(meteorobs) Meteor Activity Outlook for September 2-8, 2005

[Robert Lunsford]

This upcoming period will see the moon reaching its new phase on Saturday
September 3. As the week progresses, the moon will enter the evening sky as
a waxing thin crescent. It will set during the evening hours allowing an
unimpaired view of the rich 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.

The radiant positions listed below are exact for Saturday night/Sunday
morning September 3/4. 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 Anthelion radiant is now centered at 23:44 (356) -02. This area of the
sky is located in western Pisces, four degrees south of the faint star
Lambda Piscium. Since this radiant is large and diffuse, any slow to medium
speed meteor from western Pisces, northwestern Cetus, southern Pegasus, or
eastern Aquarius 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. Current rates should be near two shower members per
hour. The radiant is located at 03:36 (054) +46, which places it in central
Perseus, only two degrees south of the 3rd magnitude star Delta 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 Alpha Aurigids (AUR) peaked on the morning of September 1, with fairly
low rates in 2005. The actual rates fluctuate greatly from one year to the
next. Current rates would most likely be less than one shower member per
hour. The radiant is located at 05:48 (087) +42, which places it in central
Auriga some three degrees southwest of the second magnitude star Menkalinan
(Beta Aurigae) . Due to the extreme northern declination, this shower is
only visible from the southern tropics northward. The radiant is best placed
just before the start of morning twilight, when it lies highest in the sky.
At 66km/sec., the average Alpha Aurigid is swift.

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 four 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 late morning hours and two per hour during the evening.

Anthelion    23:44 (356) -02
Hourly Rate = N. Hemisphere 2 - S. Hemisphere 2

Sep. Perseids (SPR)   03:36 (054) +46
Hourly Rate = N. Hemisphere 2 - S. Hemisphere >1

Alpha Aurigids (AUR)   05:48 (087) +42
Hourly Rate = N. Hemisphere >1 - S. Hemisphere 0

Clear Skies!
Robert Lunsford
American Meteor Society