous Halley's Comet.  But wait - did Halley
really discover this comet?  Surprisingly, no.

In the realm of comets, Halley believed that elliptical orbits might exist.
He believed that the comets of 1531, 1607 and 1682 were all the same
comet - a periodic comet - and predicted that it would return again in 1758.
When the prediction came true, after Halley's death, the periodic comet was
renamed in his honor.

The discovery of the Orionid meteors themselves is generally credited to
Edward Herrick in 1839.  Precise observations of the radiant were first made
in 1864 by Alexander Herschel.  The first measurements of meteor rates for
the shower were done in 1892.  The link between the shower and the comet
came indirectly.  It had been known since 1868 that the Eta Aquarid meteor
shower in May was related to Halley's Comet.  In 1911, Charles Olivier
mentioned the similarity of the orbit of the Orionids to that of the Eta
Aquarids - and hence the first linkage in turn was made to Halley's Comet,
although it was not generally accepted until a number of years later.

The Orionids are a great fall shower - lots of meteors and longer nights -
brought to you courtesy of Halley, Herrick and Herschel!

3.  Taurids and Fireballs...

The southern Taurids (STA) and the northern Taurids (NTA) both start to
become visible about October 1st - and both showers last through until about
November 25th.  They will not peak until November, the southern on November
5th and the northern on November 12th, but activity is visible over a long
period, and the peak rates actually last for a number of days.  The normal
ZHR rate is about 5 meteors per hour at the peak.

These meteor showers are part of the complex of showers associated
with Comet 2P/Encke.

The IMO states that late October is a 'potentially interesting' time for the
Taurids:

"In 1995, an impressive crop of bright Taurids occurred between late October
to mid November, while in 1998, Taurid ZHRs reached levels comparable to the
usual maximum rates in late October, together with an increased flux of
brighter Taurids generally..."

Both showers have almost slow meteors - the southern at about 27 km per
second and the northern at about 29 km per second.  Their slow motion
across the sky, and the possibility of bright, 'fireball' class magnitude
meteors, make the Taurids a particularly rewarding shower to observe.

A map showing these two meteor shower radiants, and the radiant movement
over the next 2 months, can be found at
http://www.imo.net/calendar/2005/fall#taurids

4.  Other October Activity...

The delta Aurigids (DAU), although having peaked back in September, can
still be observed through until about October 10th.  These are fast meteors
at about 64 km per second.  Although ZHR rates were about 5 meteors per hour
around the peak, rates in October will be lower.  A map of the radiant can
be found at http://www.imo.net/calendar/2005/summer#delta-aurigids.

The Sextantids, a daytime meteor shower normally detected by radio
observers, could yield some visual meteors.  The radiant is at 152 degrees,
ie. RA 10h 7.8m, Dec +0.  Although the peak is listed as late September, the
shower runs through until about October 9th.

The epsilon Geminids (EGE) reach a maximum on October 18th, and can be seen
from about October 14th to 27th.  These are fast meteors at about 70 km per
second.  ZHR rates at the peak are about 2 meteors per hour.  A map of the
radiant is at http://www.imo.net/calendar/2006/fall.  These meteors can
easily be confused with Orionid meteors, so be careful with your meteor
shower associations.  Plotting is recommended.

For other October minor showers not on the International Meteor
Organization, 'Working List of Visual Meteor Showers', and for a wealth of
historical information on all showers, check out Gary Kronk's 'Comets and
Meteor Showers' website at http://comets.amsmeteors.org

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

For those of you interested in plotting your meteors (recommended for
serious observations), special IMO plotting maps can be ordered through
Robert Lunsford of the International Meteor Organization.  For details,
contact him directly at lunro.imo.usa at cox.net

To read up further on telescopic, photographic and video recording of
meteors, check out the IMO website at http://www.imo.net

Planets at midmonth, and their magnitudes, for northern observers, are:
Venus      -3.8 very low in east-northeast in morning twilight
Jupiter    -1.8 in Libra, very low in west-southwest in evening twilight
Mercury    -0.1 very low in west-southwest in evening twilight
Saturn      0.5 in Leo, high in the east in the morning sky

The phases of the moon for October are as follows:
Sat. Oct.  7  full moon
Sat. Oct. 14  last quarter
Sun. Oct. 22  new moon
Sun. Oct. 29  first quarter
On Thursday October 19, the asteroid Juno will be 0.3 degrees north of the
moon, with an occultation visible from Hawaii and southern South America.
For the rest of us, it's just close!
A wonderful monthly moon calendar can be printed off from
http://stardate.org/nightsky/moon.  For the NASA kids' calendar for the
month, go to http://spaceplace.nasa.gov/en/kids/calendar.shtml

One of the simplest sky charts can be found on the website 'Heavens Above',
at http://www.heavens-above.com.  Ignore the 'Register' bit.  Just 'Select'
your country, then your city, and then scroll down the page to 'Whole Sky
Chart'.  Type in what day you want, and pick a time of night.  Pick black on
white, as it's easier to read.  The maps show the constellations and the
positions of all the visible planets.  'Heavens Above' also tells you when
to watch for satellites, and the ISS, the International Space Station,
passing over your home or observing site.

5.  Upcoming Meetings...

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

6.  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
Ottawa, Ontario, Canada
Writer, NAMN Notes

Lew Gramer, dedalus at alum.mit.edu
Homestead, Florida, 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 2006 NAMN Notes
written by Cathy Hall & edited by Mark Davis
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