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(meteorobs) Meteor Activity Outlook for Oct. 3-9, 2003
The moon reaches its first quarter phase on Thursday October 2. At this time
the moon lies ninety degrees east of the sun and sets near 0100 local
daylight time. This weekend the moon will not pose any problems for early
morning observers. Later in the period though, the waxing gibbous moon will
begin intruding into the morning sky, obscuring the morning activity. The
estimated total hourly rates for evening observers this week should be near
two for those in the Northern Hemisphere and one in the Southern Hemisphere.
For morning observers the estimated total hourly rates should be near
eighteen for those located in the Northern Hemisphere and twelve 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 due to moonlight.
The radiant positions listed below are exact for Saturday night/Sunday
morning October 4/5. 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 Giacobinids or October Draconids (GIA) are predicted to peak on October
9 near 0400 Universal Time. This corresponds to the evening hours of October
8 for those located in the American longitudes. The radiant is located at
17:28 (262) +54, which places it in southern Draco, two degrees northwest of
the third magnitude star Rastaban (Beta Draconis). This star is one of the
four that form the prominent head of Draco, also known as the "Lozenge".
Expected rates are always a guess. The full moon will certainly put a damper
on any possible display, especially since these meteors tend to be faint.
Due to the extreme northern declination, this shower is only visible from
the southern tropics northward. The radiant is best placed just as it
becomes dark during the evening hours. At 20km/sec., the average Giacobinid
is extremely slow. There is also the chance for enhanced activity occurring
near 1900 UT on October 7. This would favor the areas of Western Europe and
northwestern Africa. This prediction was provided by Esko Lyytinen.
The Antihelion radiant is now located at 01:48 (027) +11. This area of the
sky is located on the Pisces/Aries border, two degrees north of the fourth
magnitude star Omicron Piscium. Any slow to medium speed meteor from
northern Cetus, southwestern Aries or eastern 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 two shower members 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 Northern
Taurids (NTA) or Southern Taurids (STA).
The Orionids (ORI) peak on October 21 with predicted ZHR's of twenty.
Current rates would be very low, most likely near one per hour. The radiant
is currently located at 05:36 (085) +14, which places it in northern Orion,
seven degrees northwest of the first magnitude star Betelgeuse (Alpha
Orionis). The radiant is best placed near 0400 local daylight time, when it
lies on the meridian and highest in the sky. At 66km/sec., the average
Orionid is swift. What makes this shower interesting is the fact it is
produced by the debris from Halley's Comet, now seventeen years past its
last trip to the inner solar system. Despite this fact the shower is not
affected by the position of the comet and produces fairly stable rates year
after year.
The Delta Aurigids (DAU) peak on October 10 with predicted ZHR's of two.
This radiant is currently located at 05:56 (089) +49, which places it in
northern Auriga, five degrees north of the second magnitude star Menkalinan
(Beta 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 Delta Aurigid is swift.
The Northern Apex radiant is now located at 06:48 (102) +38. This position
lies in eastern Auriga, ten degrees northwest of the second magnitude star
Castor (Alpha Geminorum). 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 06:48 (102) +08. This position lies in northern Monoceros
directly between the first magnitude star Betelgeuse (Alpha Orionis) and the
zero magnitude star Procyon (Alpha Canis Minoris). 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, western Canis Minor or southwestern Gemini 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 near their annual
peak. 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 two 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. Evening rates are reduced due to moonlight.
Clear Skies!
Robert Lunsford
AMS Operations Manager
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