(meteorobs) NAMN Notes: November 2006
Mark Davis
meteors at comcast.net
Fri Nov 3 14:29:33 EST 2006
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NAMN Notes: November 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. Leonids - Enhanced Activity?...
2. Taurids - and Comet 2P/Encke...
3. Alpha Monocerotids...
4. Other November Meteors...
5. Upcoming Meetings...
6. For more info...
1. Leonids - Enhanced Activity?...
November means Leonids! Will we have any surprises this year?
The Leonids (LEO) reach a peak on November 17th this year at about 20h50m
Universal Time (UT) according to the detailed Leonid description in the
International Meteor Organization )IMO) 2006 Meteor Shower Calendar. Note
that November 17th is the traditional peak for the Leonids.
However, there are also predictions of enhanced activity on other dates due
to encounters with other sources of dust from the parent comet. The
duration of the shower is from November 14th to 21st.
ZHR rates this year are listed as 100+ meteors per hour. However, these
predicted rates are for November 19th, not for the traditional peak on
November 17th, which is expected to be about 10 meteors per hour. Observers
should be on alert all nights though - as the Leonids have been known to
hold surprises. The rates are predicted to be lower on the 17th - but do
you want to risk being one of the observers who missed out on some wonderful
unexpected activity that night?
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 at the zenith.
A map of the Leonid radiant can be found on the IMO website at
http://www.imo.net/calendar/2006/fall. Leonids are fast meteors, with a
velocity of about 71 km per second.
The IMO gives more specific details on what to expect this year:
"... the ending of the strong to storm Leonid returns between 1998-2002,
associated with the 1998 perihelion passage of parent comet
55P/Tempel-Tuttle, have not meant an end to interest in this fascinating
shower. This year may bring a return to still higher Leonid activity,
perhaps with ZHRs of 100-150. The timing above is for the nodal crossing,
and if recent past years are a guide, any associated activity near then may
be swamped by other filaments within the stream."
"The prediction of higher (though not storm!) rates from the 1933 filament
by Rob McNaught and David Asher is timed for November 19, 4h45m UT. More
recent work by Esko Lyytinen and Tom van Flandern gave a fractionally
different timing of 4h48m UT, which essentially confirmed the earlier
findings... A peak close to the nodal crossing time would favour sites
across Asia, but the possibly enhanced maximum timing would be best for
sites in eastern North America and all of South America eastwards to Africa
and Europe."
"Other possible maxima are not excluded... and observers should be watching
as often as conditions allow throughout the shower, in case something
unexpected happens..."
The Armagh Observatory website discusses the November 19th predictions by
David Asher and Rob McNaught at
http://www.arm.ac.uk/leonid/2006/info2006.html:
"In 2006, on November 19th, the Earth passes very close to the centre of the
trail created at the comet's 1932 return (i.e. 2 revolutions ago)... The
encounter with the 1932 trail will lead to enhanced meteor activity: a nice
outburst, but below storm level. The calculated peak time of the outburst
is 04:45 UT... It will probably not last very long (i.e. meteor activity
will rise and fall quite sharply) and so to see it you need to be in the
right part of the world..."
"McNaught and Asher... predicted the peak ZHR... for the 2006 outburst as
150... In fact an empirical correction for how much the trail diffuses
during each revolution... reduces the value of 150 to around 120... Meteors
in the outburst are expected to be quite faint... Apart from the encounter
with the 1932 Leonid trail, there is a background to the Leonid shower for
more than a week, at rather low rates (e.g. ZHR of 10 or so)."
The 2006 predictions by Mikhail Maslov of Russia include the following
activity due to encounters with old debris trails, from his website at
http://feraj.narod.ru/Radiants/Predictions/Leonids2006eng.html:
from the debris trail ZHR
formed in the year meteors/hr date / time (UT)
1932 35 Nov 19 / 4.55
1366 1 Nov 20 / 6.28
He also provides some interesting graphs, including an expected profile of
Leonid activity showing both the traditional maximum on the 17th (listed by
Maslov as 14:34 UT) and the predicted outburst from the 1932 debris trail on
the 19th (at 4:55 UT). For the traditional peak, he suggests that "its
intensity will be below normal level, with ZHR about 10-15 meteors."
