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(meteorobs) Meteor Activity Outlook for April 13-19, 2001



The moon reaches its last quarter phase on Sunday April 15. The moon
will be a nuisance for those observing during the morning hours but the
evening hours will be free of interfering moonlight. The estimated total
hourly rates for evening observers this week should be near 2 for those
located in the Northern Hemisphere and 3 for those located in the
Southern Hemisphere.  For morning observers the estimated total hourly
rates would be near 5 for the Northern Hemisphere and 8 for those
located in the Southern Hemisphere. Morning rates are reduced due to
moonlight. These morning rates assume that you are watching from rural
areas away from sources of light pollution except for the moon. 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 positions listed below are exact for
Saturday night/Sunday morning April 14/15. The positions do not change
greatly day to day so these positions may be used during this entire
period.

For southern observers the Pi Puppids are now becoming active. This
diffuse radiant is currently located at 07:00 (105) -43. This area of
the sky is located in western Puppis between the 3rd magnitude stars Nu 
and Sigma Puppi. Puppis is located low in the southwestern sky after
sunset for those north of the equator and much higher in the western sky
for those located further south. Regardless of your location activity is 
best seen as soon as it becomes dark. At this early date activity from
this radiant is doubtful from any location. Even at maximum activity
(April 23) this radiant can be quiet. The Pi Puppids are most active 
when periodic comet Grigg-Skjellerup is near perihelion. This will next
occur in 2002. These meteors are extremely slow.

The Antihelion radiant is now located at 14:36 (219) -14. This area of
the sky is located in western Libra directly between the stars Lambda
Virginis and Zubenelgenubi (Alpha Librae). Any slow to medium speed 
meteor from Libra or southeastern Virgo 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 to 2 meteors per hour from this source.
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. It is easiest to
simply list these meteors as "ANT" but a majority of meteor
organizations prefer that you list them from the constellation in which
the radiant is currently located. For instance those who share reports
with the IMO should label these meteors as Virginids (VIR). 

Lyrid activity is just now beginning to occur. The current radiant
position lies at 17:32 (263) +34. This position lies in central Hercules
just east of the "Keystone". For observers in the Northern Hemisphere
this area of the sky rises near 2100 (9pm) local daylight time (2000
local standard time). For areas south of the equator it rises much
later. It is best seen from all locations near 0400 local daylight time
(0300 local standard time) when it lies high overhead for northern
observers and low in the south for southern observers. Since maximum
activity is still a week away (April 22) rates are expected to be less
than one shower member per hour. Lyrid meteors possess a medium entry
velocity of 49 km/sec. This will produce meteors that are slow if seen
close to the radiant or close to the horizon. Those seen far from the
radiant and high in the sky will travel at medium speeds. Lyrid meteors
are produced by the debris from comet Thatcher (1861 I). At maximum
activity Lyrid hourly rates are usually near 15 for those located in the 
Northern Hemisphere. Much less activity is seen from the Southern
Hemisphere. There have been surprising Lyrid displays throughout history
when rates have approached and exceeded 100 meteors per hour. This
year's maximum occurs on a weekend with the moon out of the way. Don't
miss this rare and favorable combination to view the Lyrids!

The Northern Apex radiant is now located at 19:36 (294) -06. This
position lies in southern Aquila near the faint star Kappa Aquilae. 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 southern
Aquila, Scutum, northeastern Sagittarius, or extreme northwestern
Capricornus could be a good candidate. As seen from the Northern 
Hemisphere this source should produce at least 1 meteor per hour during
the last few hours before dawn. Rates seen from the Southern Hemisphere
should be better with perhaps 2 of these meteors being seen 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 19:36 (294) -36. This position lies in a remote area of
southeastern Sagittarius. 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 Sagittarius, Corona Australis,
Microscopium, northern Telescopium, or northern Indus could possibly be
a candidate from this source. As seen from the Northern Hemisphere this
source now lies so low in the southeastern sky that chances are little
or no activity will be seen. With the radiant being situated much higher
in the sky, rates seen from the Southern Hemisphere should be better
with perhaps 2-3 of these meteors being seen per hour.

The Delta Pavonids is a far southern shower listed among the radiants of
the Dutch Meteor Society. It reached maximum activity on March 29 with a
predicted ZHR of 5. Current rates are most likely less than 1 per hour.
The radiant position lies at 22:20 (335) -66. This area of the sky is
located in western Tucana close to the faint star Delta Tucanae. I would
not expect any activity from this radiant to be visible north of 20
degrees north latitude. This radiant is better seen from a location far
south of the equator during the last hour before morning twilight. These
meteors have a geocentric velocity of 35 km/sec., which means they would
appear to move slowly if seen near the radiant or near the horizon. If
seen far from the radiant and high in the sky then they would travel
with medium speeds much like the Geminids of December.

The Sporadic rates for the Northern Hemisphere are now in decline and
will do so until June. One would expect to see perhaps 1-2 random
meteors per hour during the last hours before dawn from rural observing
sites with lunar interference. During the evening hours perhaps 1 random
meteor can be seen per hour. Rates seen from the Southern Hemisphere
would now be slightly better than those seen in the Northern Hemisphere
with perhaps 3 random meteors being seen per hour during the late
morning hours and 2 per hour during the evening.

Clear Skies!
Robert Lunsford
AMS Visual Program ordinator
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