(meteorobs) Meteor Activity Outlook for November 12-18, 2004

[Robert Lunsford]

This upcoming period will see the moon reaching its new phase on Friday
November 12. This weekend the waxing crescent moon will set shortly after
dusk. Since a great majority of the nights will be moon-free, this will be
the best week to view meteor activity during November. 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
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.

The radiant positions listed below are exact for Saturday night/Sunday
morning November 13/14 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 03:48 (057) -02. This position
lies in northern Eridanus some twenty five degrees south of the famous
Pleiades star cluster. 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 04:28 (067) +22. This area of the
sky is located in northtern Taurus, five degrees north of the first
magnitude star Aldebaran (Alpha Tauri). Since this radiant is large and
diffuse, any slow to medium speed meteor from eastern Aries, northern Orion,
southern Perseus, southwestern Auriga or 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 four shower members per hour from the Northern Hemisphere and two 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 Alpha Monocerotids (AMO) reach maximum activity on November 21 with
normally low rates. This shower has the strange distinction of producing
short but very strong outbursts in years ending in "5". We are only one year
away from the next outburst so activity this year may be better than
average, especially for North and South America. The radiant is currently
located at 07:28 (112) +02. This position lies in southwestern Canis Minor,
four degrees southwest of the zero magnitude star Procyon (Alpha Canis
Minoris). These meteors are best seen near 0300 local standard time when the
radiant lies highest above the horizon in a dark sky. At 65 km/sec. the
Alpha Monocerotids produce mostly swift meteors.

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 07:52 (118) -42. This position
lies in southeastern Puppis, three degrees southwest of the second magnitude
star Zeta 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 09:28 (142) +29. This position
lies in northwestern Leo, six degrees southeast 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 three per hour for observers north of
the equator and one per hour for those observers south of the equator.  Be
careful as the Leonid radiant lies less than ten degrees to the southeast.

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 09:28 (142) -01. This position lies in western Hydra, eight
degrees north of the second magnitude star Alphard (Alpha 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, Sextans or southwestern Leo
could be a candidate from this source. Rates would now be near two per hour
regardless of your location.

The Leonids (LEO) reach a ZHR of one near November 14. Rates will remain low
until the night of maximum activity (November 19). The radiant is currently
located at 10:00 (150) +23. This position lies in northwestern Leo, three
degrees west of the third magnitude star Zeta Leonis. The radiant lies
highest above the horizon in a dark sky just before the start of morning
twilight. At 71 km/sec. the Leonids produce mostly swift meteors with a high
percentage of persistent trains.

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
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 six
random meteors being seen during the late morning hours and two per hour
during the evening.

Delta Eridanids (DER)   Radiant Position  = 03:48  (057)  -02
Hourly Rate = <1  N. Hemisphere, <1  S. Hemisphere

Anthelion (STA/NTA)   Radiant Position  = 04:28  (067)  +22
Hourly Rate = 4  N. Hemisphere, 2  S. Hemisphere

Alpha Monocerotids (AMO)   Radiant Position  = 07:28  (112)  +02
Hourly Rate = <1  N. Hemisphere, <1  S. Hemisphere

Zeta Puppids (ZPU)   Radiant Position  = 07:52  (118)  -42
Hourly Rate = <1  N. Hemisphere, 1  S. Hemisphere

Northern Apex    Radiant Position  = 09:28  (142)  +29
Hourly Rate = 3  N. Hemisphere, 1  S. Hemisphere

Southern Apex   Radiant Position  = 09:28  (142)  -01
Hourly Rate = 2  N.  Hemisphere, 2 S. Hemisphere

Leonids (LEO)  Radiant Position  = 10:00  (150)  +23
Hourly Rate = <1  N. Hemisphere, <1  S. Hemisphere

Clear Skies!
Robert Lunsford
American Meteor Society