(meteorobs) NAMN Notes: October 2008

Tue Oct 14 21:20:39 EDT 2008

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NAMN Notes: October 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

Contents: Mostly Minor Showers, but good rates...

1. ORI - Halley’s Comet Dust Returns Again...
2. Will the Draconids (GIA) Roar?...
3. STA & NTA - New Taurid Data...
4. Minor Showers EGE and LMI...
5. DAU - Leftover Aurigids...
6. Sky References...
7. For More Information...

1. ORI - Halley’s Comet Dust Returns Again...

The major Orionid meteor shower will be a challenge in 2008 considering
the position and timing of the first quarter moon. However, during the
last two years activity has been 2 to 3 times normal and modeling has
indicated such enhanced rates may continue for another few years. So
despite the moon, we should make an effort to monitor it.

The Orionids are one of two annual showers created by Halley’s comet.
The eta-Aquarids in May occur when the Earth impacts outbound particles,
while the Orionids sample the incoming particles of the same stream. The
Orionids approach the solar system from below and are visible after
about 10 PM. However, a useful radiant elevation for scientific data
does not occur until after midnight. Unfortunately, this year the 65%
illuminated moon rises only about an hour later than the radiant on the
peak morning of the 21st, and is only 15 degrees away. As I said, it’s a
challenge. The best advice I can give is to try and keep the moon behind
a building or umbrella, and place your field of view to the west in
southwestern Taurus, or even Cetus. The radiant is about halfway between
Betelgeuse and the feet of Gemini, well above the main rectangle of
Orion’s 4 corner stars. The moon will rise a little later the next
morning (Oct 22), so there will be a bit more dark sky time, and more
distance between Luna and the radiant. That also means that the nights
before the peak will be even worse. On the morning of the 20th (night of
the 19th) the 75% full moon will rise before the radiant. If I may say
so, yuck!!

Fortunately, the Orionids are bright, so you can attempt some data
collection; however with such a bright moon in the sky, the limiting
magnitude polygons that the IMO and NAMN use will not help define the
brightness of the sky with much precision. Make an extra effort to count
the areas you use near your field of view with as much detail as you can.

Recent IMO video data has shown low but steady activity from the
Orionids as early as the beginning of September lasting until late
November! In future years this will need to be taken into account.
Outside of the IMO visual radiant period listed below I have shown the
video indicated positions. To add to the fun, a second nearby radiant
has show up that parallels the ORIs. I have listed them as XGE in the
position charts below. This extends only from the 16th (in the Full Moon
whiteout) to the 25th. While it will be difficult, there’s still plenty
to be gained by making and reporting careful observations this year.

Radiant Positions
ORI - Orionids velocity 66 km/sec (very fast)

UT Date, RA in degrees, then (Hr:mm), Declination
Oct 1   081 (5:26), +12  (IMO visual start of activity Oct 2)
Oct 6   086 (5:42), +14
Oct 12  089 (5:57), +15  (Last morning w/hour before Full Moon Whiteout)
Oct 19  093 (6:14), +16  (First evening with moon free hour)
Oct 21  095 (6:19), +16  (Orionid peak morning)
Oct 26  099 (6:34), +16
Oct 31  102 (6:47), +16

XGE - xi Geminids (a video radiant related to the Orionids)
velocity 59 km/sec (fast)

UT Date, RA in degrees, then (Hr:mm), Declination
Oct 19  108 (7:10), +11  (First evening with moon free hour)
Oct 23  104 (6:58), +11  (XGE Video Peak)
Oct 25  103 (6:51), +11  (End of activity)

2. Will the Draconids (GIA) Roar?...

The Draconid shower is a periodic shower that has produced prodigious
outbursts early in the 20th century, and a few short periods of high
rates as recently as 2005. The shower has not had sufficient data
recorded, nor modeling completed to say for sure whether it will appear
for us in any given year. Already in 2008 we have been surprised by
unexpected outbursts from the Perseids well after the normal peak, as
well as another from the separate September Perseids. So while nothing
spectacular seems likely this year, the only way to know for sure is to
watch when you can. It’s that “meteor showers are like a box o’
chocolates” thing. I would hate to hear that during a clear night I
missed a delightful shower because I didn’t look.

