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(meteorobs) Meteor Activity Outlook for Aug 1-7, 2003

The moon reaches its first quarter phase on Tuesday August 5. At this time
the moon will lie ninety degrees east of the sun and will set near 0100.
This will still allow uncompromised viewing during the most productive
morning hours. The estimated total hourly rates for evening observers this
week should be near two regardless of you latitude. For morning observers
the estimated total hourly rates should be near twenty five for those
located in the Northern Hemisphere and twenty for those 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 meteor activity. Evening
rates are reduced slightly due to moonlight.

The radiant positions listed below are exact for Saturday night/Sunday
morning Aug 2/3. The positions do not change greatly day to day so they may
be used during this entire period. Most star atlases (available at science
stores and libraries) will provide maps with grid lines of the celestial
coordinates so that you may find out exactly where these positions are
located in the sky. A planisphere or computer planetarium program is also
useful in showing the sky at any time of night on any date of the year.
Activity from each radiant is best seen when it is positioned highest in the
sky, either due north or south along the meridian, depending on your
location. Meteor activity is not seen from radiants that are located below
the horizon. The positions below are listed in a west to east manner in
order of right ascension (celestial longitude). The positions listed first
are located further west therefore are accessible earlier in the night while
those listed last rise later in the night. This list also provides the order
of ascending velocity for each radiant with those listed first usually being
much slower than those last on the list. Velocity should not be the prime
factor for shower association as all showers can produce slow meteors. Slow
meteors can be produced from normally swift showers, such as the Leonids,
when meteors appear near the radiant or close to the horizon. The true
velocity is only revealed in shower members seen far from the radiant and
high in the sky.

The Kappa Cygnids are now coming to life from a radiant is located at 18:48
(282) +58. This position is located in southern Draco some five degrees
northwest of the fourth magnitude star Kappa Cygni. This shower will not
reach maximum activity until the 18th so current rates will be much less
than one shower member per hour. The radiant is best placed near 2300 (11pm)
local daylight time when it lies on the meridian and highest in the sky. Due
to the extreme northern declination (celestial latitude) the Kappa Cygnids
are not well seen south of the equator. The velocity of the Kappa Cygnids is
25 km/sec., which is slower than your average meteor. This shower is rich in
bright meteors.

The Alpha Capricornid radiant is located at 20:44 (311) -09. This position
is located in extreme western Aquarius, only one degree northwest of the
fourth magnitude star Epsilon Aquarii. The broad maximum occurred on July 30
with a ZHR of four. The velocity of the Alpha Caps is 25 km/sec., which is
slower than your average meteor. The radiant is best placed near 0100 local
daylight time when it lies on the meridian. Like the Kappa Cygnids, the
Alpha Caps are known for their brightly colored fireballs.

The Antihelion radiant is now located at 21:40 (325) -13. This area of the
sky is located in eastern Capricornus only two degrees northwest of the
third magnitude star Nashira (Delta Capricorni). Any slow to medium speed
meteor from the eastern half of Capricornus or western Aquarius could be a
candidate for this shower. The radiant is best placed near 0200 local
daylight time when it lies on the meridian and is highest in the sky. At
this time expect to see two shower members per hour from locations north of
the equator and three an hour from areas south of the equator.

Unlike most of the annual showers the antihelion source is produced by
debris from unknown objects orbiting in a direct motion like the earth.
These objects are most likely asteroids, which produce stony and metallic
debris whose density is much greater than material produced by comets. This
material 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 source is active all year from an area of the sky nearly
opposite that of the sun. The center of this source will move approximately
one degree eastward per day and travels through many different
constellations over the course of a year. It may make sense to list these
meteors as antihelions or "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.

The South Iota Aquarids peak on August 4 with a ZHR of two. With these low
rates one would be lucky to see one shower member per hour. The radiant is
currently located at 22:08 (332) -15. This area of the sky is located in
southeastern Aquarius, very close to the fourth magnitude star Iota Aquarii.
This position is also very close to the antihelion radiant and without
plotting and velocity estimates, it would be impossible to separate meteors
from the two sources. At 34 km/sec. the SIA's have virtually the same
velocity as the antihelion meteors. This radiant is most active near 0200
LDT when it lies highest in the sky.

