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. Draconids - Any Surprises This Year?...
2. Orionids - Debris from Halley's Comet...
3. Watch for Taurid Fireballs...
4. Other October Activity...
5. Upcoming Meetings...
6. For more info...
The Draconids, or Giacobinids (GIA) as they are sometimes called, peak on October 8th this year at about 16h Universal Time (UT). All observers should be alert for surprises over the full course of the shower, from October 6th to 10th.
The ZHR for this meteor shower is listed as 'variable' by the International Meteor Organization (IMO). 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 AU (Astronomical Units) in distance from the earth. The comet reached magnitude 6, and a meteor storm was encountered. The most recent return was in 1998. 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. The comet returns to perihelion again in July this year, but whether it will have any effect on the Draconids we see in 2005 is not clear..."
"The 1998 outburst happened at... <the equivalent of> 2005 October 8, 8h15m UT... In 1999 an unexpected minor visual-radio outburst (ZHRs ~ 10-20) occurred over the Far East... A repeat at this time would fall between 2005 October 8, 21h40m to October 9, 0h50m UT."
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 the IMO 2005 Meteor Shower Calendar at http://www.imo.net/calendar/2005/fall
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. If you have any questions, drop a note to our NAMN Coordinator at meteors@comcast.net
NAMN has some good star charts to mark your radiants on before you go out observing. These charts also show constellations for the whole sky, and give the brightness of a number of stars to use in judging the magnitude of the meteors you see. Our 4 printable charts can be found at 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
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.
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 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.
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 area of the sky where the meteors from Halley's Comet seem to come from can be seen on the map at http://www.imo.net/calendar/2004/fall. Get out and enjoy this wonderful fall shower!
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.
However, these meteor showers are part of the complex of showers associated with Comet 2P/Encke - and could provide some surprises this year. The IMO refers to 2005 being a 'potential Taurid Complex meteoroid "swarm" return year'. In their 2005 Meteor Shower Calendar they comment further:
"David Asher has indicated that increased Taurid fireball rates may result from a 'swarm' of larger particles within the Taurid stream complex, and he suggested such "swarm" returns might happen in 1995 and 1998 most recently. 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. This year brings the next potential October-November "swarm" return. Thus, observing what happens with the Taurids between last quarter Moon in October through to the Northern Taurid maximum in November is most important..."
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 the radiant movement over the next 2 months can be found at http://www.imo.net/calendar/2005/fall#taurids
All observations are encouraged - not just for the supposed peak times in November - but all throughout the months of October and November as well. It is those observers who will be rewarded with surprises from the Taurids...
The delta Aurigids (DAU), although having peaked back in September, can still be observed 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 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/2004/fall
For other minor showers not on the International Meteor Organization's, 'Working List of Visual Meteor Showers', check out the very informative website 'Comets and Meteor Showers' by Gary Kronk at http://comets.amsmeteors.org. It gives further details on more obscure showers, and a wealth of observational and historical detail on all the major and minor showers.
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.
Planets at midmonth, and their magnitudes, for northern observers, are:
Venus -4.1 low in southwest in evening twilight Mars -1.9 in Aries (brightening, closest to earth on October 30) Saturn 0.4 in Cancer, in east in morning sky
For a sky chart showing the positions of all the planets visible this month, go to http://www.heavens-above.com, select your country, then your city, and go to 'Whole Sky Chart'.
The phases of the moon for October are as follows:
Mon. Oct. 3 new moon Mon. Oct. 10 first quarter Mon. Oct. 17 full moon, the 'Hunter's Moon' Tues. Oct. 25 last quarter
For a great printout of moon phases for the month, check out http://stardate.org/nightsky/moon. There is a partial lunar eclipse on October 17th, visible from central and western North America, parts of Central America, most of Asia, and Australia.
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
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