(meteorobs) Meteor Activity Outlook for August 31-September 6, 2007

[Robert Lunsford]

September offers longer nights and cooler temperatures in the northern
hemisphere. In the sky no major showers are visible from either hemisphere
but the northern hemisphere enjoys the advantage of higher sporadic rates.
The two recognized minor showers active in early September have high
northern declinations (celestial latitude) therefore are much better suited
to be viewed from locations north of the equator. Toward the end of the
month the antihelion radiant becomes entangled with the two Taurid radiants
and is impossible to seperate. Therefore the antihelion radiant will be
excluded from the list until the end of the Taurid activity period late in
November. Observers in the southern hemisphere suffer from some of their
lowest rates of the year this month. The Taurid radiants are not too badly
placed so observers south of the equator can expect to see a little of this
activity toward the end of the month.

During this period the moon reaches its last quarter phase on Tuesday
September 4. At this time the half illuminated moon is located ninety
degrees west of the sun and rises near 0100 local daylight time. The
estimated total hourly rates for evening observers this week is near four
for those located north of the equator and one for observers south of the
equator. For morning observers the estimated total hourly rates should be
near ten for those located in the northern hemisphere and five for those
viewing from south of the equator. 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 by moonlight.

The radiant positions and rates listed below are exact for Saturday
night/Sunday morning September 1/2. 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 study of the IMO's video database has led to the discovery of
an active radiant in Ursa Minor this week. The shower peaks on September 1
from a radiant located at 17:24 (261) +83. This position lies in the handle
of the Little Dipper just west of the fourth magnitude star Epsilon Ursae
Minoris. The radiant is best placed near 2000 (8pm) local daylight time,
when it lies highest in the sky. Current rates would mostly likely be less
than one per hour, but this is uncertain. With an entry velocity of
38km/sec., activity from this radiant would be of medium velocity.

The Antihelion (ANT) radiant is now centered at 23:28 (352) -02. This area
of the sky is located in a western Pisces, three degrees south of the faint
star Kappa Piscium. This radiant is best placed near 0200 LDT, when it lies
on the meridian and is highest in the sky. Rates at this time should be near
two per hour regardless of your location. With an entry velocity of 30
km/sec., the average antihelion meteor would be of medium-slow speed.

The Alpha Aurigids (AUR) are predicted to reach maximum activity at 11:37
Universal Time on September 1. This timing favors western North America and
the eastern pacific area including Hawaii. Other areas are expected to see
little from this radiant. The radiant position is usually located near 05:36
(084) +42, which is located in central Auriga, five degrees southeast of the
brilliant zero magnitude yellow star Capella (Alpha Aurigae). Near the time
of maximum the radiant may be slightly different from this position but the
swift meteors from Auriga will be easy to differenciate from other activity
that night. This radiant is circimpolar north of 48 degrees north latitude.
For areas further south in the northern hemisphere, the radiant rises during
the late evening hours. From south of the equator the radiant will rise
during the late morning hours (if at all) depending on your southern
latitude. Regardless of location the radiant is best placed during the last
dark hour before morning twilight. At 66 km/sec., these meteors are swift,
often exhibiting persistent trains. The moon will be a major factor on
September 1, obscuring the faint meteors. Finding dry, transparent skies and
facing away from the moon will be the best way overcome the lunar glare.

Sirko Molau's study of the IMO's video database has led to the discovery of
an active radiant in eastern Auriga this week. The shower peaks on September
1 from a radiant located at 07:24 (111) +39. This position lies six degrees
northwest of the second magnitude star Castor (Alpha Geminorum). The radiant
is best placed just before dawn when it lies highest in a dark sky. Current
rates would mostly likely be less than one per hour, but this is uncertain.
With an entry velocity of 39km/sec., most activity from this radiant would
be of medium velocities.

Sporadic rates are slowly rising for observers in the northern hemisphere
and falling steadily for those located south of the equator. One would
expect to see perhaps seven random meteors during the last hour before dawn
from rural observing sites in the northern hemisphere. During the first dark
hour after the end of evening twilight, perhaps four random meteors can be
seen per hour. As seen from the southern hemisphere late morning rates would
now be near three per hour. During the first dark hour after the end of
evening twilight, perhaps two random meteors can be seen per hour. Morning
rates are reduced by moonlight.

Sep. Ursae Minorids  17:24 (261) +83
Northern Hemisphere - 1>   Southern Hemisphere - 0

Antihelion (ANT) - 23:28 (352) -02 30 02:00 2 - 2 II
Northern Hemisphere - 2   Southern Hemisphere - 2

Alpha Aurigids (AUR)  05:36 (084) +42
Northern Hemisphere - 1   Southern Hemisphere - <1

66 AUR (66A)  07:24 (111) +39
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