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(meteorobs) Meteor Activity Outlook for May 18-24, 2001



This will be the best week of the month to watch for meteor activity.
The moon will be new on Tuesday May 22 and will be totally out of the
way for both morning and evening observing. The estimated total hourly
rates for evening observers this week should be near 1 for those in
Northern Hemisphere and 2 for Southern Hemisphere observers. For morning
observers the estimated total hourly rates should be near 8 for the
Northern Hemisphere and 13 for those located in the Southern Hemisphere.
These rates assume that you are watching from rural areas away from all
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 May 19/20. The positions do not change greatly day
to day so these positions may be used during this entire period.

The Antihelion radiant is now located at 16:52 (253) -22. This area of
the sky is located in southern Ophiuchus just 5 degrees northeast of the
brilliant orange star Antares. For this reason the antihelion meteors of
May have often been referred to as the Alpha Scorpids. Any slow to
medium speed meteor from northern Scorpius or southern Ophiuchus 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
locations in the Northern Hemisphere and 2 meteors per hour from the
Southern Hemisphere. 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 or the constellation where the
shower reaches maximum activity. For instance those who share reports
with the IMO should now label these meteors as Sagittarids (SAG).

The Beta Corona Australids are listed among the radiants of the Dutch
Meteor Society. They reached maximum activity on May 16. The current
radiant position lies at 19:16 (289) -40. This position lies on the  
Corona Australis/Sagittarius border just 1 degree north of the 4th
magnitude star Alpha Sagittarii. Due to the low southern declination
this shower is limited to observers in the tropics and the Southern
Hemisphere. The radiant lies highest in the sky near 0430 local daylight
time. ZHR's for this shower are only 3 so don't expect to see much, if
any activity, from this radiant. This is especially true if you live
north of the equator. At 45 km/sec. members of this shower would be of
medium velocity unless seen near the radiant or the horizon. 

The Northern Apex radiant is now located at 21:52 (328) +03. This
position lies in southwestern Pegasus 3 degrees southwest of the 4th
magnitude star Nu Pegasi. This is fairly close to the Eta Aquarid
radiant which lies to the east. It could be difficult to separate these
two radiants especially if the meteor travels due west. Both radiants
produce meteors with similar characteristics. During this week the
Northern Apex radiant would be the stronger source of activity. 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 northern
Aquarius, Equuleus, or southwestern Pegasus 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 similar. 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 21:52 (328) -27. This position lies in northwestern
Pisces Austrinus. 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  Pisces Austrinus, Microscopium, southeastern
Capricornus, northwestern Grus, or southwestern Aquarius 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 Eta Aquarids reached maximum activity on May 5. Rates are now
declining but perhaps one shower member can still be seen during the
last hour before dawn. The radiant position lies at 23:20 (350) +05. 
This area of the sky is in the "Circlet" of Pisces very close to the 4th
magnitude star 7 Piscium. This shower is difficult to see north of 45
degrees north latitude as the radiant does not rise very high before the 
beginning of morning twilight. The north and south tropical areas as
well as Australia and Southern Africa enjoy the best view of this
shower. These meteors have a geocentric velocity of 66 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 appear to move swiftly. The Eta Aquarids also produce a high 
percentage of persistent trains.

The Sporadic rates for the Northern Hemisphere are now near their lowest
levels of the year. One would expect to see perhaps 5 random meteors per
hour during the last hours before dawn from rural observing sites.
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 6 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 Coordinator
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