(meteorobs) Meteor Activity Outlook for October 25-31, 2008

[Robert Lunsford]

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 new phase on Tuesday October 28th.
At this time the moon will be located near the sun and will not be visible
in the night sky. This weekend the waning crescent moon will not interfere
with meteor observing as it will be thin and will rise during the late dark
morning hours. The estimated total hourly rates for evening observers this
week is near eight for those located in the mid-northern hemisphere (45 N)
and five for those viewing from the mid-southern hemisphere (45 S). For
morning observers the estimated total hourly rates should be near thirty 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.

The radiant positions and rates listed below are exact for Saturday
night/Sunday morning October 25/26. 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
02:52 (043) +19. This position lies in central Aries, ten degrees southeast
of the second magnitude star Hamal (Alpha Arietis). The center of the large
Southern Taurid (STA) radiant lies at 02:52 (043) +13. This position also
lies in southern Aries, fifteen degrees southeast of the second magnitude
star Hamal (Alpha Arietis). The two radiants are separated by slightly over
five 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
0200 local daylight time (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 subdued this activity so it was most likely not noticed. The
secondary peak is predicted to occur near November 13th and will be 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.

The Orionids (ORI) peaked on the morning of October 21st. Rates will now
dwindle until the shower is no longer detectable. The radiant is now located
at 06:32 (98) +16. This position lies in southwestern Gemini, two degrees
southwest 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.

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 09:16 (139) +29. This position
lies in northeastern Cancer, five degrees east of the fourth magnitude star
Iota Cancri. Visual activity is expected to be low, especially since we are
now nearly two weeks past the peak. 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.

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 so that any possible shower members should be
easily identified. This radiant is currently located at 10:56 (164) +37,
which places it on the Leo Minor/Ursa Major border, just north of the faint
star 46 Leo Minoris. 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 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 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.

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)  02:52 (043) +19   Velocity - 29km/sec.
Hourly Rates:  Northern Hemisphere - 3   Southern Hemisphere - 3

Southern Taurids (STA)  02:52 (043) +13   Velocity - 27km/sec.
Hourly Rates:  Northern Hemisphere - 3   Southern Hemisphere - 3

Orionids (ORI)  06:32 (98) +16   Velocity - 66km/sec.
Hourly Rates:  Northern Hemisphere - 5   Southern Hemisphere - 5

Iota Cancrids (ICA)  09:16 (139) +29   Velocity - 67km/sec.
Hourly Rates:  Northern Hemisphere - <1  Southern Hemisphere -<1

Leo Minorids (LMI)  10:56 (164) +37   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