(meteorobs) NAMN Notes: January 2008

[meteors at comcast.net]

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NAMN Notes: January 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:

1. Quadrantids: Best Shower of the Year So Far...
2. Other January Activity...
3. For the Advanced Observer...
4. 2008 Outlook...
5. For More Information...


1. Quadrantids: Best Shower of the Year So Far...

The Quadrantids (QUA) are likely the highest rate shower currently
active throughout the year, but are in need of more observations. This
is due to the short peak of activity, January weather, and cold
temperatures in the winter Northern Hemisphere reducing the pool of
observers.

The FWHM (Full Width Half Maximum: i.e. the time the rate is more than
half the peak) is just over 8 hours long, so if it occurs during the
daytime, almost all the activity can be missed. A few hours of clouds
can eliminate the bulk of the meteors.

The IMO gives the activity period from January 1-5, however recent IMO
video observations have suggested an extended period of Dec 31 to
January 12th, so I give early and late positions below to allow
observers to track the shower throughout that time.

It appears there is a wide background shower of faint meteors (r~3.2,
ZHR~7), peaking about a day earlier than the superimposed bright meteors
(r~2.1) that we see on January 4th.

This year’s peak is expected at 0640 UT January 4th, which is 1:40 AM EST.

For the PST zone that’s 10:40 PM on January 3rd. That means that the ZHR
would exceed 1 a minute from about 0230-1045 UT, based on a peak ZHR of
120 per hour. The moon is only 4 days from New, so should not hinder
observations at all. While the radiant in Bootes, near the junction with
Hercules and Draco (where the defunct constellation Quadrans Muralis
used to reside) is circumpolar from 40 degrees North latitude, the
radiant doesn’t rise above 30 degrees until after 2 AM. This means that
the U.S. east coast is one of the better locations to see the shower
this year with highest rates from midnight until dawn. For the west
coast rates will be falling as the radiant is rising. The Quadrantids
are medium fast meteors with a geocentric speed of 41
km/sec.

The parent object of this shower had long been assumed to be comet
96P/Macholz, but recent investigations have shown it to be a degassed
comet body, asteroid 2003 EH1, discovered during the LONEOS search
program on March 6th, 2003. It is possible this object is the lost comet
C/1490 Y1.

The Quadrantid meteoroids have rapidly changing orbital parameters: 1500
years ago they were in an orbit inclined at 13 degrees, with a
perihelion of 0.1 AU, currently the orbit is inclined 72 degrees with
perihelion of 0.78 AU, and in another 1000 years they will reach the
maximum inclination of 76 degrees with perihelion at the earth’s orbit,
1 AU. The current Quadrantids were ejected from 2003 EH1 several hundred
years ago, according to the calculations of Jeremie Vaubaillon.

Here are the radiant positions for the QUA shower. They are for 0 hours
UT on the date indicated. RA is given in degrees and (Hours:minutes),
declination is in degrees. The IMO 2008 shower calendar (see link at the
end of these notes) give a graphical representation of the major shower
locations.

Early start Dec 31: RA 226, (15:05) Dec +50
IMO Start Jan 1: RA 229, Dec (15:15), +50
IMO Peak Jan 4: RA 230, Dec (15:22), +49
IMO End Jan 5: RA 231, Dec (15:24), +49
Late end Jan 12: RA 238, Dec (15:53), +49


2. Other January Activity...

Activity near the Coma Berenicid (COM) radiant continues for much of the
month. These are very fast meteors with entry velocities of ~ 65 kps.
Here are the official IMO radiant positions:

COM January 1: RA 187 (12:27), Dec +20
COM Jan 8 (New Moon): RA 192 (12:50), Dec +17
COM End of activity, Jan 20: RA 202 (13:28), Dec +13

As discussed last month, video data has suggested a complicated
situation for this shower.

The IMO says “The radiant ephemeris of this shower is severely
questioned after the scrutinization of single-station video data showing
a clear radiant with an offset of about 15 degrees to the Working List
positions.” The result is given as “possible COM” in the 2008 shower
calendar.

The IMO recommends the use of the old COM positions for 2007-2008, while
meteors from the “possible COM” position should be noted separately.