The Draconid shower uses the 3 letter code GIA, named for the parent
comet, 21P/Giacobini-Zinner. While this defies the usual naming
conventions, the code has been in use for so long most organizations
have continued it. The radiant is near Draco’s head, and the activity
period is usually so short no daily drift has been detected. I would
suggest watching from the morning of the 5th to the 11th, although if
anything happens this year it should be on the 7th and 8th. These are
exceptionally slow meteors, so should leave little doubt about shower
association. If the dragon’s head throws meteors at you, smile and
record them!

Since the activity period is so short, I will only list the peak night
position.

GIA - Draconids velocity 20 km/sec (very slow)

UT Date, RA in degrees, then (Hr:mm), Declination
Oct 8-9  262 (17:28), +54 (activity period Oct 6-10)

3. STA & NTA - New Taurid Data...

Once again, the voluminous video data over the last few years has helped
define the true extant of the Taurids. It has shown that the Southern
Taurids (STA) begin to show as a source distinct from that of the wide
Antihelion meteor radiant as early as the second week of September. This
might be what has been reported in the past as SET (September Taurids).
It’s too late to go back this year, but once again, future visual timing
and positions might need to be adjusted. Video data suggests the STA
shower actually peaks on October 11th, so I will list that position this
month. The IMO working list shows the peak on November 5th. While the
activity period appears much longer in the video data, the positions are
in excellent agreement.

Meanwhile, the Northern Taurids (NTA) appear to start a bit later, in
early October rather than the Sept 25 date given in the IMO shower list,
and last much longer, until mid December!! For now I will show the
official IMO shower positions during the Sept 25 to November 25th
period, as well as video indicated positions outside of that. In fact
the video data suggests two showers with a dip in between, the first
peaking October 19th, and the second November 13th, close to the working
list peak. So I will list the October information this month. Early in
October, the video and working list positions differ by more than 5
degrees, so I will have to list both.

While this is an exciting time as we gain new understanding about actual
activity, I don’t want to add too much confusion. This is a fast moving
science, and sometimes we need to ensure we are strapped in well, and
pay attention to the very latest. I hope I am helping in that effort,
rather than making things worse. For the occasional observer, follow the
IMO visual positions. Those with more experience can make the effort to
record the most detailed data you can and be clear about what radiant
positions you are using for each night’s observations.

The Taurid’s speeds are very close to that of the Antihelion meteors
which occur throughout the year, so we should all have a good feel for
the angular velocities in the sky.

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STA - S. Taurids velocity 27-29 km/sec (Antihelion speed, medium slow)

IMO Working List Positions
UT Date, RA in degrees, then (Hr:mm), Declination
Oct 1   026 (1:42). +07
Oct 7   029 (1:55), +08
Oct 11  034 (2:18), +09  (Video indicated first peak; before Full Moon)
Oct 19  039 (2:37), +12  (First evening with moon free hour)
Oct 25  043 (2:52), +13
Oct 31  048 (3:11), +14

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NTA - N. Taurids velocity 29 km/sec (Antihelion speed, medium slow)

Early October Video Positions

UT Date, RA in degrees, then (Hr:mm), Declination
Oct 8   021 (1:24), +13 (start of video detected activity)
Oct 12  027 (1:49), +14 (last morning before full moon, after this use
                          IMO working list positions)

IMO Working List positions

UT Date, RA in degrees, then (Hr:mm), Declination
Oct 1   023 (1:31), +12
Oct 6   027 (1:47), +14
Oct 12  032 (2:06), +15 (last morning with a moon free hour)
Oct 19  037 (2:29), +18 (first evening with moon free hour, video
                          indicated 1st peak)
Oct 25  043 (2:52), +19
Oct 31  048 (3:11), +20

4. Minor Showers EGE and LMI...

Both of these minor showers reach their peaks shortly after the full
moon, thus observing them will be tough, since during the peaks the moon
will practically be living at the radiant position. Since the peak ZHR
is barely above the visually detectable rate even under the best of
circumstances, there’s not much hope for this year. However, if you use
an alignment cord, or plot the meteors, some useful data might be
collected. I will list the activity period and the peak night position.
Both will be very difficult to observe with the timing of the moon. Next
year will be much better.