Maslov comments on the visual activity predicted for the 19th, and the much
stronger telescopic and radio rates expected:
"...meteors should be very faint during the outburst. It is very possible
that average meteor brightness will decrease to 4-5 mag., so for proper
observations very good conditions with transparent and not light-polluted
sky are necessary. Duration of the outburst (period with activity above the
half of maximum level) will be about 9 hours around mentioned maximum
time..."
"Much stronger activity, up to stormy levels, is likely in radio range. It
is because the Earth will pass through the part of 1932 trail consisting of
very tiny particles, which will give very faint meteors, mostly beyond of
visual brightness range. Therefore during this outburst telescopic and
radio observations are very recommended..."
"We'd like to note a great importance of Leonid observations this year. The
obtained results can confirm or disprove the predictions. Also, the
predictions cannot consider all the finest features of stream dynamics, so
there is always a chance of unexpected activity..."
Check out Maslov's website to read the full details and the geographical
comments, and also to check out the excellent graphs and maps provided.
Esko Lyytinen emphasizes the expectation of faint meteors, in a posting to
the MeteorObs email list on March 11th of this year - but the need to always
be alert to unexpected activity:
"In principle strong showers could be possible in any year of the parent
comet orbit but are... <unlikely> many years from the comet's perihelion.
I am now (also) mainly interested on this year's two revolution trail
encounter. This is a very good encounter (considering the miss-distance)...
The 1969 shower is the only reference... Not a high ZHR is expected, but
the predicted big population index means quite a lot dim meteors. How much
does this mean for example with telescopic observations is what I don't
know, but am interested to get to know..."
It should be noted that for each Leonid return, meteor researchers check out
possible activity from many different dust trails ejected by the parent
comet in many different years, through many different centuries. This 1932
trail being discussed is but one of many dust trails.
For information on the dust trails ejected in 1899 and 1965 for instance,
check out the calculations of meteor researcher Mikiya Sato at
http://fas.kaicho.net/tenshow/meteor/55p2006/v01.htm. Sato also provides an
interesting comparison of the parameters of the 1932 dust trail and meteor
activity - as predicted this year, and as actually observed in the outburst
in 1969. He warns though, about expecting only faint meteors:
"Moreover, we must be careful predicting the meteor magnitude. In <the
article on the 1969 outburst, in Sky and Telescope> there was such
description as several meteors left trains lasting about eight seconds. As
for this thing, it suggests the possibility that the bright meteor appear in
this year, contrary to expectation..."
Lastly, there are some excellent details by Jeremie Vaubaillon at
http://www.imcce.fr/en/ephemerides/phenomenes/meteor/DATABASE/Leonids/2006
One graph gives a great overview of the whole Leonid meteoroid stream in
the vicinity of the Earth in November 2006. (As the use of the data on
Vaubaillon's site is specified as strictly regulated by the IMCCE, we cannot
list details here - but definitely check out the website to read up on
activity for dates following November 19th.)
If you want to record visual data for the meteor researchers,
check out the 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
To read any last minute comments on Leonid activity, we suggest you join our
MeteorObs discussion group. Our online subscribe form can be found at
http://www.meteorobs.org/subscribe.html. You can use this simple form to
subscribe - or unsubscribe - at any time. By signing on, you will be able
to read the discussions - and hear about the meteor observations around the
globe as they are reported. Questions from new observers are also always
welcome.
2. Taurids - and Comet 2P/Encke ...
November brings the peak of the Taurid meteor showers - part of the complex
of showers associated with Comet 2P/Encke.
