(meteorobs) Meteor Activity Outlook for November 5-11, 2004

[Robert Lunsford]

This upcoming period will see the moon reaching its last quarter phase on
Friday November 5. This weekend the waning crescent moon will rise during
the early morning hours reducing the number of meteors to be seen.
Successful observations can be undertaken if one takes care to keep the moon
out of their field of view. The estimated total hourly rates for evening
observers this week should be near five for those in the Northern Hemisphere
and two for those observers south of the equator. For morning observers the
estimated total hourly rates should be near ten for those located in the
Northern Hemisphere and six for those in the Southern Hemisphere. Morning
rates are reduced due to moonlight. 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 November 6/7. These positions do not change greatly day to day so
the listed coordinates may be used during this entire period. Most star
atlases (available at science stores and planetariums) 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 latitude. 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 further down the list rise later in
the night.

These are the showers that may be observed this week:

The Delta Eridanids (ERI) are listed among the radiants of the Dutch Meteor
Society. This shower peaks on November 12 with an estimated ZHR of only one.
With such low rates it is difficult to differentiate these meteors from the
sporadic background. Suspected shower members must have the correct velocity
versus radiant distance. This basically means that true shower members move
slowly when seen near the radiant and only slightly faster when seen further
away.  The radiant is currently located at 03:20 (050) -01. This position
lies in northern Eridanus close to the point where the boundaries of
Eridanus, Cetus and Taurus meet. These meteors are best seen near 0000
(midnight) local standard time when the radiant lies highest above the
horizon. At 31 km/sec. the Delta Eridanids produce meteors of average and
slow velocities.

The Anthelion radiant is now centered at 04:00 (060) +20. This area of the
sky is located in western Taurus, five degrees southeast of the Pleiades, a
well-known naked eye open star. Since this radiant is large and diffuse, any
slow to medium speed meteor from eastern Aries, northeastern Cetus, southern
Perseus, southwestern Auriga 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 seeing 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 three shower members per hour from the Northern Hemisphere and one per
hour 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. There
is also the possibility that some of this activity may be caused by the
"Jupiter family of comets", comets which have been altered by Jupiter's
gravity into much shorter orbits. 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 anthelions 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. IMO observers should label these meteors as either
"Northern or Southern Taurids" (NTA or STA), depending on if the radiant
seems to be north or south of the ecliptic.

The Zeta Puppids (ZPU) are also listed among the radiants of the Dutch
Meteor Society. This shower peaks on November 13 with an estimated ZHR of
three. The radiant is currently located at 07:32 (113) -41. This position
lies in central Puppis, three degrees south of the third magnitude star
Sigma Puppis. These meteors are best seen near 0400 local standard time when
the radiant lies highest above the horizon in a dark sky. Observers located
in the Southern Hemisphere have an advantage viewing this shower as the
radiant will rise higher into their sky allowing more activity to be seen.
At 41 km/sec. the Zeta Puppids produce meteors of average velocity.

The Northern Apex radiant is now centered at 09:00 (135) +31. This position
lies in northern Cancer, four degrees southwest of the third magnitude star
Alpha Lyncis. 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, western Leo
Minor, northwestern Leo or southeastern Lynx could be a candidate from this
source. Rates would be now close to two per hour for observers north of the
equator and less than one per hour for those observers south of the equator.

Like the anthelion area, both apex areas are active all year long and travel
approximately one degree eastward per day. Unlike the anthelion 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 09:00 (135) +01. This position lies in western Hydra, five
degrees south of the third magnitude star Zeta 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 southern Cancer, eastern Canis Minor or
southwestern Leo could be a candidate from this source. Rates would now be
near one 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 five random meteors per hour during
the last hours before dawn from rural observing sites. This estimate and the
morning estimate for the Southern Hemisphere do not include the apex meteors
listed above. During the evening hours perhaps three random meteors can be
seen per hour from the Northern Hemisphere. Rates seen from the Southern
Hemisphere are now lower than those seen in the north with perhaps three
random meteors being seen during the late morning hours and two per hour
during the evening. Morning rates are reduced due to moonlight.

Delta Eridanids (DER)   Radiant Position  = 03:20  (050)  -01
Hourly Rate = <1  N. Hemisphere, <1  S. Hemisphere

Anthelion (STA/NTA)   Radiant Position  = 04:00  (060)  +20
Hourly Rate = 2  N. Hemisphere, 1  S. Hemisphere

The Zeta Puppids (ZPU)   Radiant Position  = 07:32  (113)  -41
Hourly Rate = 0  N. Hemisphere, 1  S. Hemisphere

Northern Apex    Radiant Position  = 09:00  (135)  +31
Hourly Rate = 2  N. Hemisphere, 0  S. Hemisphere

Southern Apex   Radiant Position  = 09:00  (135)  +01
Hourly Rate = 1  N.  Hemisphere, 1 S. Hemisphere

Clear Skies!
Robert Lunsford
American Meteor Society