The EGE radiant is near LM area #4, rising before midnight (Moon very
close during the peak, and )the LMI radiant doesn’t rise until the early
morning hours with the gibbous moon. Not a good year!

EGE - epsilon Geminids velocity 70 km/sec (very fast), ZHR ~ 2
Radiant  is near epsilon GEM, the pointed corner of LM area #4.
Activity period Oct 14 (Full Moon) to Oct 26

UT Date, RA in degrees, then (Hr:mm), Declination
Oct 19  103 (6:52), +27 (Peak on 18th. Video data suggests peak on 20th)
Oct 27  111 (7:24), +27 (End of activity)

LMI - Leo Minorids, velocity 62 km/sec (fast) ZHR ~ 2
Radiant near the feet of the Great Bear (or Plough), rises after midnight

UT Date, RA in degrees, then (Hr:mm), Declination
Oct 19  157 (10:28), +39 (Moon up before radiant)
Oct 23  161 (10:24), +38 (Working list peak 24th, Video peak 22nd)
Oct 27  165 (11:00), +36 (End of activity)

5. DAU - Leftover Aurigids...

As discussed last month, the IMO working list shows the delta Aurigids
as a continuation of the SPE radiant active until October 10th. Recent
video data shows a much shorter period of activity from a radiant almost
15 degrees away. I therefore will list both positions. This is also a
low rate shower but is visible during the moon free early part of the month.

DAU - delta Aurigids, velocity 64 km/sec (fast)
IMO Working List positions - radiant near the eastern point of LM area
#17.

Oct   1  084 (5:37), +49 (Shower Start Sept 18)
Oct   4  088 (5:51), +49 (Working List Peak ZHR~3)
Oct  10  092 (6:08), +49 (End of Activity)

IMO Video data
Radiant halfway between delta AUR and Pollux

Oct   6  099 (6:34), +44 (Start of Activity)
Oct   9  106 (7:03), +46 (Peak)
Oct  12  113 (7:32), +48 (End of Activity)

6. Sky References...

The Full Moon occurs at 20:02 UT on the 14th, almost splitting the month
in half, with New Moons on the 29th of September and 28th of October.
Early morning viewing continues until about the 12th, and evening moon
free hours begin around the 19th. It’s interesting that the moon angles
allow moon free time only a day or two before the Full Moon, but the
moon is up during the entire night for several days afterward.

Of course we now have the brightest star in the sky, Sirius, visible in
the early morning hours, burning at magnitude –1.44

A number of stars near 0 magnitude are in the sky including:
Vega and Betelgeuse +0.0
Capella +0.1
Rigel +0.2
Procyon +0.4

Stars near first magnitude include:
Aldebaran +0.8
Pollux and Deneb +1.2

Castor is +1.6, as well as the brighter two stars in Orion’s belt

The dimmer star in Orion’s belt is +2.0 as is the brightest star in
Aries, while Saiph (the lower left foot of Orion) is +2.1

Epsilon Gem is +3.1

Of course Triangulum is still overhead with three handy stars at +3,
+3.5, and +4

Finally on the dimmer side, the close pair of stars on the southern edge
of Auriga are +4.0 and +4.5

Hopefully that gives you enough stars to help estimate meteor magnitudes!

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 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 October...

October 2008 NAMN Notes
Written by Wayne T. Hally & edited by Mark Davis
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