The southern Taurids (STA) peak about November 5th and last until about
November 25th. Peak rates usually last for a number of days, and the ZHR
rate is about 5 meteors per hour at the maximum.
The northern Taurids (NTA) peak about November 12th and last until about
November 25th as well. Peak rates will usually last a number of days, like
the southern Taurids, and the ZHR rate is also about the same - about 5
meteors per hour around the peak.
The International Meteor Organization comments on Taurid activity
in recent years:
"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. A map showing these two
meteor shower radiants, and their movement throughout November, can be found
at http://www.imo.net/calendar/2005/fall. Their slow motion across the sky,
and the possibility of bright, fireball class magnitude meteors, make the
Taurids a particularly rewarding shower to observe.
3. Alpha Monocerotids...
The alpha Monocerotids (AMO) peak on November 21st at about 21h05m UT, but
can be seen from about November 15th to 25th. These are fast meteors, with
a velocity of about 65 km per second.
The ZHR rate for this shower is listed as variable, but is usually about 5
meteors per hour. This variable factor indicates that the shower should
always be monitored closely each year for outbursts or unusual activity.
The alpha Monocerotids may have a 10-year periodicity. Enhanced activity
was observed in 1925, 1935, and 1985. The last outburst was in 1995, and
was seen by many observers across Europe. The maximum rate in 1995 was
about 420 meteors/hour but this lasted for only about 5 minutes, with the
entire outburst duration about 30 minutes.
A map of the radiant can be found at
http://www.imo.net/calendar/2006/fall
Due to the timing this is a great opportunity to monitor both the alpha
Monocerotids - and any late enhanced Leonid activity. (If you haven't
looked at Jeremie Vaubaillon's Leonid graphs yet, go to
http://www.imcce.fr/en/ephemerides/phenomenes/meteor/DATABASE/Leonids/2006
and very carefully look at them now.)
4. Other November Meteors...
The Orionids (ORI), although reaching a peak back about October 21st, can be
observed through until about November 7th. These are fast meteors at about
66 km per second. Rates at the peak brought some surprises this year, but
rates in early November will be much lower. These meteors are always of
interest due to their parent body being the famous Halley's Comet. To see a
map of the radiant for this meteor shower, check out
http://www.imo.net/calendar/2006/fall.
The chi Orionids (XOR), although not reaching a maximum until December 2nd,
can be seen starting about November 26th. These are almost slow meteors
with a velocity of about 28 km per second. ZHR rates at the maximum will be
about 3 meteors per hour, but rates in November will be lower. A map
showing the radiant position can be found in IMO Calendar at
http://www.imo.net/calendar/2002
The December Phoenicids (PHO), although not peaking until December 6th, can
be observed starting about November 28th. This is a southern shower with
the radiant at -53 degrees, but is included for those observers in southern
latitudes. These are very slow meteors, at about 18 km per second. The ZHR
rate is listed as variable, which means observers should always monitor
the shower for unexpected activity. Back in 1956 rates did reach about 100
meteors per hour at the peak. A map of the radiant can be found at
http://www.imo.net/calendar/2004/fall
Lastly, the Monocerotids (MON) start to become active about November 27th,
although the peak will not occur until about December 9th. These are
average velocity meteors at about 42 km per second. ZHR rates at the peak
will be about 3 meteors per hour, and rates in November low. To see where
the meteors will come from, check out the map at
http://www.imo.net/calendar/2006/fall
For other November 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 November'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:
Saturn 0.5 in Leo, high in the east in the morning sky
On November 8th a transit of the planet Mercury across the Sun can be seen
(with proper solar viewing protection) from North and South America, the far
east, and Australia. As there are only about 13 of these per century, they
are fairly rare.
The phases of the moon for November are as follows:
Sun. Nov. 5 full moon
Sun. Nov. 12 last quarter
Mon. Nov. 20 new moon
Tues. Nov. 28 first quarter
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.
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 November...
November 2006 NAMN Notes
written by Cathy Hall & edited by Mark Davis
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