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(meteorobs) Meteor Activity Outlook for October 5-11, 2001
The moon reaches its last quarter phase on Tuesday October 9th. This
means on that day it will rise sometime near 1:00 AM for those still on
Daylight Savings Time or Summer Time. Morning observations will be
affected by moonlight while the evening will be nice and dark. The
estimated total hourly rates for evening observers this week should be
near 3 for those in the Northern Hemisphere and 1 for those in the
Southern Hemisphere. For morning observers the estimated total hourly
rates should be near 13 for the Northern Hemisphere and 6 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 October 6/7. The positions do not change greatly
day to day so these positions may be used during this entire period.
The Draconids or Giacobinids reach a sharp peak on October 8. Activity
is usually only present when the parent comet, 21P Giacobini-Zinner, is
near perihelion. This last occurred in 1998 and won't occur again until
2005. If any activity does occur it will sparse with a radiant located
at 17:28 (262) +54. This area of the sky is located in southern Draco
close to the 5th magnitude star Nu Draconis. This star is one of the 4
stars that make up the "Lozenge" of Draco. This area of the sky lies
high in the northwest after dusk for observers north of the equator. For
those viewing from south of the equator this part of the sky lies close
to the horizon and soon sets after the end of evening twilight. The moon
will not rise until after midnight allowing a window of several hours
for northern observers to view any potential activity. These meteors are
extremely slow no matter where they appear in the sky.
The Antihelion radiant is now located at 01:56 (029) +11. This area of
the sky is located in southwestern Aries 9 degrees south of the 3rd
magnitude star Sheratan (Beta Arietis). Any slow to medium speed meteor
from eastern Pisces, southwestern Aries, or northeastern 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 "North or South Taurids", depending if they appear
to radiate from north or south of the ecliptic.
The Orionids are in the early stages of their activity curve. The
maximum is not predicted to occur until October 21 so current rates
would be low, most likely less than 1 shower member per hour. The
radiant position lies at 05:44 (086) +14 which places it in extreme
northeastern Taurus, 6 degrees northwest of the 1st magnitude orange
star Betelgeuse (Alpha Orionis). With an entry velocity of 66 km/sec.
the Orionid meteors are swift when seen far from the radiant and high in
the sky. They will appear to move slower if seen close to the radiant or
near the horizon. The radiant lies due south at dawn and activity is
best seen during the hours just before the arrival of dawn when the
radiant lies highest in the sky.
The Delta Aurigids reach maximum activity on Wednesday October 10. Once
again this is not a sharp maximum so rates should much the same all this
week. Expected rates would be 1-2 shower members per hour as seen from
the Northern Hemisphere. The radiant is located at 06:04 (091) +49 which
lies in northeastern Auriga 5 degrees north of the 2nd magnitude star
Menkalinan (Beta 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.
The Northern Apex radiant is now located at 06:56 (104) +38. This
position lies in eastern Auriga 4 degrees northwest of the 4th magnitude
star Theta Geminorum. 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 Auriga or northwestern Gemini 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 06:56 (104) +08. This position lies in northeastern
Monoceros 5 degrees southeast of the 3rd magnitude star Xi Geminorum.
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
southern Gemini, northern Monoceros, or western Canis Minor 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 6 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 3 random meteors being seen per hour during the
late morning hours and 1 per hour during the evening. Sporadic rates are
reduced during the morning hours due to moonlight.
Clear Skies!
Robert Lunsford
AMS Visual Program Coordinator
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