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(meteorobs) Meteor Activity Outlook for Oct. 17-23, 2003

The moon reaches its last quarter phase on Saturday October 18. At this time
the moon lies ninety degrees west of the sun and rises near 0100 local
daylight time. This weekend the moon will cause some difficulties to those
viewing during the morning hours. Later in the period though, the waning
crescent moon will become less of a nuisance as the illuminated portion
thins and it rises later and later in the morning. The estimated total
hourly rates for evening observers this week should be near three for those
in the Northern Hemisphere and two in the Southern Hemisphere. For morning
observers the estimated total hourly rates should be near twenty four for
those located in the Northern Hemisphere and sixteen for those in the
Southern Hemisphere. 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 listed below are exact for Saturday night/Sunday
morning October 18/19. The radiants do not change greatly day to day so the
given positions may be used during this entire period. Most star atlases
(available at science stores and libraries) 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 location. 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 last rise later in the night. This list also
provides the order of ascending velocity for each radiant with those listed
first usually being much slower than those last on the list. Velocity should
not be the prime factor for shower association as all showers can produce
slow meteors. Slow meteors can be produced from normally swift showers, such
as the Leonids, when meteors appear near the radiant or close to the
horizon. The true velocity is only revealed in shower members seen far from
the radiant and high in the sky.

The Antihelion radiant is now located at 02:24 (041) +15. This area of the
sky is located in southwestern Aries, ten degrees southeast of the second
magnitude star Hamal (Alpha Arietis). Any slow to medium speed meteor from
northeastern Cetus, southwestern Aries or eastern Pisces could be a
candidate for this shower. The radiant is best placed near 0200 local
daylight time when it lies on the meridian and is highest in the sky. At
this time expect to see two shower members per hour from locations north of
the equator and one shower member per hour from south of the equator.

Unlike most of the annual showers the antihelion source is produced by
debris from unknown objects orbiting in a direct motion like the earth.
These objects are most likely asteroids, which produce stony and metallic
debris whose density is much greater than material produced by comets. This
material collides with the earth on the inbound portion of its orbit, before
its closest approach to the sun. Therefore we best see them just after
midnight when we are facing the direction from which this activity appears.
The antihelion source is active all year from an area of the sky nearly
opposite that of the sun. The center of this source will move approximately
one degree eastward per day and travels through many different
constellations over the course of a year. It may make sense to list these
meteors as antihelions or "ANT" but a majority of meteor organizations
prefer that you list them from the constellation in which the radiant is
currently located or the constellation where the shower reaches maximum
activity. Those who report to the IMO should list these meteors as Northern
Taurids (NTA) or Southern Taurids (STA).

The Orionids (ORI) peak on Tuesday morning October 21 with predicted ZHR's
of twenty. Actual rates will most likely be 10-15 Orionids per hour due to
imperfect viewing conditions caused by moonlight. Good rates, in excess of
five shower members per hour, should be present all week long. The radiant
is currently located at 06:16 (094) +16, which places it in northeastern
Orion, four degrees southwest of the second magnitude star Alhena (Gamma
Geminorum). The radiant is best placed near 0400 local daylight time, when
it lies on the meridian and highest in the sky. At 66km/sec., the average
Orionid is swift. What makes this shower interesting is the fact it is
produced by the debris from Halley's Comet, now seventeen years past its
last trip to the inner solar system. Despite this fact the shower is not
affected by the position of the comet and produces fairly stable rates year
after year.

The Delta Aurigids (DAU) peaked on October 10 with predicted ZHR's of two.
This radiant is currently located at 06:52 (103) +27, which places it in
northern Lynx, eighteen degrees northeast of the second magnitude star
Menkalinan (Beta Aurigae). This weekend I would expect very week rates of
less than one shower member per hour. Due to the extreme northern
declination, this shower is only visible from the southern tropics
northward. The radiant is best placed near 0500 when it lies highest in the
sky. At 64km/sec., the average Delta Aurigid is swift.

The Epsilon Geminids (EGE) peak on October 18 with predicted ZHR's of two.
This radiant is currently located at 07:08 (107) +50, which places it in
central Gemini, three degrees northeast of the third magnitude star Epsilon
Geminorum. This weekend I would expect very week rates of perhaps one shower
member per hour. The radiant is best placed near 0500 when it lies highest
in the sky. At 70km/sec., the average Epsilon Geminid is swift with a high
percentage of persistent trains.

The Northern Apex radiant is now located at 07:44 (116) +36. This position
lies in southern Lynx, five degrees northeast of the second magnitude star
Castor (Alpha Geminorum). This area of the sky is best placed for viewing
during the last dark hour before dawn when it lies highest in the sky. This
source should provide at least two meteors per hour for those in the
Northern Hemisphere and less than one per hour for those in the Southern
Hemisphere.

Like the antihelion area, both apex areas are active all year long and
travel approximately one degree eastward per day. Unlike the antihelion
debris, these particles orbit the sun in a retrograde motion opposite that
of the earth and are most likely produced by unknown comets. They strike the
earth after their closest approach to the sun. Since they are moving in
opposite directions these particles strike the earth at tremendous
velocities often creating bright meteors with persistent trains. These
particles strike the earth on the morning side of earth and are best seen
just before morning twilight while the sky is still perfectly dark. This is
not really a "shower" per se, but an artificial radiant created by the
Earth's motion through space. Meteors from both branches are normally
included in the sporadic count. I feel it is a worthy project to see if it
is possible to distinguish these meteors from the normal sporadic
background. On rare occasions there are meteors with a zero inclination that
radiate precisely from the apex point on the ecliptic, exactly 90 degrees
west of the sun. In simplistic terms, these meteors are seldom seen since
the Earth "sweeps clean" much of the material that shares the same orbit as
our planet. Much more material is located just north and south of the
earth's orbit with slightly higher or lower inclinations. This creates the
northern and southern branches of the apex activity.

The Southern Apex source lies exactly 30 degrees south of its northern
counterpart at 07:44 (116) +06. This position lies in Canis Minor only one
degree northeast of the zero magnitude star Procyon (Alpha Canis Minoris).
Like the northern apex, these meteors are best seen toward dawn when the
radiant lies highest above the horizon in a dark sky. Any meteor from
northwestern Hydra, southwestern Cancer, southeastern Gemini or Canis Minor
could be a candidate from this source. Rates would be now close to one per
hour regardless of your location.

The Leo Minorids (LMI) are listed among the radiants of the Dutch Meteor
Society. This is a shower of very short duration with rates in excess of one
per hour for only three nights. The peak rates are predicted to occur near
October 23 with ZHR's of two. On the 23rd, the radiant will be located at
10:48 (162) +37. This position lies in eastern Leo Minor, two degrees east
of the fourth magnitude star Beta Leo Minoris. This area of the sky is best
placed just before dawn when it lies highest above the northeastern horizon
in a dark sky. At 61km/sec., the average Leo Minorid is swift.

The Sporadic rates for the Northern Hemisphere are now near their annual
peak. One would expect to see perhaps six random meteors per hour during the
last hours before dawn from rural observing sites. This estimate and the
estimate for the Southern Hemisphere does not include meteors from the apex
radiants. During the evening hours perhaps three random meteors can be seen
per hour. Rates seen from the Southern Hemisphere would be approximately
four random meteors being seen per hour during the late morning hours and
two during the evening hours. Morning rates are reduced due to moonlight.

Clear Skies!
Robert Lunsford
AMS Operations Manager









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