(meteorobs) Meteor Activity Outlook for November 29-December 5, 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 13. 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.

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 first quarter phase on Friday
December 5th. At this time the moon will set near midnight local standard
time. Evening rates will be reduced at this time but the stronger morning
hours will be unaffected. This weekend the waxing crescent moon will set
during the early evening hours and will not be too bothersome. The estimated
total hourly rates for evening observers this week is near six for those
located in the mid-northern hemisphere (45 N) and three for those viewing
from the mid-southern hemisphere (45 S). For morning observers the estimated
total hourly rates should be near twenty for those located in the
mid-northern hemisphere (45 N) and fourteen for those viewing from the
mid-southern hemisphere (45 S). Locations between these two extremes would
see activity between the listed figures. 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 November 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 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 occurs on December 6. Little
activity is expected away from the peak night. The radiant is currently
located at 00:56 (014) -52. This position lies in southeastern Phoenix some
seven 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 05:20 (080) +23. This position
lies in eastern Taurus, six degrees south of the second magnitude star El
Nath (Beta Tauri). This area of the sky is best placed on the meridian near
0100 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.

Sirko Molau's study of video radiants has shown that there is an active
radiant located in northeastern Orion this time of year. The radiant is
currently located at 6:12 (093) +16. This position lies five degrees west of
the second magnitude star Alhena (Gamma Geminorum). Current rates should be
near two shower members per hour. These meteors are best seen near 0200 LST
when the radiant culminates on the meridian. At 45 km/sec. the November
Orionids (NOO) produce meteors of medium-swift velocity. Do not confuse this
radiant with the nearby Antihelion shower, which produces slower meteors.
Observers must include these two radiants within their field of view to
properly designate each shower member. This shower has a very similar
radiant position with the better known and much more active Orionids (of
October and early November). Last year I called these the Lambda Orionids,
not knowing the IAU had already listed a designation for this shower.

Surprisingly, Sirko's most recent study of radiant activity using video
methods has shown that the first traces of the Geminids (GEM) begin to
appear on November 23rd. Currently the Geminids should be producing one
meteor per hour from a radiant located at 06:32 (098) +33. This position
lies in southeastern Auriga, fifteen 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 in a dark sky. At 35 km/sec.
the Geminids produce mostly medium speed meteors.

The Sigma Hydrids (HYD) are active from a radiant located at 07:56 (119)
+05. This position lies in eastern Canis Minor, three degrees east of the
zero magnitude star Procyon (Alpha Canis Minoris). These meteors are best
seen near 0400 LST when the radiant lies highest above the horizon in a dark
sky. At 60 km/sec. the Sigma Hydrids produce mostly swift meteors.

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
08:00 (120) -45. This position lies in eastern Puppis, three degrees north
of the second magnitude star Gamma Velorum. Peak rates occur near December
6. 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.

As seen from the mid-northern hemisphere (45N) one would expect to see
approximately sixteen Sporadic meteors per hour during the last hour before
dawn as seen from rural observing sites. Evening rates would be near four
per hour. As seen from the mid-southern hemisphere (45S), morning rates
would be near eight per hour as seen from rural observing sites and two per
hour during the evening hours. Locations between these two extremes would
see activity between the listed figures.

The table below presents a summary of the expected activity this week. Rates
and positions are exact for Saturday night/Sunday morning but may be used
all week.

Phoenicids (PHO)  00:56 (014) -52   Velocity - 22km/sec.
Northern Hemisphere - <1 Southern Hemisphere - <1

Antihelion (ANT)   05:20 (080) +23  Velocity - 30km/sec.
Northern Hemisphere - 3 Southern Hemisphere - 2

November Orionids (NOO)  06:12 (093) +16   Velocity - 45km/sec.
Northern Hemisphere - 2 Southern Hemisphere - 2

Geminids (GEM)  06:32 (098) +33  Velocity - 35km/sec.
Northern Hemisphere - 1 Southern Hemisphere - <1

Sigma Hydrids (HYD)  07:56 (119) +05  Velocity - 60km/sec.
Northern Hemisphere - <1 Southern Hemisphere - <1

Puppid-Velids (PUP) 08:00 (120) -45  Velocity - 40km/sec.
Northern Hemisphere - <1 Southern Hemisphere - 2

*For a detailed explanation on the different classes of meteor showers and
other astronomical terms, please visit:
http://www.amsmeteors.org/showers.html#X2008

Clear Skies!
Robert Lunsford
American Meteor Society