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
1. Leonids - Enhanced Activity?...
2. Taurids - and Comet 2P/Encke...
3. Alpha Monocerotids...
4. Other November Meteors...
5. Upcoming Meetings...
6. For more info...
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...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. Inthere 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 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@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.
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.
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.)
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@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 quarterA wonderful monthly moon calendar can be printed off from http://stardate.org/nightsky/moon. For the NASA kids' calendar for August, 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.
For information on upcoming astronomy meetings, see: "International Astronomy Meetings List" at http://cadcwww.hia.nrc.ca/meetings
NAMN email: namn@namnmeteors.org
NAMN website: http://www.namnmeteors.org
Mark Davis, meteors@comcast.net
Goose Creek, South Carolina, USA
Coordinator, North American Meteor Network
Cathy Hall, chall@cyberus.ca
Ottawa, Ontario, Canada
Writer, NAMN Notes
Lew Gramer, dedalus@alum.mit.edu
Homestead, Florida, USA
Coordinator, Public Outreach
Owner/Moderator, 'MeteorObs'
Kevin Kilkenny,
namnfireball@earthlink.net
Staten Island, New York, USA
Coordinator, Fireballs and Meteorites
Back issues of NAMN Notes can be found on-line at the NAMN website
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http://www.meteorobs.org
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to find out information on our weekly chat sessions:
Contact Lew Gramer at:
dedalus@alum.mit.edu