(meteorobs) Meteor Activity Outlook for September 9-15, 2005

[Robert Lunsford]

This upcoming period will see the moon reaching its first quarter phase on
Sunday September 11. At this time the moon will set near 0100 local daylight
time. This will still allow good viewing conditions during the morning
hours. The estimated total hourly rates for evening observers this week
should be near four for Northern Hemisphere observers and two for those
located in the Southern Hemisphere. For morning observers the estimated
total hourly rates should be near fourteen for Northern Hemisphere observers
and eight for those located 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. Evening rates are reduced due to
moonlight.

The radiant positions listed below are exact for Saturday night/Sunday
morning September 10/11 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. 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.

These are the showers that may be observed this week:

The Kappa Aquarids (KAQ) are listed among the radiants of the Dutch Meteor
Society. At peak activity (September 18) this radiant only produces a ZHR of
three. Current rates would most likely less than one shower member per hour.
The radiant is located in western Aquarius at 22:08 (332) -08. This position
is located two degrees west of the fourth magnitude star Theta Aquarii. The
radiant is best placed for viewing near midnight local daylight time, when
the radiant lies highest in the sky. At 19km/sec., the average Kappa Aquarid
is easily recognized by its very slow velocity.

The Anthelion radiant is now centered at 00:12 (003) +02. This area of the
sky is located in southern Pisces, seven degrees southeast of the faint star
Omega Piscium. Since this radiant is large and diffuse, any slow to medium
speed meteor from southern Pisces, northwestern Cetus, or southern Pegasus
could be a candidate for this shower. The center of this area 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 no matter your
location. With an entry velocity of 30 km/sec., the average anthelion meteor
would be of medium-slow speed.

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. There
is also the possibility that some of this activity may be caused by the
"Jupiter family of comets", comets which have been altered by Jupiter's
gravity into much shorter orbits. 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 anthelions 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 send their reports to the International
Meteor Organization (IMO) should list these meteors as Southern Piscids
(SPI).

The September Perseids (SPR) peak on the morning of September 9 with an
average ZHR of six. The radiant is located at 04:04 (061) +47, which places
it in eastern Perseus, two degrees southwest of the fourth magnitude star Mu
Persei. Due to the extreme northern declination, this shower is only visible
from the southern tropics northward. The radiant is best placed in the sky
just before the start of morning twilight, when it lies highest above the
horizon. At 64km/sec., the average September Perseid is swift. This shower
is also known as the Epsilon Perseids and the Delta Aurigids. Those who
report to the IMO should label these meteors as "DAU".

The Sporadic rates for the Northern Hemisphere are now rising toward their
high plateau for the year. Observers can expect around ten random meteors
per hour during the morning hours as seen from locations in the Northern
hemisphere. During the dark evening hours perhaps two random meteors can be
seen per hour north of the equator. Sporadic rates seen from the Southern
Hemisphere are falling and will bottom out in October. From south of the
equator one would expect to see approximately six random meteors per hour
during the morning hours and one per hour during the evening. Evening rates
are reduced due to moonlight.

There are three more possible radiants that deserve your attention this
week. For the last decade or so around September 12th there has been
activity noted from the constellations of Triangulum, Aries, and Taurus. The
Triangulid radiant seems to produce the most activity. The activity centers
are located near the bright stars of Alpha Trianguli, Hamal (Alpha Arietis),
and between the Hyades and Pleiades star clusters in western Taurus. All
three radiants would produce meteors in the medium to swift velocity range.
These showers are also best seen during the last hour before the start of
morning twilight. Plotting and video observations would be most valuable for
studying these suspected radiants.

Kappa Aquarids (KAQ)    22:08 (332) -08
Hourly Rate = N. Hemisphere >1 - S. Hemisphere >1

Anthelion    00:12 (003) +02
Hourly Rate = N. Hemisphere 2 - S. Hemisphere 2

Sep. Perseids (SPR)   04:04 (061) +47
Hourly Rate = N. Hemisphere 3 - S. Hemisphere >1

Clear Skies!
Robert Lunsford
American Meteor Society