(meteorobs) Meteor Activity Outlook for Meteor Activity Outlook for October 18-24, 2008

Robert Lunsford lunro.imo.usa at cox.net
Thu Oct 16 15:11:16 EDT 2008


Meteor activity in general increases in October when compared to September.
A major shower (the Orionids) is active most of the month along with several
minor showers. Both branches of the Taurids become more active as the month
progresses, providing slow, graceful meteors to the nighttime scene. The
Orionids are the big story of the month reaching maximum activity on the
21st. This display can be seen equally well from both hemispheres which
definitely helps out observers located in the sporadic-poor southern
hemisphere this time of year.

During this period the moon reaches its last quarter phase on Tuesday
October 21st. At this time the moon will rise near 0100 local daylight time
and will remain in the sky the remainder of the morning. This weekend the
waning gibbous moon will make meteor watching difficult. Some slow meteors
may be glimpsed during the evening hours before the moon rises, but rates at
this time of night will be low. 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 five for those located in the mid-northern hemisphere
(45 N) and fifteen 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 reduced due to moonlight.

The radiant positions and rates listed below are exact for Saturday
night/Sunday morning October 18/19. 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. Although
the radiants actually lie in Aries during October, they reach maximum
activity in November when they are situated in the constellation of Taurus.

The center of the large Northern Taurid (NTA) radiant is now centered at
02:28 (037) +18. This position lies in central Aries, six degrees southeast
of the second magnitude star Hamal (Alpha Arietis). The center of the large
Southern Taurid (STA) radiant lies at 02:36 (039) +12. This position also
lies in southern Aries, twelve degrees southeast of the second magnitude
star Hamal (Alpha Arietis). The two radiants are separated by slightly over
five degrees. Since they have 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. These radiants are best placed near the meridian at
0200 LDT. 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 will subdue this activity so it will most likely not be
noticed. The same study has revealed that the Southern Taurids may peak
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.

The Orionids (ORI) peak on the morning of October 21st from a radiant
located at 06:20 (95) +16. This position lies in extreme eastern Orion, four
degrees west of the second magnitude star Alhena (Gamma Geminorum). The
radiant rises near 2300 LDT and is best placed on the meridian near 0500. At
66km/sec., the average Orionid is swift. A detailed discussion of the
Orionids with charts is presented on the AMS website at:
http://www.amsmeteors.org/showers.html#ORI

The Epsilon Geminids (EGE) peak on October 18 radiant with a average ZHR of
only two. Rates near maximum can vary sometimes reaching in excess of five.
The radiant is currently located at 06:56 (104) +27. This position lies in
central Gemini, three degrees northeast of the third magnitude star Epsilon
Geminorum. Current rates will be most likely less than one per hour,
especially with the bright moon in the sky. At 70km/sec., the average
Epsilon Geminid is swift. Sirko Molau's new studies of video radiants has
also revealed that the Epsilon Geminids may peak as late as October 21st.

Sirko Molau's studies of video radiants has revealed activity in northern
Cancer between October 10 and November 4, peaking on the October 14th. The
radiant for the Iota Cancrids (ICA) lies at 09:00 (135) +29. This position
lies two degrees east of the fourth magnitude star Iota Cancri. Visual
activity is expected to be low, especially with the bright moon in the
morning sky. The radiant rises near 0200 LDT and is best placed high in the
east during the last dark hour of the morning. At 67km/sec., the average
Iota Cancrid will appear move swiftly through the skies.

Another radiant discovered during Sirko Molau's studies of video radiants Is
the Tau Ursa Majorids (TUM). This shower is active between October 15th and
the 22nd, peaking on the 16th. The radiant lies at 09:36 (144) +65. This
position lies in western Ursa Major near the faint star 23 Ursae Majoris.
Again visual activity is expected to be low with the bright moon in the
morning sky. The radiant is circumpolar north 25 degrees north latitude and
is best seen during the last hour before dawn when it lies highest above the
horizon in a dark sky. At 54km/sec., the average Tau Ursa Majorid meteor
will appear move swiftly through the skies.

The Leo Minorids (LMI) are active from October 17-27 with maximum activity
occurring on October 23rd. ZHR's are usually low but the radiant is far
removed from the Orionids and Epsilon Geminids so that any possible shower
members should be easily identified. This radiant is currently located at
10:28 (157) +39, which places it on the Leo Minor/Ursa major border, just
south of a pair of third magnitude stars known as Mu and Lambda Ursae
Majoris. The radiant is best placed just before dawn when it lies highest in
a dark sky. This shower is better situated for observers situated in the
northern hemisphere where the radiant rises far higher into the sky before
the start of morning twilight. At 62km/sec., the average Leo Minorid is
swift.

As seen from the mid-northern hemisphere (45N) one would expect to see
approximately twelve 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 four 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 reduced during
this period due to the bright moon.

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)  02:28 (037) +18   Velocity 29km/sec.
Hourly Rates: Northern Hemisphere  2 - Southern Hemisphere 2

Southern Taurids (STA)  02:36 (039) +12   Velocity 27km/sec.
Hourly Rates: Northern Hemisphere  3 - Southern Hemisphere 3

Orionids (ORI)  06:20 (95) +16   Velocity 66km/sec.
Hourly Rates: Northern Hemisphere  5 - Southern Hemisphere 5

Epsilon Geminids (EGE)  06:56 (104) +27   Velocity 70km/sec.
Hourly Rates: Northern Hemisphere  <1 - Southern Hemisphere <1

Iota Cancrids (ICA)  09:00 (135) +29   Velocity 67km/sec.
Hourly Rates: Northern Hemisphere  1 - Southern Hemisphere <1

Tau Ursa Majorids (TUM)  09:36 (144) +65   Velocity 54km/sec.
Hourly Rates: Northern Hemisphere  <1 - Southern Hemisphere <1

Leo Minorids (LMI)  10:28 (157) +39   Velocity 62km/sec.
Hourly Rates: 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




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