(meteorobs) NAMN Notes: November 2008

[meteors at comcast.net]

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NAMN Notes: November 2008
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NAMN Notes is a monthly newsletter produced by the North American Meteor
Network It 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...


1. Have the Leonids Returned to Being a Minor Shower?...

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)


2. Autumn’s Showers Wind Up and Down...

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.html

STA - 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)


3. Don’t Blink or You Might Miss an AMO Outburst...

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)


4. The Andromedids Live...

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)


5. Winter’s Showers Start Earlier Than Expected...

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


6. Sky References...

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.


7.  For More Information...

For radiant positions and more detailed descriptions of showers, see the
IMO 2008 Meteor Shower Calendar at:  http://www.imo.net/calendar/2008

For 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.html

It’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 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

Wayne T Hally, meteoreye at comcast.net
High Bridge NJ
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 2008 NAMN Notes
Written by Wayne T. Hally & edited by Mark Davis
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