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
Headlines:
* No major showers, not even the Leonids
* Autumn’s showers continue, while winter’s start earlier than expected.
* A few minor showers, including an always possible outburst and an old
friend.
1. Have the Leonids Returned to Being a Minor Shower?...
2. Autumn’s Showers Wind Up and Down...
3. Don’t Blink or You Might Miss an AMO Outburst...
4. The Andromedids Live...
5. Winter’s Showers Start Earlier Than Expected...
6. Sky References...
7. For More Information...
2009 may give us one more year of above normal activity from the Leonids before the shower returns to the average rate of 10-15 per hour typical of the years between perihelia of comet 55P/Temple-Tuttle. In fact there may be some periods of enhancement this season, but none can be seen from North America and the moon will be an overwhelming presence. It is a grim outlook for the Leonids in 2008.
The nodal crossing, which is the time of the traditional peak, occurs during the early morning hours of the 17th. However, the 78% illuminated moon rises before the radiant and by the 19th will practically be on top of it. Jeremie Vaubaillon and Mikhail Maslov have predicted possible increased activity from old trails, but for North America, both occur before the radiant has cleared the horizon for the east coast, while it is still daylight for the west coast. At least for eastern Europe and Asia the radiant will be up, though the moon will be just as much of a hindrance there. Perhaps their best chance would be to see a 16 revolution old trail (hence brighter meteors) at about 0 UT on the 17th.
For North America, the best chance to see some Leonids may be during the early morning moon free hours at the start of activity before the Full Moon. Sirko Molau’s 2008 analysis of IMO video meteors indicated the earliest Leonids begin to show up as soon as November 6th when the morning hours will be dark, and at least one moon free hour should be possible before twilight until the morning of the 10th. There might only be one or two per hour though, so great care must be used in correctly identifying any potential shower members. Since the radiant does not rise until about 10:30 PM local time, the early morning hours are the best time to look in any case. Here are the radiant positions for selected dates (Right Ascension is given in degrees and hours and minutes, Declination in degrees).
LEO - Leonids: Velocity 71 km/sec (extremely fast) Nov 6 RA 147 (9:48), Dec +26 (start date indicated from video data) Nov 10 RA 147 (9:48), Dec +24 (IMO visual start, moon free hour in early morning). Nov 17 RA 151 (10:05), Dec +22 (peak morning) Nov 23 RA 155 (10:19), Dec +20 (IMO visual end) Nov 28 RA 160 (10:41), Dec +18 (end based on video data)
The Taurids and Orionids continue into November. The Southern Taurids peak first in late October or early November, then the northern branch reaches its maximum in the middle of the month (coincident with the full moon this year). It has been suggested that this might be another swarm year with higher rates and more fireballs, particularly in the beginning of November from the southern branch. The Taurids are rather slow moving with speeds typical for the Antihelion meteors, particularly when compared to the swift Leonids and Orionids. Based on video data, both branches continue separately at least through the end of the month so I will list positions until then. If you do not keep track of Northern and Southern Taurids, meteors after the 25th should be reported as Antihelion. Remember, that like the Antihelions, these radiants are about 20 degrees wide along the ecliptic, and about 10 degrees “tall” from north to south. Therefore some overlap occurs between them since the two are only 6 or 7 degrees apart. This is a good time to use an alignment cord to give you the best chance of determining whether a specific meteor belongs to one branch or the other. For a description of such a device, see the November 2007 NAMN Notes here:
http://www.namnmeteors.org/namnnotes0711.htmlSTA - Southern Taurids: velocity 27 km/sec (medium slow) Nov 1 RA 049 (3:15), Dec +14 Nov 5 RA 052 (3:28), Dec +15 (traditional peak) Nov 10 RA 056 (3:44), Dec +15 (last morning with a moon free hour) Nov 16 RA 061 (4:03), Dec +16 (first evening with a moon free hour) Nov 21 RA 066 (4:22), Dec +16 Nov 25 RA 072 (4:48), Dec +17 Nov 30 RA 074 (4:58), Dec +19 NTA - Northern Taurids: velocity 29 km/sec (medium slow) Nov 1 RA 049 (3:15), Dec +20 Nov 5 RA 052 (3:28), Dec +21 Nov 10 RA 056 (3:44), Dec +22 (last morning with a moon free hour) Nov 16 RA 063 (4:10), Dec +23 (first evening with a moon free hour) Nov 21 RA 066 (4:24), Dec +24 Nov 25 RA 070 (4:40), Dec +24 Nov 30 RA 075 (4:58), Dec +25
The Orionids are finishing up in November. While the IMO Working List shows an end date of October 7th, video data shows low levels of activity continuing until after the Full Moon, so I will list those positions as well. Again, since only one or two an hour is likely after the 15th, extreme care (such as an alignment cord) should be used to ensure your shower association is accurate. Be aware that the Orionid radiant is in Gemini the whole month, beginning near Alhena (gamma Gem, the 2nd magnitude star at the southwestern corner of the constellation) and ending below Castor and Pollux by the 30th.
