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(meteorobs) Meteor Activity Outlook for September 7-13, 2001
The moon reaches its last quarter phase on Monday September 10th. The
evening sky will be totally free from interference from moonlight during
this entire period. The morning sky will be bathed in interfering
moonlight reducing rates seen after midnight. This is much the same
situation seen during last month's Perseid maximum when Perseid rates
were reduced by the morning moonlight. On the positive side, with each
passing day the moon becomes less illuminated and therefore less of a
problem. The estimated total hourly rates for evening observers this
week should be near 3 for those in the Northern Hemisphere and 2 for
those in the Southern Hemisphere. For morning observers the estimated
total hourly rates should be near 9 for the Northern Hemisphere and 4
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 for meteor activity. The morning
estimates are reduced due to moonlight. The positions listed below are
exact for Saturday night/Sunday morning September 8/9. The positions do
not change greatly day to day so these positions maybe used during this
entire period.
The Kappa Aquarids are listed among the radiants of the Dutch Meteor
Society. This is a weak shower that reaches maximum activity on
September 18. Current rates would be less than 1 per hour. The radiant
is located at 22:00 (330) -09 which lies in central Aquarius 8 degrees
south of the 3rd magnitude star Sadalmelik (Alpha Aquarii). This would
be a perfect time to try to see any of this activity as the radiant is
best placed on the meridian near midnight. Observers can watch for this
activity from 2100 (9pm) onward until moonrise, taking advantage of the
dark evening skies. Like all evening activity these meteors are slow no
matter where they are seen in the sky. This would also aid in their
identification after midnight when the swift meteors from the east
begin to appear.
The Antihelion radiant is now located at 00:04 (001) +01. This area of
the sky is located in western Pisces 7 degrees southeast of the 4th
magnitude star Omega Piscium. Any slow to medium speed meteor from the
eastern half Aquarius, northwestern Cetus, southeastern Pegasus, or
western Pisces may be a good candidate for this shower. This area of the
sky is best placed near 0200 local daylight time (0100 local standard
time) when it lies on the meridian. At this time expect to see perhaps 1
per hour from all locations. Unlike most of the annual showers the
antihelion radiant is produced by debris from unknown sources orbiting
in a direct motion like the earth. These sources are most likely
asteroids, which produce stony and metallic debris whose density is much
greater that produced by comets. This debris 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 radiant
is active all year from an area of the sky nearly opposite that of the
sun. The radiant will travel approximately one degree eastward per day
and travels through many different constellations over the course of a
year. Observers who share their reports with the International Meteor
Organization (I.M.O.) should label these meteors "Southern Piscids" or
SPI.
The September Perseids reach maximum activity on Saturday September 8.
This is not a sharp maximum and rates should not be that much lower
later in the week when the moon is less of a problem. The radiant is
located at 03:56 (059) +47 which lies in central Perseus 3 degrees east
of the 3rd magnitude star Delta Persei. This area of the sky lies close
to the zenith at dawn for observers in the mid Northern Hemisphere.
Shower activity is also visible from the south tropic latitudes but not
beyond 40 degrees south latitude. These meteors are swift when seen far
from the radiant and high in the sky. They will appear to move more
slowly if seen near the radiant or near the horizon. Do not confuse
these meteors with those similar appearing meteors from the northern
apex. Aiming your field of view to include both radiants would help with
shower association plus keep the moon out of your line of sight.
The Northern Apex radiant is now located at 05:04 (076) +38. This
position lies in west central Auriga 3 degrees south of the 3rd
magnitude star Eta Aurigae. This area of the sky is best placed for
viewing during the last dark hour before dawn. Since this radiant is
diffuse any meteors from eastern Perseus or Auriga could be a good
candidate. As seen from the Northern Hemisphere this source should
produce at least 2 meteors per hour during the last few hours before
dawn. Rates seen from the Southern Hemisphere would be much less at 0-1
per hour.
Like the antihelion radiant both apex radiants 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. There are meteors with a zero inclination that
radiate precisely from the apex point on the ecliptic, exactly 90
degrees west of the sun. These meteors are rare though as the earth
orbits the sun it "sweeps clean" much of the material that shares the
same orbit. Much more debris 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. Meteors from
both branches are normally included in the sporadic count but should
also be noted in some manner as to which branch of the apex complex they
appear to radiate.
The Southern Apex source lies exactly 30 degrees south of its northern
counterpart at 05:04 (076) +08. This position lies in northwestern Orion
5 degrees northwest of the 2th magnitude star Bellatrix (Gamma Orionis).
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
southeastern Taurus or western Orion could be a candidate from this
source. Rates should be close to 1 per hour from most locations.
The Sporadic rates for the Northern Hemisphere are now near 4 meteors
per hour during the last hours before dawn from rural observing sites.
This estimate and the morning estimate for the Southern Hemisphere does
not include the apex meteors listed above. During the evening hours
perhaps 3 random meteors can be seen per hour from the Northern
Hemisphere. Rates seen from the Southern Hemisphere are now near their
annual low with perhaps 2 random meteors being seen per hour during the
late morning hours and 1 per hour during the evening. Moonlight
interferes with morning viewing as seen from both hemispheres and the
estimates mentioned reflect this reduced activity.
Clear Skies!
Robert Lunsford
AMS Visual Program Coordinator
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