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(meteorobs) Meteor Activity Outlook for September 14-20, 2001
Our personal interests seem a bit trivial today. I was thinking of
skipping this outlook altogether this week but was spurred on by Stephen
Kaplan's message urging us to "to return to our lives as quickly as
possible to show the terrorists that their efforts have achieved
ABSOLUTELY NOTHING." So here is my meager contribution to help us
continue observing. Let us not forget those innocent victims who lost
their lives yesterday and those most affected by their passing. May the
stars shine a bit brighter for them tonight.
The moon reaches its new phase on Monday September 17th. This will be
the best week to try to see meteor activity this month. 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 15 for the Northern Hemisphere and 7 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 15/16. The positions do not change
greatly day to day so these positions may be 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 near 1 per hour. The radiant is
located at 22:24 (336) -06 which lies in central Aquarius 3 degrees
northeast of the 4th magnitude star Theta Aquarii. Like all evening
activity these meteors are slow no matter where they are seen in the
sky. This would aid in their identification after midnight when the
swift meteors from the east begin to appear.
The Antihelion radiant is now located at 00:32 (008) +04. This area of
the sky is located in central Pisces 4 degrees southwest of the 4th
magnitude star Delta Piscium. Any slow to medium speed meteor from
Pisces or northwestern Cetus 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 reached maximum activity on Saturday September 8.
This is not a sharp maximum so rates should not be that much lower this
week. Expected rates would be 1-2 shower members per hour as seen from
the Northern Hemisphere. The radiant is located at 04:32 (068) +49 which
lies in eastern Perseus some 7 degrees northwest of the zero magnitude
star Capella (Alpha Aurigae). 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.
The Northern Apex radiant is now located at 05:32 (083) +38. This
position lies in central Auriga 4 degrees northwest of the 3rd magnitude
star Theta 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 Auriga could be a good candidate. As seen from the Northern
Hemisphere this source should produce at least 2-3 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 due to the low radiant
altitude seen south of the equator.
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 05:32 (083) +08. This position lies in northwestern Orion
3 degrees northeast 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 northern 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 7 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 4 random meteors being seen per hour during the
late morning hours and 1 per hour during the evening.
Robert Lunsford
AMS Visual Program Coordinator
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