(meteorobs) Meteor Activity Outlook for November 16-22, 2007

[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 but the sporadic rates are much lower than those seen in
the northern hemisphere.

During this period the moon reaches it first quarter phase on Saturday
November 17. At this time the moon will be located ninety degrees east of
the sun and will set near midnight local standard time. During the latter
portion of this period the waxing gibbous moon will start to hamper
observing as the window between moonset and the start of morning twilight
lessens. The estimated total hourly rates for evening observers this week is
near three for those located in the mid-northern hemisphere (45 N) and one
for observers from the mid-southern hemisphere (45 S). For morning observers
the estimated total hourly rates should be near twenty five 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. Evening rates are reduced due to moonlight.

The radiant positions and rates listed below are exact for Saturday
night/Sunday morning November 17/18. 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 Northern Taurid (NTA) radiant is now centered at 04:12 (063) +24. This
position lies in northern Taurus, five degrees east of the famous naked eye
star cluster known as the Pleiades or Seven Sisters. The Southern Taurid
(STA) radiant lies at 04:08 (062) +16. This position lies five degrees west
of the first magnitude orange star Aldebaran (Alpha Tauri). The two radiants
are separated by seven degrees. Since they have the nearly 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. At 29 and 27 km/sec., the average
Taurid meteor travels slowly through the skies.

Sirko Molau's study of video radiants has revealed a radiant located at 5:00
(075) +30 active between November 15-20. This position lies in the extreme
southeast corner of Auriga, four degrees south of the third magnitude star
Iota Aurigae. This position is close to the radiant of the North Taurids so
care must be taken to differentiate between these radiants. These meteors
are best seen near 0100 Local Standard Time (LST) when the radiant lies
highest above the horizon in a dark sky. Maximum activity occurs on the
17th. Rates are expected to be low but further investigation of this radiant
is needed. At 35 km/sec. the Iota Aurigids produce meteors of average
velocity.

Video data has also shown that activity from northern Orion begin appearing
on November 17 from a radiant located at 5:28 (082) +15. This position lies
five degrees north of third magnitude Lambda Orionis. Current rates would be
low, most likely less than one per hour. These meteors are best seen near
0200 Local Standard Time (LST) when the radiant culminates on the meridian.
Maximum activity occurs on the 28th. At 42 km/sec. the Lambda Orionids
produce meteors of average velocity.

The Alpha Monocerotids (AMO) reach maximum activity on November 22 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 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) are predicted to peak on November 18 from a radiant
located at 10:12 (153) +22. This position lies in western Leo, within the
"Sickle" and very close to the position of the third magnitude star Algeiba
(Gamma Leonis). The radiant is best placed during the last hour before dawn
when it lies highest in a dark sky. Rates at maximum are difficult to
predict but they should range this year anywhere from ten to thirty shower
members per hour. Recent studies of video data by Sirko Molau has indicated
that the Leonids are active longer than expected, with ZHR's of at least one
through November 28. At 70km/sec., the average Leonid is swift with a high
percentage of trains.

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
three random meteors can be seen per hour. As seen from the mid-southern
hemisphere (45 S) late morning rates would now be near six per hour. During
the first dark hour after the end of evening twilight, perhaps one random
meteor can be seen per hour. Moonlight interferes with evening rates

Northern Taurid (NTA)  04:12 (063) +24
Northern Hemisphere - 2   Southern Hemisphere - 1

Southern Taurid (STA)  04:08 (062) +16
Northern Hemisphere - 1   Southern Hemisphere - <1

Iota Aurigids (IAU)  05:00 (075) +30
Northern Hemisphere - <1   Southern Hemisphere - <1

Lambda Orionids (LOR)  05:28 (082) +15
Northern Hemisphere - <1   Southern Hemisphere - <1

Alpha Monocerotids (AMO)  07:48 (117) +01
Northern Hemisphere - <1   Southern Hemisphere - <1

Leonids (LEO)  10:12 (153) +22
Northern Hemisphere - 5   Southern Hemisphere - 3

*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