(meteorobs) Meteor Activity Outlook for December 28, 2007-January 3, 2008

[Robert Lunsford]

No matter where you live, the first half of December provides some of the
best meteor activity of the year. In the northern hemisphere the sporadic
rates are still strong plus you can also count on strong activity from the
Geminids, which peak on December 14. There are also several minor radiants
that add a few meteors each hour. All of these centers of activity are
located high in the sky during the early morning hours this time of year.
The night of December 13/14 is no doubt the best night of the year to view
meteor activity. The moon is favorable during this entire period. After the
15th, the shower activity suddenly wanes and a great majority of the
activity seen is sporadic. Approaching Christmas the moon become a major
factor and ruins the maximum of the Ursid shower.

As seen from the southern hemisphere the sporadic rates are increasing
toward a January maximum. Shower rates are also good but the Geminids suffer
a bit from the lower elevation seen from southern locations. Still with the
warmer weather now occurring south of the equator, December is a great time
to view celestial fireworks.

During this period the moon reaches its last quarter phase on Monday
December 31. At this time the moon will be located ninety degrees west of
the sun and will rise near midnight local standard time (LST). This weekend
the waning gibbous moon will be quite bothersome unless your sky is
transparent. Toward the end of this period the waning crescent moon will
become less of a factor with each passing morning. The estimated total
hourly rates for evening observers this week is near three for those located
in the mid-northern hemisphere (45 N) and two for observers from the
mid-southern hemisphere (45 S). For morning observers the estimated total
hourly rates should be near fourteen for those located in the mid-northern
hemisphere (45 N) and ten for those viewing from the mid-southern hemisphere
(45 S). 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. Morning rates are
reduced by moonlight.

The radiant positions and rates listed below are exact for Saturday
night/Sunday morning December 29/30. 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. Viewing there 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.

The following showers are expected to be active this week:

The Earth has now passed the stream of particles produced by comet 2P/Encke,
which gives us the Taurid meteors each autumn. As we enter the month of
December we again recognize the ever present Antihelion (ANT) radiant. This
large, diffuse radiant is now centered at 07:24 (111) +21. This position
lies in central Gemini near the third magnitude star Delta Geminorum. This
area of the sky is best placed on the meridian near 0100 local standard time
(LST). One can expect to see approximately two shower members per hour as
seen from the northern hemisphere and one per hour from south of the
equator. At 30km/sec., the average Antihelion meteor travels slowly through
the skies.

Sirko Molau's study of video radiants has revealed activity during the
period January 3-9, from an area in western Hydra. Maximum occurs on January
4 with the radiant located at 08:32 (128) -13. This position lies fifteen
degrees southwest of the second magnitude star (Alpha Hydrae (AHY)). This
radiant is best placed near 0200 LST when it lies on the meridian and is
highest in the sky. Rates are most likely less than one shower member per
hour no matter your observing location. At 39km/sec., the average meteor
from this radiant would be of average velocity.

Sirko Molau's study of video radiants has also revealed activity during the
period January 1-6, from an area in western Leo. Maximum occurs on January 3
with the radiant located at 09:44 (146) +25. This position lies very close
to the third magnitude star (Epsilon Leonis (ELE)). This radiant is best
placed near 0300 LST when it lies on the meridian and is highest in the sky.
Rates are most likely less than one shower member per hour no matter your
observing location. At 55km/sec., the average meteor from this radiant would
be swift.

The Coma Berenicids (COM) are active from a radiant located at 12:20 (185)
+21. This area of the sky is located in western Coma Berenices, eight
degrees northeast 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. Current rates would be near one shower member
per hour. 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.

The Quadrantids (QUA) reach a ZHR of one on New Year's day. Stragglers from
this shower may be detected as early as December 28. Shower activity will
lie far below the sporadic rates up to January 3. On the 3rd, rates begin to
increase rapidly reaching maximum activity near 0640 UT on January 4. This
timing is good for the Northern Atlantic region including extreme western
Europe and eastern North America. The exact maximum is difficult to catch
under perfect conditions where the shower peaks with the radiant located 
high in
the sky. Most observers will do well seeing rates of fifty Quadrantids per 
hour.
Most of Europe and North America will see maximum rates of less than fifty
per hour. From high northern latitudes some Quadrantid activity may be seen
during the evening hours. A few Quadrantids may be seen from the equator and
low southern latitudes during the small window of time between the rise of
the radiant and the start of morning twilight. At higher southern latitudes
the radiant does not rise until the sky is too bright so no Quadrantid
activity is visible south of approximately 30 degrees south latitude. On
January 4th the radiant is located at 15:20 (230) +49. This area of the sky
is located in an empty portion of northeastern Bootes some twenty degrees
east of the second magnitude star Alkaid (Eta Ursae Majoris). The nearest
bright star is third magnitude Beta Bootis, lying eight degrees to the
southwest of the Quadrantid radiant. On the morning of January 5, the rates
have dropped back below the sporadic background. The ZHR is back down to one
on January 6 and all traces of the shower disappear by January 13. At 49
km/sec. the Quadrantids produce meteors of average to swift velocity. This
shower is also known as the Bootids.

Sporadic rates are now slowly falling for observers in the northern
hemisphere and rising for those located south of the equator. One would
expect to see approximately ten random meteors during the last hour before
dawn from rural observing sites in the mid-northern hemisphere (45 N).
During the first dark hour after the end of evening twilight, perhaps three
random meteors can be seen per hour. As seen from the mid-southern
hemisphere (45 S) late morning rates would now be near eight per hour.
During the first dark hour after the end of evening twilight, perhaps two
random meteors can be seen per hour. Morning rates are reduced due to
moonlight.

Antihelion (ANT) - 07:24 (111) +21   30km/sec.
Northern Hemisphere - 2   Southern Hemisphere - 1

Alpha Hydrids (Non-IMO Shower)  08:32 (128) -13   39km/sec.
Northern Hemisphere - <1   Southern Hemisphere - <1

Epsilon Leonids (Non-IMO Shower)  09:44 (146) +25   55km/sec.
Northern Hemisphere - <1   Southern Hemisphere - <1

Coma Berenicids (COM)  11:32 (173) +26   65km/sec.
Northern Hemisphere - 1   Southern Hemisphere - <1

Quadrantids (QUA)  15:20 (230) +49   49km/sec.
Northern Hemisphere - <1   Southern Hemisphere - <1

*For a detailed explanation on the different classes of meteor showers and
other astronomical terms, please visit:
http://www.amsmeteors.org/showers.html#2007

Clear Skies!
Robert Lunsford
American Meteor Society