ORI - Orionids: velocity 66 km/sec (very fast) Nov 1 RA 102 (6:49), Dec +16 Nov 5 RA 105 (7:00), Dec +17 Nov 10 RA 110 (7:16), Dec +20 (last morning with a moon free hour) Nov 16 RA 114 (7:35), Dec +21 (first evening with a moon free hour) Nov 22 RA 118 (7:52), Dec +22 (end of video activity)
The alpha Monocerotids (AMO) are usually a minor shower, but can give us some brief surprises. It has produced very short (and I do mean very!) outbursts a few times in the last century. The most recent was in 1995, with a 5 minute EZHR of 420, or about 35 meteors in 5 minutes. The pattern of outbursts has not been established, so we need to monitor this shower around the time of the expected peak, which occurs this year at 9:25 UT on November 21st. This time would make such an event visible across the continent, near morning twilight in the east. Of course, that time could be off by a few hours, so one should be alert all night. And try and limit your breaks. As the IMO says: “The brevity of all past outbursts means breaks under clear skies should be kept to an absolute minimum near the predicted peak.” I’d suggest that even blinking should be discouraged, but that may be going too far!
The radiant is technically in the constellation Canis Minor, about the same distance below Procyon as the 3rd magnitude star is above it. Certainly, if an outburst should occur, it won’t be hard to find. It might be one of the most impressive 5 minutes in a meteor career.
AMO - alpha Monocerotids: velocity 65 km/sec (very fast) Nov 16 RA 113 (7:31), Dec +02 (start of activity) Nov 21 RA 118 (7:48), Dec +01 (peak, possible outburst) Nov 25 RA 120 (8:00), Dec +00 (end of activity)
Comet 3D/Biela broke in two in 1842, and was observed as two separate comets in 1846 and 1852. After that, it was never seen again. Instead, in 1872 and 1885 the earth intercepted the debris from the shattered comet producing huge meteor storms. Today, the bulk of the stream lies far from earth’s orbit, but IMO video data shows some small activity from this shower in early November until the 18th. The meteors would be quite distinctive since the impact speed is less that 20 km/sec, one of the slowest of any shower. The radiant, which is now located very near M33 on the Pisces/Triangulum border, rises very early, so it’s a good target for the days just after the Full Moon when there only a few moon free hours after sunset. It certainly is worth taking a look. The IAU also lists this shower with a slightly displaced radiant and a peak near the Full Moon, but I will use the positions from the IMO video as it is the most current.
As an interesting personal note, there used to be in New Jersey a luxury train line called “The Blue Comet” that ran between New York City and Atlantic City from 1929 to 1941. The cars on the train were named after comets. One of the surviving observation cars, named Biela is now part of a local diner, Clinton Station, that is home to one of the largest (obscenely so) burgers in the world, the 50 pound “Zeus”. It’s only about 4 miles from the NJAA Observatory, and when the wind is blowing the right way...
AND - Andromedids: velocity 18 km/sec Nov 1 RA 023 (1:31), Dec +28 Nov 4 RA 023 (1:32), Dec +30 (IMO video indicated peak) Nov 10 RA 024 (1:35), Dec +35 (last morning with a moon free hour) Nov 16 RA 024 (1:37), Dec +40 (first evening with a moon free hour) Nov 22 RA 029 (1:57), Dec +35 (end of IAU activity)
Three of December’s showers - the Monocerotids (MON), sigma Hydrids (HYD), and Geminids (GEM) have shown up in video data before the end of November. Here I will show the start of activity, and position at the end of the month should you wish to look for any as we approach the Nov 27th Full Moon. Only the Monocerotids are listed in the IMO Working List as starting this month. They all will all be covered in more detail in the December issue, these are just targets for the experienced and interested observer willing to brave the late autumn cold for the possible very low rates. Once again, plotting, or the use of an alignment cord is suggested for accurate shower association.
