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(meteorobs) Meteor Activity Outlook for Oct. 30-Nov. 6, 2003
The moon reaches its first quarter phase on Saturday November 1. At this
time the moon lies ninety degrees east of the sun and will set near midnight
local standard time. As the week progresses the moon will enter the morning
sky and will limit the meteor activity as it approaches its full phase. 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 twenty
for those located in the Northern Hemisphere and fourteen 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 November 1/2. 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.
On November 1, 2003, near 0930 Universal Time, the Earth will pass within
0.007 astronomical units from the orbit of rediscovered asteroid 1937 UB
Hermes. This particular time favors observers located in North and Central
America, where the radiant will be high in a dark sky. While chances for any
activity is remote, the skies should be monitored on that night for any
unusual activity. The radiant will be centered at 02:38 (039) +04, which is
located in northeastern Cetus, very close to the third magnitude star Gamma
Ceti. The radiant will be very large and will overlap the nearby Taurid
(antihelion) radiants. The possibility of Taurid meteors appearing as Cetids
will be quite high. On November 1, the center of the antihelion radiant will
be located five degrees southwest of the Pleiades star cluster. On this date
an average of five Taurid meteors are produced each hour. While the Taurid
meteors are slow, any activity from Hermes will be even slower.
The Antihelion radiant is now centered at 03:40 (055) +19. This area of the
sky is located in western Taurus, five degrees southwest of the famous naked
eye Pleiades open star cluster. Since this radiant is large and diffuse, any
slow to medium speed meteor from eastern Aries or western Taurus could be a
candidate for this shower. The center of this area is best placed near 0100
local standard time when it lies on the meridian and is highest in the sky.
We are now starting to see an increase in the antihelion activity as the
Earth encounters debris from comet 1P Encke in addition to the normal
material. At this time expect to see 5 shower members per hour from areas
north of the equator and 3 per hour for locations 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. Those who report to the IMO should list these meteors as Northern
Taurids (NTA) or Southern Taurids (STA) depending on whether the meteors
radiant from north or south of the ecliptic.
The Orionids (ORI) peaked on Tuesday morning October 21 with predicted ZHR's
of twenty. The radiant is currently located at 06:52 (103) +16, which places
it in southern Gemini, three degrees east of the second magnitude star
Alhena (Gamma Geminorum). The radiant is best placed near 0300 local
standard time, when it lies on the meridian and highest in the sky. Current
rates should be near 2 shower members per hour. 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 Zeta Puppids are listed among the radiants of the Dutch Meteor Society.
This shower peaks on November 13 with a ZHR of only 3. The radiant is
located at 07:16 (109) -40. This position lies in central Puppis, three
degrees south of the third magnitude star Pi Puppis. These meteors are best
seen near 0400 local standard time when the radiant lies highest above the
horizon in a dark sky. At 41 km/sec. the Zeta Puppids produce meteors of
average velocity.
The Northern Apex radiant is now centered at 08:40 (130) +33. This position
lies on the Lynx/Cancer border, fifteen degrees northeast of the first
magnitude star Pollux (Beta 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. Since this radiant is large and diffuse, any meteor from northern
Cancer or southern Lynx could be a candidate from this source. 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 08:40 (130) +03. This position lies in northwestern Hydra
very close to the fourth magnitude star Sigma Hydrae. Like the northern
apex, these meteors are best seen toward dawn when the radiant lies highest
above the horizon in a dark sky. Since this radiant is also large and
diffuse, any meteor from northwestern Hydra, southern Cancer or eastern
Canis Minor 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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