(meteorobs) Meteor Activity Outlook for December 15-21, 2006

[Robert Lunsford]

December is the last month of strong activity as seen in the northern
hemisphere. During the first half of the month minor showers are active in
the constellations of Taurus (Antihelions), Monoceros (Monocerotids), Puppis
(Puppid-Velids), Hydra (Sigma Hydrids), and Leo (Coma Berenicids). Strong
sporadic rates continue during the morning hours as long as the moon is
below the horizon. Rates increase significantly with the arrival of the
Geminids during the second week of the month. From the southern hemisphere,
sporadic rates are increasing in strength toward a peak in January. Meteors
from the above minor showers are also well seen from south of the equator.
The Geminids also increase the southern activity, but not nearly to the
extent that is witnessed in the northern hemisphere.

This week the moon reaches its new phase on Wednesday December 20. At this
time the moon will rise and set with the sun and will not be visible in the
night sky. This weekend the waning crescent moon will no be a factor as it
will be too skinny and rise too late to cause any problems for observers.
The estimated total hourly rates for evening observers this week is near
four for those located north of the equator and three for observers south of
the equator. For morning observers the estimated total hourly rates should
be near twenty-five for northern observers and eighteen for those located
south of the equator. These rates assume that you are watching from rural
areas away from all sources of light pollution. The actual rates will also
depend on factors such as personal light and motion perception, local
weather conditions, alertness and experience in watching meteor activity.

The radiant positions listed below are exact for Saturday night/Sunday
morning December 16/17. These positions do not change greatly day to day so
the listed coordinates may be used during this entire period. Most star
atlases (available at science stores and planetariums) will provide maps
with grid lines of the celestial coordinates so that you may find out
exactly where these positions are located in the sky. A planisphere or
computer planetarium program is also useful in showing the sky at any time
of night on any date of the year. Activity from each radiant is best seen
when it is positioned highest in the sky, either due north or south along
the meridian, depending on your latitude. It must be remembered that meteor
activity is rarely seen at the radiant position. Rather they shoot outwards
from the radiant so it is best to center your field of view so that the
radiant lies at the edge and not the center. This method will allow you to
easily trace the path of each meteor back to the radiant (if it is a shower
member) or in another direction if it is a sporadic. Meteor activity is not
seen from radiants that are located below the horizon. The positions below
are listed in a west to east manner in order of right ascension (celestial
longitude). The positions listed first are located further west therefore
are accessible earlier in the night while those listed further down the list
rise later in the night.

These showers are expected to be active this week:

The Antihelion (ANT) radiant is now centered at 06:32 (098) +23. This area
of the sky lies in western Gemini, three degrees west of the third magnitude
star Epsilon Geminorum. This radiant is best placed near 0100 LST when it
lies on the meridian and is highest in the sky. Rates at this time should be
near three per hour as seen from the northern hemisphere and two per hour
for observers located south of the equator. With an entry velocity of 30
km/sec., the average Antihelion meteor would be of medium-slow speed.

The Monocerotids (MON) are currently active from a radiant located at 07:00
(105) +08. This area of the sky is located in eastern Monoceros, ten degrees
northwest of the zero magnitude star Procyon (Alpha Canis Minoris). These
meteors are best seen near 0100 local standard time when the radiant lies
highest above the horizon. This shower is nearly over for 2006 so rates
would now be less than one per hour, no matter your location. At 42 km/sec.
the Monocerotids produce meteors of average velocity.

The Geminids (GEM) peaked on the night of December 13/14. Rates are now near
five per hour and the shower will cease past the weekend. The radiant is
located at 07:40 (115) +33. This area of the sky is located in northern
Gemini, just one degree northeast of the second magnitude star Castor (Alpha
Geminorum). These meteors are best seen near 0200 local standard time when
the radiant lies highest above the horizon. This shower is best suited for
the Northern Hemisphere but some activity can be seen south of the equator
when the radiant culminates low in the northern sky. At 35 km/sec. the
Geminids produce meteors of average velocity.

The Coma Berenicids (COM) peak near December 20 with an average ZHR of five.
The current location of this radiant is 11:40 (175) +25. This area of the
sky is located in a remote area of eastern Leo some ten degrees northwest of
the second magnitude star Denebola (Beta Leonis). This radiant is probably
responsible for the many reports of activity in Leo during the month of
December. These meteors are best seen near 0600 local standard time when the
radiant lies highest above the horizon. At 65 km/sec. the Coma Berenicids
will usually produce meteors of swift velocity.

Sirko Molau's study of video radiants has revealed activity during the
period December 19-24, from an area in northern Virgo. Maximum occurs on
December 20 with the radiant located at 13:28 (202) +09. This position lies
five degrees southeast of the third magnitude star Vindemiatrix (Epsilon
Virginis). This radiant is best placed during the last dark hour before dawn
when it lies highest in a dark sky. It appears that three percent of the
total sporadic activity for the night is related to this radiant. At
62km/sec., the average meteor from this radiant would be swift.

The Ursids (URS) peak on December 23 with an average ZHR of ten. Current
rates would be less than one per hour. The location of this radiant is 14:28
(217) +77. This area of the sky is located in southern Ursae Minor, close to
the orange second magnitude star Kochab (Beta Ursae Minoris). These meteors
are best seen during the last dark hour before dawn when the radiant lies
highest above the horizon. Due to the high northern declination (celestial
latitude), this shower is not visible to observers located south of the
equator. At 33 km/sec. the Ursids will usually produce meteors of medium to
slow velocity. To read more on viewing the Ursid shower visit the AMS
website at: http://www.amsmeteors.org/showers.html#ursids

Sporadic rates have reached the late year plateau for observers located in
the northern hemisphere. One would expect to see perhaps fifteen random
meteors during the last hour before dawn from rural observing sites. During
the first dark hour after the end of evening twilight, perhaps four random
meteors can be seen per hour. Sporadic rates increase as the night
progresses so rates seen near midnight would be near ten per hour. Sporadic
rates seen from the southern hemisphere have passed their annual minimum and
are rising again. One would expect to see approximately twelve random
meteors per hour during the last hour before dawn and three per hour during
the first dark hour after the end of evening twilight. Rates near midnight
would be near eight per hour.

Antihelion (ANT) - 06:32 (098) +23
Northern Hemisphere - 3   Southern Hemisphere - 2

Monocerotids (MON)  07:00 (105) +08
Northern Hemisphere - >1   Southern Hemisphere - >1

Geminids (GEM)  07:12 (108) +33
Northern Hemisphere - 5   Southern Hemisphere - 2

Coma Berenicids (COM)  11:40 (175) +25
Northern Hemisphere - 3   Southern Hemisphere - 2

Epsilon Virginids (EVR)  13:28 (202) +09
Northern Hemisphere - 1   Southern Hemisphere - 1

Ursids (URS)  14:28 (217) +77
Northern Hemisphere - >1   Southern Hemisphere - 0

*For a detailed explanation on the different classes of meteor showers and
other astronomical terms, please visit:
http://www.amsmeteors.org/showers.html#X2006

Clear Skies!
Robert Lunsford
American Meteor Society