MON - Monocerotids: velocity 42 km/sec (medium)
[The radiant on the peak night, based on the video results, is almost
exactly where the Orionid radiant is on its peak night. The IMO Working
List position is about 10 degrees away and it peaks in early December.
I’ll cover that in more detail next month. The peak ZHR is only two, so
these would be expected to be very rare meteors.]
Nov 17 RA 081 (5:24), Dec +14 (start of video indicated activity) Nov 22 RA 085 (5:42), Dec +15 Nov 28 RA 091 (6:03), Dec +16 (video indicated peak of activity)
HYD - sigma Hydrids: velocity 59 km/sec (fast)
[This month the radiant is located just a bit to the east of Procyon.
It peaks in mid December with a ZHR of only 3, the IMO Working List
start date is Dec 3.]
Nov 22 RA 113(7:30), Dec +06 (start of video indicated activity) Nov 30 RA 119(7:56), Dec +05
GEM - Geminids: velocity 35 km/sec (medium)
[The IMO Working List start date is December 7th, so rates, if any, this
month would be quite low. The radiant this month is halfway between
Gemini and Auriga.]
Nov 23 RA 091 (6:03), Dec +34 (start of video indicated activity) Nov 30 RA 098 (6:34), Dec +33
This month’s Full Moon is just after 0600 UT on Nov 13th, so the first half of the month will feature decreasing amounts of moon free hours in the morning. The November New Moon is during the day of the 27th, so by the end of the month almost the entire night (quite long in the northern hemisphere) should be moon free. More hours than most of us can handle! So watch the weather and pick the best time when clear skies and your life permit an observing window. As you can see, there are lots of interesting targets if you can squeeze in as much time as possible. Since the weather often gets ugly in the early winter across the whole hemisphere, you never can tell when you might be the only person on the planet watching the sky at that moment!
We have lots of bright stars to compare possible Taurid fireballs to, led of course by Sirius a piercing -1.5. Capella is nearly overhead, and Betelgeuse and Rigel also are close to magnitude zero. Procyon is only a bit dimmer at +0.5. First magnitude stars include Aldebaran in Taurus, as well as Pollux, in Gemini below the slightly dimmer (~ +1.5) Castor which is about the same as Regulus in Leo. In the early morning, Saturn also sits below the Lion at nearly 1st magnitude.
Many 2nd magnitude stars populate the sky from Alpheratz, the brightest star in the Great Square of Pegasus to Alhena in Gemini as discussed above.
3rd Magnitude stars include epsilon Gem, the “pointy” end of LM area 4, and Epsilon Leonis, the brightest star at the top of the reverse “?” that envelops the Leonid radiant.
Two stars just a tenth of a magnitude or so dimmer than 4th are those two that are near Castor and Pollux just outside of LM area 4 (neither of which should be included in the counts), while sigma Ori, the star below the left end of Orion’s belt is +3.8. Another is the star at the center of Cancer, right next to the Beehive Cluster Magnitude +3.9.
It’s hard to find 5th magnitude stars that are easy to describe in words. The best I can find this month can be found this way. To the east of Regulus (the brightest star on the eastern edge of Leo is a Magnitude +3.5 star (omicron Leonis). A little above and to the right of that is the 5th Magnitude xi Leonis.
For radiant positions and more detailed descriptions of showers, see the IMO 2008 Meteor Shower Calendar at:
http://www.imo.net/calendar/2008For assistance in understanding how to estimate limiting magnitude (the faintest stars you can see) the NAMN has a tool available here:
http://www.namnmeteors.org/lm_calc.htmlIt’s especially helpful for those new to the process.
For those who wish to look for other minor showers not listed here, or want daily radiant positions for all the showers, drop me an e-mail at my meteoreye address below, and I’ll send you my current Excel spreadsheet.
Feel free to contact us for questions and comments!!
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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
Wayne T Hally, meteoreye@comcast.net
High Bridge, NJ
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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