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(meteorobs) Meteor Activity Outlook for Sep 26-Oct. 2, 2003
The moon reaches its new phase on Friday September 26. At this time the
moon lies in the vicinity of the sun as seen from the Earth. This weekend
and beyond the waxing crescent moon will set early in the evening allowing
late night observers to view without interference. The estimated total
hourly rates for evening observers this week should be near three for those
in the Northern Hemisphere and two in the Southern Hemisphere. For morning
observers the estimated total hourly rates should be near sixteen for those
located in the Northern Hemisphere and ten 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.
The radiant positions listed below are exact for Saturday night/Sunday
morning September 27/28. The radiants do not change greatly day to day so
the given positions 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 Aquarids (KAQ) peaked on the morning of September 19 with
predicted ZHR's of three. The radiant is currently located at 23:04
(346) -01, which places it in western Pisces some four degrees south of the
fifth magnitude star Beta Piscium. This weekend I would expect rates less
than one shower member per hour. The radiant is best placed between the
hours of 2300 (11pm) and midnight, when it lies highest in the sky. At
19km/sec., the average Kappa Aquarid is very slow.
The Antihelion radiant is now located at 01:20 (020) +08. This area of the
sky is located in southeastern Pisces, two degrees northeast of the fifth
magnitude star Zeta Piscium. Any slow to medium speed meteor from the,
northern Cetus or southern Pisces 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 one shower
member per hour no matter your location.
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. Those who report to the IMO should list these meteors as Piscids
(SPI)
The September Perseids (DAU) peaked on the morning of September 9 with
predicted ZHR's of six. The radiant is currently located at 05:24 (081) +49,
which places it in northwestern Auriga, three degrees north of the zero
magnitude star Capella (Alpha Aurigae). This weekend I would expect rates of
one shower member per hour. Due to the extreme northern declination, this
shower is only visible from the southern tropics northward. The radiant is
best placed just before the start of morning twilight, when it lies highest
in the sky. At 64km/sec., the average September Perseid is swift.
The Northern Apex radiant is now located at 06:20 (095) +38. This position
lies in eastern Auriga, five degrees northeast of the third magnitude star
Theta Aurigae. This area of the sky is best placed for viewing during the
last dark hour before dawn when it lies highest in the sky. This source
should provide at least three meteors per hour for those in the Northern
Hemisphere and less than one per hour for those in the Southern Hemisphere.
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 06:20 (095) +08. This position lies on the Orion/Monoceros
border, five degrees east of the first magnitude star Betelgeuse (Alpha
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 western Monoceros, northeastern Orion or southeastern Taurus 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 eight 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 three random meteors can be seen per hour.
Rates seen from the Southern Hemisphere would be approximately six random
meteors being seen per hour during the late morning hours and one during the
evening hours.
Clear Skies!
Robert Lunsford
AMS Operations Manager
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