(meteorobs) Meteor Activity Outlook for October 11-17, 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 full phase on Tuesday October 14th.
At this time the moon will rise near sunset and set near sunrise and will be
in the sky all night long. This weekend there will be a small window of
darkness between moonset and morning twilight when observing can be
attempted under good conditions. 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 fifteen for those located in the mid-northern
hemisphere (45 N) and five 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 listed rates are reduced due to moonlight.

The radiant positions and rates listed below are exact for Saturday
night/Sunday morning October 11/12. 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:

Sirko Molau's studies of video radiants has revealed activity in Ursa Minor
between October 10 and 16, peaking on the 12th. The position at maximum
activity is 16:32 (248) +82. This position lies in central Ursa Minor near
the faint star Epsilon Ursae Minoris. Visual activity is expected to be low,
but detectable. The radiant is best placed as soon as it becomes dark during
the evening hours. Due to the high northern declination (celestial latitude)
this activity is invisible from the southern hemisphere. At 35km/sec., the
average Epsilon Ursae Minorid (EUM) will appear as medium-slow.

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
02:04 (031) +15. This position lies in southwestern Aries, eight degrees
south of the second magnitude star Hamal (Alpha Arietis). The center of the
large Southern Taurid (STA) radiant lies at 02:12 (033) +09. This position
also lies in southwestern Aries, five degrees south 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.

The Orionids (ORI) are now becoming more active from a radiant located at
05:56 (89) +15. This position lies in northeastern Orion, seven degrees
north of the orange first magnitude star Betelgeuse (Alpha Orionis). The
radiant rises near 2300 LDT and is best placed on the meridian near 0500.
With maximum activity predicted for October 21, current rates for all
locations would be near two to three per hour as seen after midnight. At
66km/sec., the average Orionid is swift.

The Epsilon Geminids (EGE) reach a ZHR of one on October 14th. The radiant
is located at 06:24 (096) +27. This position lies in western Gemini, three
degrees northwest of the third magnitude star Epsilon Geminorum. Maximum
activity is predicted to occur on October 18 with an average ZHR of two.
Current rates will be most likely less than one per hour. At 70km/sec., the
average Epsilon Geminid 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 08:44 (131) +29. This position
lies very close to the fourth magnitude star Iota Cancri. Visual activity is
expected to be low, especially with the moon nearing it's full phase. After
this weekend observers will not get a chance to view this activity under
dark skies until late in the month. 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 Ursae 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 moon nearing it's full
phase. 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 Ursae Majorid meteor
will appear move swiftly through the skies.

As seen from the mid-northern hemisphere (45N) one would expect to see
approximately ten Sporadic meteors per hour during the last hour before dawn
as seen from rural observing sites. Evening rates would be near three per
hour. As seen from the mid-southern hemisphere (45S), morning rates would be
near three 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. 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.

Epsilon Ursae Minorids (EUM)   16:32 (248) +82   Velocity km/sec. 35
Northern Hemisphere -  <1   Southern Hemisphere - 0

Northern Taurids (NTA)   02:04 (031) +15   Velocity 29km/sec.
Northern Hemisphere -  1   Southern Hemisphere - 1

Southern Taurids (STA)  02:12 (033) +09   Velocity 27km/sec.
Northern Hemisphere -  2   Southern Hemisphere - 2

Orionids (ORI)   05:56 (89) +15   Velocity 66km/sec.
Northern Hemisphere -  2   Southern Hemisphere - 2

Epsilon Geminids (EGE)  06:24 (096) +27   Velocity 70km/sec.
Northern Hemisphere -  <1   Southern Hemisphere - <1

Iota Cancrids (ICA)  08:44 (131) +29   Velocity 67km/sec.
Northern Hemisphere -  <1   Southern Hemisphere - 0

Tau Ursae Majorids (TUM)  09:36 (144) +65   Velocity 54km.sec.
Northern Hemisphere -  <1   Southern Hemisphere - 0

*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