(meteorobs) Meteor Activity Outlook forNovember 22-28, 2008

[Robert Lunsford]

As seen from the northern hemisphere, meteor rates continue to be strong in
November. While no major showers are active this month, the two Taurid
radiants plus the Leonids keep the skies active. The addition of strong
sporadic rates make November one of the better months to view meteor
activity from north of the equator. Skies are fairly quiet as seen from the
southern hemisphere this month. Activity from the three showers mentioned
above may be seen from south of the equator, but the sporadic rates are much
lower than those seen in the northern hemisphere.

During this period the moon reaches its new phase on Thursday November 27th.
At this time the moon will rise and set with the sun and will not be visible
at night. This weekend the waning crescent moon will rise during the late
morning hours and will not be too bothersome. The estimated total hourly
rates for evening observers this week is near five for those located in the
mid-northern hemisphere (45 N) and two 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 ten 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. Morning
rates are slightly decreased due to moonlight.

The radiant positions and rates listed below are exact for Saturday
night/Sunday morning November 22/23. 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:

At this time of year debris from comet 2P/Encke produces a double radiant
very close to the position of the antihelion radiant. From now through the
end of November, it is impossible to resolve the antihelion meteors from
those produced by comet 2P/Encke. Therefore we suggest that observers simply
classify meteors from this area as either north or south Taurids.

The center of the large Northern Taurid (NTA) radiant is now centered at
04:32 (068) +24. This position lies in central Taurus, eight degrees north
of the orange first magnitude star Aldebaran (Alpha Tauri). The center of
the large Southern Taurid (STA) radiant lies at 04:36 (069) +17. This
position also lies in central Taurus, only one degree north of Aldebaran.
The two radiants are separated by approximately seven degrees. Since they
have the same right ascension (celestial longitude), it is difficult to
distinguish meteors that move north or south out of the radiants. It is less
difficult to distinguish those meteors traveling east or west. These
radiants are best placed near the meridian at 0100 LST (Local Standard
Time). At 29 and 27 km/sec., the average Taurid meteor travels slowly
through the skies.

Sirko Molau's new studies of video radiants has revealed that the Northern
Taurid's reach two plateaus of activity with the first occurring on October
20th. The moon subdued this activity so it was most likely not noticed. The
secondary peak was predicted to occur near November 13th and was severely
hampered by a bright moon. The same study has revealed that the Southern
Taurids may have peaked near October 11 and that the activity for this
shower will remain fairly constant through the first week of November. After
that rates will dwindle until these meteors disappear near the end of
November.

Sirko Molau's study of video radiants has shown that activity from northern
Orion begins to appear on November 18 from a radiant located at 5:44 (086)
+15. This position lies seven degrees northwest of the orange first
magnitude variable star Betelgeuse (Alpha Orionis). Current rates should be
near one shower member per hour. These meteors are best seen near 0200 LST
when the radiant culminates on the meridian. Maximum activity occurs on the
28th when several meteors per hour should be visible. At 45 km/sec. the
November Orionids (NOO) produce meteors of medium-swift velocity. 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. At this time the radiant is located at 06:04 (091)
+34. This position lies in southeastern Auriga, three degrees southeast of
the third magnitude star Theta Aurigae. These meteors are best seen near
0200 LST when the radiant lies highest above the horizon in a dark sky.
Since we are a full three weeks before maximum, rates would be low, most
likely less than one per hour. At 35 km/sec. the Geminids produce mostly
medium speed meteors.

The first traces of the Sigma Hydrids (HYD) begin to appear on November
22nd. At this time the radiant is located at 07:28 (112) +07. This position
lies in central Canis Minor, two degrees west 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 Alpha Monocerotids produce mostly swift meteors.

The Alpha Monocerotids (AMO) reach maximum activity on November 21st with
normally low rates of one or two shower members per hour. This shower has
produced outbursts in the past but none are expected for many years to come.
The radiant is located at 07:48 (117) +01. This position lies in
southeastern Canis Minor, five degrees southeast of the zero magnitude star
Procyon (Alpha Canis Minoris). These meteors are also best seen near 0400
LST when the radiant lies highest above the horizon in a dark sky. At 65
km/sec. the Alpha Monocerotids produce mostly swift meteors.

The Leonids (LEO) peaked over Europe on the morning of November 17th. Rates
are now falling and the last members of the Leonid shower will be seen up to
November 28th. Hourly rates will be near one this weekend and then less than
one the remainder of the week. The radiant is currently located at 10:20
(155) +19. This position lies in western Leo, only one degree southwest of
the famous orange double star Algeiba (Gamma Leonis). At 71km/sec., the
average Leo is swift with a high percentage of trains. The radiant is most
favorably located during the last dark hour before the onset of morning
twilight.

As seen from the mid-northern hemisphere (45N) one would expect to see
approximately fourteen 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 five per hour as seen from rural observing sites and one per
hour during the evening hours. Locations between these two extremes would
see activity between the listed figures. Morning rates are slightly reduced
during this period due to moonlight.

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.

Northern Taurids (NTA)  04:32 (068) +24   Velocity 29km/sec
Hourly Rate - Northern Hemisphere - 2   Southern Hemisphere - 2

Southern Taurids (STA)  04:36 (069) +17   Velocity 27km/sec
Hourly Rate - Northern Hemisphere - 1   Southern Hemisphere - 1

November Orionids (NOO)  05:44 (086) +15   Velocity 45km/sec
Hourly Rate - Northern Hemisphere - 1   Southern Hemisphere - 1

Geminids (GEM)  06:04 (091) +34   Velocity 35km/sec
Hourly Rate - Northern Hemisphere - <1   Southern Hemisphere - <1

Sigma Hydrids (HYD) 07:28 (112) +07   Velocity 60km/sec
Hourly Rate - Northern Hemisphere - <1   Southern Hemisphere - <1

Alpha Monocerotids (AMO)  07:48 (117) +01   Velocity 65km/sec
Hourly Rate - Northern Hemisphere - <1   Southern Hemisphere - <1

Leonids (LEO) 10:20 (155) +19   Velocity 71km/sec
Hourly Rate - 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#X2008

Clear Skies!
Robert Lunsford
American Meteor Society