The North Delta Aquarids are currently active from a radiant located at
22:00 (330) -06. This area of the sky is located in central Aquarius, six
degrees south of the third magnitude star Sadalmelik (Alpha Aquarii). At 42
km/sec. the NDA's are a bit faster than your average meteor. This radiant is
most active near 0200 LDT when it lies highest in the sky. Like many of the
radiants active this time of year the NDA's are better seen from areas south
of the northern tropics or 30 degrees north latitude. Maximum hourly rates,
seen from the southern tropics, are currently two per hour.

The South Delta Aquarids are currently active from a radiant located at
22:52 (343) -14. This area of the sky is located in southern Aquarius, very
close to the fourth magnitude star Tau2 Aquarii. The radiant lies low in the
southeastern sky during the late evening hours and is not well seen until it
approaches the meridian near 0300 LDT. This shower peaked on July 28 so
current rates would be near 5 per hour as seen from favored southern
locations. These meteors encounter the earth at a speed of 41 km/sec. which
is a bit faster than average. These meteors are also better seen from the
Southern Hemisphere where the radiant passes high overhead.

The Pisces Austrinids are currently active from a radiant located at 23:04
(346) -27. This area of the sky lies in eastern Pisces Austrinus, only three
degrees northeast of the first magnitude star Fomalhaut (Alpha Piscis
Austrini). This shower peaked on the July 28 with ZHR's of five. Current
rates would only be 1-2 per hour as seen from the most favored southern
latitudes, where the radiant rises much higher in the sky. These meteors are
best seen near 0300 LDT, when the radiant lies highest above the horizon.
These meteors are of average velocity, slower than the Aquarids but faster
than the Alpha Caps and the antihelion meteors.

Perseid activity is now strengthening with each passing night. The current
radiant position lies at 02:20 (035) +57, which is located in northwestern
Perseus, and marked by the "Double Cluster" (h and x Persei) on most star
charts. The radiant is well placed for those in the Northern Hemisphere
during the last few hours before dawn. Due to the high northern declination
(celestial latitude) of the radiant, rates seen from the Southern Hemisphere
are very low or non-existent. Current Perseid rates for those north of the
equator should be near five per hour. These rates will gradually increase as
we approach the August 13 maximum. At 59 km/sec., Perseid meteors are swift,
often exhibiting persistent trains.

The Northern Apex radiant is now located at 02:40 (040) +30. This position
lies in northern Aries, very close to the faint star 39 Arietis. 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 Aries, southwestern
Perseus or southeastern Triangulum could be a good candidate for this
shower. This source should provide at least three meteors per hour for those
in the Northern Hemisphere and less than 1 per hour for those in the
Southern Hemisphere. Those viewing meteor activity in the southern skies
must be careful not to call these meteors Perseids as they appear quite
"Perseid-like", swift with numerous trains.

Like the antihelion area, both apex areas 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. This is
not really a "shower" per se, but an artificial radiant created by the
Earth's motion through space. Meteors from both branches are normally
included in the sporadic count. I feel it is a worthy project to see if it
is possible to distinguish these meteors from the normal sporadic
background. On rare occasions there are meteors with a zero inclination that
radiate precisely from the apex point on the ecliptic, exactly 90 degrees
west of the sun. In simplistic terms, these meteors are seldom seen since
the Earth "sweeps clean" much of the material that shares the same orbit as
our planet. Much more material 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.

The Southern Apex source lies exactly 30 degrees south of its northern
counterpart at 02:40 (040) 00. This position lies in north-central Cetus,
less than a degree north of the fourth magnitude star Delta Ceti. 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 north-central
Cetus, northwestern Eridanus, southern Aries or southwestern Pisces could be
a candidate from this source. Rates would be now close to two per hour
regardless of your location.

The Sporadic rates for the Northern Hemisphere are now rising slowly toward
their peak, which occurs during the last quarter of the year. One would
expect to see perhaps seven random meteors per hour during the last hours
before dawn from rural observing sites. This estimate and the estimate for
the Southern Hemisphere does not include meteors from the apex radiants.
During the evening hours perhaps two random meteors can be seen per hour.
Rates seen from the Southern Hemisphere would also be approximately seven
random meteors being seen per hour during the late morning hours and two
during the evening hours. Evening rates are reduced slightly for both
hemispheres due to moonlight.

Clear Skies!
Robert Lunsford
AMS Operations Manager

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