This means that for IMO reporting the COM positions listed above should
be used. As to how you should report the following meteors to the NAMN
and the IMO, I will discuss that for each of the possible COM radiants
below.

The first radiant, active from Dec 30 to Jan 6, can use the temporary
designation JLE (January Leonids). It is video database shower #84:

JLE Jan 1: RA 172 (11:28), Dec +25
JLE Jan 6: RA 175 (11:40), Dec +25

The second appears to be very close to the radiant of an IAU shower, so
we can use that designation, JCO (January Coma Berenicids). This is
video database shower 91, and JCO is IAU shower #90. I shall list both
radiants:

JCO (IMO Video shower 91) January 13: RA 189 (12:38), Dec +19
JCO (IMO Video shower 91) January 19: RA 183 (12:11), Dec +18

JCO (IAU shower 90) January 19: RA 185 (12:20), Dec +18
JCO (IAU shower 90) January 23: RA 190 (12:41), Dec +17

All these should be reported to the IMO as SPO, “possible COM” with the
radiant position listed for the day. Once again, you can interpolate
between the positions listed for the other days.

Another source of shower meteors during January is the Antihelion
radiant (ANT). These are the meteors traveling around the sun in the
ecliptic plane catching up to us from behind; the radiant moves about 1
degree eastward each day. It should be realized that this is composed of
many different diffuse sources, so a wide radiant (30 degrees along the
ecliptic, and 15 degrees above and below) should be used. The average
entry speed is 30 km/sec, but there is a wide range which I’ll discuss
later.

The center of the radiant starts the month in Gemini, but spends the
period from the New to Full moon in the constellation of Cancer. When
the dark skies return after the Full Moon whiteout, it is in southern Leo.

Here are the radiant positions (ANT):

Start of Month: RA 113 (7:32), Dec +21 (in Gem)
New Moon Jan 8: RA 120 (8:00), Dec +19 (In Cancer)
First Quarter Jan 15: RA 127 (8:28), Dec +17
Last dark morning Jan 19: RA 131 (8:44), Dec +16
First dark evening Jan 25: RA 138 (9:12), Dec +15 (In Leo)
End of Month Jan 31: RA 144 (9:36), Dec +13

Please see the advanced section below for more details.

The other shower this month is one without much impact on Northern
Hemisphere observers. The alpha Centaurids (ACE) is a minor stream that
has exhibited little activity lately. It should probably be called the
beta Centaurids, since the radiant is closer to that star, but since
alpha has a proper name (Rigel Kentaurus), the shower is known by that
name. From the southernmost U.S., the radiant just begins to rise above
the horizon near civil twilight in the early morning, making scientific
observations impossible. However, you may spot an earthgrazer right
before dawn from Key West; it’s hopeless much further north. Radiant
positions:

IMO Start of Activity, Jan 28: RA 198 (13:12), Dec -57
IMO Peak of Activity, Feb 8: RA 213 (14:12), Dec -60
IMO End of Activity, Feb21: RA 226 (15:04), Dec -63


3. For Advanced Observers...

There are a few subjects of interest for the advanced observer. These
fine details should be left to those with dozens of hours per year for a
considerable period. They require expertise in radiant discrimination
hopefully using some method such as an alignment cord, or plotted, video
or photographic records), and also require at least some experience in
estimating meteor velocity accurately.

IMO video records over the last decade have suggested activity from a
few radiants not on the current IMO Working List of Meteor Showers.

The first of these is Sirko Molau’s IMO video database shower #86,
active from January 1-6, with a peak on the 3rd. This is barely above
the level that can be detected with visual observations. The meteors
have a velocity of around 55 km/sec, so are quite swift. Since the whole
shower is only 5 days long, using the peak radiant of RA 146.2 (9:45),
Dec +25 will suffice. This is very near the star epsilon Leonis so this
shower should be reported to the IMO as sporadic (SPO) with a comment
listing the radiant position and the designation ELE. Meteors reported
to the NAMN as ELE will be recorded as such in our database, while they
will be submitted to the IMO as SPO, with appropriate comments.

