[Meteorobs] Meteor Activity Outlook for October 19-25, 2007

[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 in the sporadic-poor southern skies this time of year.

During this period the moon reaches it first quarter phase on Friday October
19. At this time the moon sets near midnight local daylight time leaving the
prime morning hours free of interfering moonlight. As the period progresses
the window of dark skies shrinks as the moon sets later in the morning sky.
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 fifty for those located in the
mid-northern hemisphere (45 N) and thirty 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. Moonlight interferes with evening rates.

The radiant positions and rates listed below are exact for Saturday
night/Sunday morning October 20/21. 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 Northern Taurid (NTA) radiant is now centered at 02:36 (039) +18. This
position lies in central Aries, eight degrees southeast of the second
magnitude star Hamal (Alpha Arietis). The Southern Taurid (STA) radiant lies
at 02:40 (040) +12. This position lies in southern Aries, two degrees
northwest of the fourth magnitude star Mu Ceti. 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. At 29 and 27 km/sec.,
the average Taurid meteor travels slowly through the skies.

The Orionids (ORI) peak on Sunday morning October 21 with a radiant located
at 06:20 (095) +16. This position lies in northeastern Orion, three 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. The
Orionids are normally faint and difficult to view from urban locations. It
is advised to find a safe rural location to view this display at its best.
To see the best rates be sure to wait until the moon has set. Rates peaked
near 60 per hour last year and are expected to be better than normal again
this year. The Orionids have a "plateau-like" peak therefore rates are still
good on the mornings before and after the expected maximum. At 66km/sec.,
the average Orionid meteor is swift.

Sirko Molau's studies of video radiants has revealed activity in Monoceros
between October 17 and 26, peaking on the 24th. The position at maximum
activity is 6:56 (104) +11. This position lies in northeastern Monoceros,
three degrees southeast of the third magnitude star Xi Geminorum. Visual
activity is expected to be low, but detectable. This radiant is very close
to the Orionid radiant therefore distinguishing these meteors from the
Orionids will be difficult at best. The radiant is best placed near 0600
local daylight time. At 59km/sec., the average Xi Geminid will appear as
swift.

The Epsilon Geminids (EGE) are active from a radiant located at 07:00 (105)
+27. This position lies in central Gemini, four degrees northeast of the
third magnitude star Epsilon Geminorum. Maximum activity occurred on October
18 with an expected ZHR of two. Current rates will be most likely be near
one per hour. Recent studies of video data by Sirko Molau has indicated that
this shower is more active earlier in the month with a maximum occurring on
October 14. Weaker rates occurring now would indicate the earlier maximum is
correct. At 70km/sec., the average Epsilon Geminid is swift. Be careful not
to confuse these meteors with the far more numerous Orionids. Including
both radiants within your field of view would help prevent this problem.

The Leo Minorids (LMI) are active for only one week centered on October 24.
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 10:56 (164) +37, which
places it on the Leo Minor/Ursa major border, four degrees north of the
fourth magnitude 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.

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 five 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) 02:36 (039) +18
Northern Hemisphere - 2 Southern Hemisphere - 1

Southern Taurid (STA) 02:40 (040) +12
Northern Hemisphere - 2 Southern Hemisphere - 1

Orionids (ORI) 06:20 (095) +16
Northern Hemisphere - 25 Southern Hemisphere - 25

Xi Geminids (XGE) 6:56 (104) +11
Northern Hemisphere - <1 Southern Hemisphere - <1

Epsilon Geminids (EGE) 07:00 (105) +27
Northern Hemisphere - 1 Southern Hemisphere - >1

Leo Minorids (LMI) 10:56 (164) +37
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#2007

Clear Skies!
Robert Lunsford
American Meteor Society