Meteor Activity Outlook for December 7-13, 2007

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.