The second is Sirko Molau’s IMO video database shower #89. These are
medium speed meteors (39 km/sec) from a radiant along the Pyxis/Hydra
border. Active only from the 3rd to the 9th, again the peak radiant
position of RA 128 (8:32), Dec -18 should suffice as far as position.
Report them to the NAMN as PYX (Pyxids) to differentiate from the
background sporadics. Report them to the IMO as sporadics (SPO) with
comments identifying them as PYX and listing the radiant position.

ANTIHELION METEORS: Another subject worth investigation is the
Antihelion meteors. Throughout this period, video records have indicated
a few sub-centers within the wide ANT radiant, with some different
characteristics. This might allow the experienced observer to add useful
scientific data. Again, these require very careful shower association to
separate from the general ANT activity.

There are two centers of activity with slow meteors of 28 km/sec,
typical of antihelion meteors. The first is active from 12/31-1/7, the
second from 1/8-1/14. For days between those I provide, you can
interpolate the positions. These should be reported as ANT:

12/31:  RA 105 (7:00), Dec +17
1/7: RA 120 (7:59), Dec +19
This is IMO video database shower #85

1/8: RA 136 (9:05), Dec +24
1/14: RA 128 (8:32), Dec +10
This is IMO video database shower #90

The other two activity centers feature meteors noticeably faster,
between 36 and 39 km/sec. This is faster than the antihelion speed of ~
30 kps by enough that it should be possible to pick them out.

The first radiant, active from the 2nd to the 7th, is aligned near the
position of the DCA (delta Cancrid) shower, formerly on the IMO working
list, now absorbed by the ANT radiant. However, these meteors cannot be
from the same source, since all photographic evidence for the DCA shower
had velocities of less than 27 km/sec, while the video data for this
radiant indicates a speed of 39 km/sec, nearly 45% faster. As this
radiant is closer to the star iota, I suggest referring to these meteors
as ICA (iota Cancrids). They should be reported to the IMO as ANT, with
a description of the radiant position in the comments. You can report
them to the NAMN as ICA, if you do not report directly to the IMO. We
will make the necessary adjustments when we forward your data.

ICA Jan 2: RA 131 (8:43), Dec +31
ICA Jan 7: RA 131 (8:43), Dec +23

The second radiant, active from Jan 27th through Feb 5th, features
meteors a bit slower at 36 kps, still 20% faster than the typical
antihelion. It is closest to rho Leonis at the peak on Feb 5, so I
suggest referring to them as RLE. Once again, they should be reported to
the IMO as ANT, with radiant position in the comment section.

RLE Jan 27: RA 154 (10:17), Dec +16
RLE Feb 5: RA 157 (10:28), Dec +9

I’d like to remind everyone that these 3 letter codes I suggest are not
official. They are a means to allow us to record data about these
specific showers. Should the IMO create official titles for these
radiants, at least we will have the information preserved, and we can
convert the shower names as required.


4. 2008 Outlook...

Unfortunately, we will spend much of 2008 battling the moon for the
major showers. This situation occurs about every 3 years since there are
just over 12 1/3 lunar cycles per year.

Moon free showers include the ETA (eta Aquarids), SDA (Southern delta
Aquarids), GIA (Draconids), most of the Taurids (STA, NTA), and the URS
Ursids) which could feature an outburst this year. The Perseids (PER)
will only have a few early morning moon free hours. The Orionids (ORI)
and Leonids (LEO) will be bothered by a waxing moon in the sky at the
same time as the radiant, and the Geminid (GEM) peak will share the sky
with the Full Moon.

Therefore we will spend some time this year covering the how and why of
observing the minor showers that will be active during the moon free
intervals.


5. 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

Magnitude references for mid month:

Sirius: -1.4
Mars (in Taurus): -1.3
Betelgeuse, Rigel, and Arcturus: 0 magnitude
Saturn (in Leo) and Procyon: +0.5
In Leo, Regulus the brightest star +1.4, Denebola (the hindquarters) +2.1
The brightest star in Corona Borealis, Alphecca: +2.2
Epsilon Gem (the corner of LM counting area 4) +3

For comments and questions, you may contact us at the addresses below.

Happy observing!!


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 January...

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