(meteorobs) Meteor Activity Outlook for December 7-13, 2007

[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 new phase on Sunday December 9. At
this time the moon will be located near the sun and will not visible at
night. Next week the moon will enter the evening sky as a waxing crescent
but will set long before the onset of the best meteor activity. The
estimated total hourly rates for evening observers this week is near four
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 twenty-seven for those located
in the mid-northern hemisphere (45 N) and twenty 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.

The radiant positions and rates listed below are exact for Saturday
night/Sunday morning December 8/9. 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 Phoenicids (PHO) are a periodic shower that rarely produces noticeable
activity. The only impressive display produced by this shower occurred in
1956 when ZHR's were near 100. Peak activity occurred on December 6 so 
little
activity is expected away from the peak night. The radiant is currently
located at 01:24 (021) -53. This position lies in southeastern Phoenix some
five degrees northwest of the bright zero magnitude star Achernar (Alpha
Eridani). These meteors are best seen near 2100 (9pm) local standard time
(LST, regardless of time zone) when the radiant lies highest above the
horizon in a dark sky. Due to the southerly declination of the radiant, this
shower is not visible north of the northern tropical areas. The deep
southern hemisphere has the best chance of seeing any activity. At 22
km/sec. the Phoenicids produce very slow meteors.

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 05:56 (089) +23. This position
lies where the borders of Taurus, Orion, and Gemini meet. The nearest bright
star is third magnitude Eta Geminorum which lies three degrees east of this
position. This area of the sky is best placed on the meridian near 0100
local standard time (LST). One can expect to see approximately three shower
members per hour as seen from the northern hemisphere and two per hour from
south of the equator. At 30km/sec., the average Antihelion meteor travels
slowly through the skies.

The Monocerotids (MON) are currently active from a radiant located at 06:36
(099) +08. This area of the sky is located in northern Monoceros, eight
degrees south of the second magnitude star Alhena (Gamma Geminorum). These
meteors are best seen near 0100 LST when the radiant lies highest above the
horizon. The peak for the Monocerotids is published as December 8 but recent
video studies by Sirko Molau shows a week-long peak of weak activity
commencing on December 6 and ending rather suddenly on the 16th. This shower
would be equally well seen from both hemispheres. Current rates are most
likely near one per hour. At 42 km/sec. the Monocerotids produce meteors of
average velocity.

The Geminids (GEM) are now active and will peak on the night of December
13/14. Rates will rise steadily this week as we approach the date of maximum
activity. Current rates would be near five shower members per hour as seen
from the mid-northern latitudes and only one per hour from the mid-southern
latitudes. The current radiant is located at 07:08 (107) +33. This area of
the sky is located in northern Gemini, six degrees west of the second
magnitude star Castor (Alpha Geminorum). These meteors are best seen near
0200 LST 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. An article on how
to observe and photograph the Geminids is available at:
http://www.amsmeteors.org/showers.html#geminids

The Puppid-Velids (PUP) is a vast complex of weak radiants located in the
constellations of Puppis and Vela. Visual plots and photographic studies
have revealed many radiants in this area during November and December. The
combined strength of these radiants can produce a ZHR of ten. Actual hourly
rates will be much less unless you happen to be observing from the deep
Southern Hemisphere. The center of this activity is currently located at
08:20 (125) -45. This position lies in western Vela, four degrees northeast
of the second magnitude star Gamma Velorum. Peak rates occurred near
December 7. These meteors are best seen near 0300 LST when the radiant lies
highest above the horizon in a dark sky. Observers located in the Southern
Hemisphere have an advantage viewing this shower as the radiant will rise
higher into their sky allowing more activity to be seen. At 40 km/sec. the
Puppid-Velids produce meteors of average velocity.

The Sigma Hydrids (HYD) may be seen from a radiant located at 08:20 (125)
+02. This area of the sky is located in western Hydra, three degrees
southwest of the five faint stars that make up the "head" of Hydra. These
meteors are best seen near 0300 local standard time when the radiant lies
highest above the horizon. The predicted peak for the Sigma Hydrids occurs
on December 12 when the ZHR reaches two. Recent studies have indicated that
this shower may peak earlier in the month so careful monitoring this week of
any activity would be valuable. Current rates are expected to be near one
shower member per hour. At 58 km/sec. the Sigma Hydrids produce meteors of
average to swift velocity.

The Coma Berenicids (COM) are usually noticed a bit later in the month.
Video studies by Sirko Molau have shown that the shower actually begins near
December 5 and peaks on December 20. The current location of this radiant
would near 11:16 (169) +27. This area of the sky is located in northern Leo,
seven degrees north of the third magnitude star Zosma (Delta 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 0500 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.

Sporadic rates have reached maximum for observers in the northern hemisphere
and are now slowly rising for those located south of the equator. One would
expect to see approximately sixteen 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
four random meteors can be seen per hour. As seen from the mid-southern
hemisphere (45 S) late morning rates would now be near ten per hour. During
the first dark hour after the end of evening twilight, perhaps two random
meteors can be seen per hour.


Phoenicids (PHO) 01:24 (021) -53
Northern Hemisphere - <1   Southern Hemisphere - <1

Antihelion (ANT) - 05:56 (089) +23
Northern Hemisphere - 3   Southern Hemisphere - 2

Monocerotids (MON) 06:36 (099) +08
Northern Hemisphere - 1   Southern Hemisphere - 1

Geminids (GEM)  07:08 (107) +33
Northern Hemisphere - 5   Southern Hemisphere - 1

Puppid-Velids (PUP)  08:12 (123) -45
Northern Hemisphere - <1   Southern Hemisphere - 5

Sigma Hydrids (HYD)  08:20 (125) +02
Northern Hemisphere - 1   Southern Hemisphere - 1

Coma Berenicids (COM)  11:16 (169) +27
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