(meteorobs) NAMN Notes: January 2011

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Mon Jan 3 05:28:25 EST 2011


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NAMN Notes: January 2011
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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

By Wayne T. Hally, NJAA


Contents:
1. Quadrantids: Highest ZHR of the Year?...
2. Other January Activity…For the Advanced Observer...
3. Notes...
4. For More Information...


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

The Quadrantids (QUA) are one the highest ZHR showers 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. In
addition, the radiant reaches it’s highest elevation after sunrise, so
observed rates are always lower, and best closest to dawn.

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 December 28-January 12, however
recent IMO video observations have suggested that earlier than Jan. 1
and after Jan. 11, the radiant is very diffuse and doesn’t track the
path of the main period. Also, other than from Jan 4-6, rates are very
low (ZHR <3).

This year’s peak is expected at 0110 UT January 4th, which is 8:10 PM
EST on the 3rd. Jeremie Vaubaillon has suggested a wider range of
possible times from 21 UT on the 3rd to 0600 on the 4th (that end time
is 0100 EST on the 4th). It’s in a much better position for Europe and
Asia where the radiant will be higher in the sky before dawn.

The moon is New, so should not hinder observations at all. The radiant,
in Bootes between the top of the “kite” and Draco’s tail (where the
defunct constellation Quadrans Muralis used to reside) is circumpolar
from 40 degrees North Latitude. However, the radiant doesn’t rise above
30 degrees until after 2 AM, when observed rates under perfectly dark
skies would be half the ZHR.

The Quadrantids are medium fast meteors with a geocentric speed of 41
km/sec according to the IMO working list, but video data suggests that
they fall from 44 to 40 km/sec during the activity period. While not too
significant for the visual observer, it is rather interesting! The video
data also suggests rates might be interesting on the mornings of the 5th
and 6th. Also unusual is the very high inclination of the meteor
stream’s orbit, 72 degrees.

All the above means that the morning of the 4th should be the best time,
with the 5th and 6th worth looking, weather permitting of course.

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

Good magnitude reference stars are nearby, including magnitude +1.4
Regulus and +2.1 Denebola in Leo and the +2, +3, +4, and +5 stars in the
Little Dipper (Actually +2.0 for Polaris, +2.1 for Kochab, +3.0, +4.3
and +5.0).

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 2011 shower calendar (see link at the
end of these notes) gives a graphical representation of these locations,
as well as the ANT and ACE minor showers discussed later.

Start Jan 1:  229 (15:15), +50
Peak Jan 4:  231 (15:25), +49
End Jan 11: 234 (15:38), +49


2. Other January Activity… For Advanced Observers...

Everything else this month stretches the definition of even a “minor”
shower, Even the Antihelion ZHR is 3 at best, and all the others are
lower. Extreme care is needed to discern these shower members from the
sporadic background, which is why I use an alignment cord, and make the
effort to calculate the expected angular velocity before heading out
each night.

The “best” remaining 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.

The center of the radiant starts the month in Gemini, but spends most of
January in Cancer before moving into Leo.

Here are the radiant positions (ANT):

Jan 01: RA 113 (7:32), Dec +21 (in Gem)
Jan 06: 118 (7:52), +20 (In Cancer)
Jan 11: 123 (8:12), +18
Jan 16: 128 (8:32), +17 (early morning dark hours)
Full Moon Period Jan 18-20
Jan 26: 139 (9:16), +15 (In Leo) (early evening dark hours)
Jan 31: 144 (9:36), +13

--------------------------

Also active until Feb 5 is the December Leonis Minorids (DLM), at about
the same rate. It peaked in December and probably has a ZHR no higher
than 2 for the month. These are very fast meteors at 64 km/sec.

Here are the radiant positions (DLM):

Jan 01: RA 172 (11:39), Dec +25
Jan 06: 177 (11:47), +23
Jan 11: 181 (12:03), +21
Jan 16: 185 (12:21), +19 (early morning dark hours)
Full Moon Period Jan 18-20
Jan 26: 193 (12:53), +14 (early evening dark hours)
Jan 31: 198 (13:12), +12

Next is the alpha-Hydrids (AHY). This has long been an IAU shower
(#331), and video data has supported its existence. However, rates are
quite low. The radiant is actually far west of the star Alphard (a-Hya),
almost in Monoceros. It is active from the 1st to the 10th, peaking on
the 1st. The meteors are medium speed, with a velocity of 45 km/sec.

Radiant Positions (AHY)
Jan 01: RA 126 (8:24), Dec -08
Jan 05: 124 (8:16), -08
Jan 10: 121 (8:06), -09

Next is the January Leonids (JLE). The ZHR for this shower makes it
virtually undetectable, but what the heck, the video data shows it does
(barely) exist. The peak, such as it is, occurs on the 2nd, with an
activity period from Jan 1-6. These are fast meteors at 54 km/sec.

Radiant Positions: (JLE)

Jan 01: RA 146 (9:44), Dec +25
Jan 06: RA 149 (9:56), Dec +24

---------

Also detected in the video data is a low rate, short period shower, the
xi-Coronae Borealids (XCB). Only active from the 11th to the 16th, it
will be spotted in the early morning hours after moonset. Velocity is a
fast 50  km/sec.

Radiant Positions: (XCB)

Jan 11: RA 249 (16:37), Dec +30
Jan 16: RA 248 (16:33), Dec +29

-----------

The final 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 is better known (Rigel Kentaurus), the shower is called by that
name. From the southernmost US, the radiant just begins to rise above
the horizon near twilight in the early morning, making scientific
observations impossible. However, you may spot an earthgrazer right
before dawn from Key West and Hawaii; it’s hopeless much further north.
Velocity is high at 56 km/sec.

Radiant positions:

Start of activity Jan 28: RA 198 (13:12), Dec -57


3. Notes...

When I say “video” in the NAMN discussions, the primary reference is the
article in WGN 37:4 titled “A comprehensive list obtained from 10 years
of observations with the IMO Video Meteor Network”, by Sirko Molau and
Jurgen Rendtel. It included almost half a million meteors over more than
100,000 hours Teff from 1993 to 2009. This was used as much of the basis
for the changes in the 2011 IMO (International Meteor Organization)
Working List. Modifications were made to many shower’s start and end
dates, and radiant positions.

Also, in WGN 38:5, an analysis of activity near Auriga and Perseus for
September and October was published; more on that at the end of the summer.


4. For More Information...

For radiant positions and more detailed descriptions of showers, see the
IMO 2011 Meteor Shower Calendar at:
http://www.imo.net/calendar/2011

Magnitude references for mid-month:
Sirius: -1.4
Betelgeuse, Rigel, and Arcturus: ~0 magnitude
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!!

If you contact me, I can send you an Excel worksheet with day by day
radiant positions and shower member velocities (for those that vary),
based on the latest available data.


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' NAMN email: namn at namnmeteors.org

NAMN website: http://www.namnmeteors.org

Kevin Kilkenny, namnfireball at earthlink.net
Staten Island, New York, USA
Coordinator, Fireballs and Meteorites

Mark Davis, meteors at comcast.net
Goose Creek, South Carolina, USA
Coordinator, North American Meteor Network

Back issues of NAMN Notes can be found online at 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...
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January 2011 NAMN Notes




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