(meteorobs) Meteor Activity Outlook for November 19-25, 2004

[Robert Lunsford]

This upcoming period will see the moon reaching its first quarter phase on
Friday November 19. This weekend the waxing gibbous moon will set shortly
after midnight leaving the remainder of the morning in excellent condition
to view the activity. The estimated total hourly rates for evening observers
this week should be near two for those in the Northern Hemisphere and one
for those observers south of the equator. For morning observers the
estimated total hourly rates should be near twenty-four for those located in
the Northern Hemisphere and twenty 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 20/21 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 peaked 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 04:12 (063) 00. This
position lies in southern Taurus some eighteen degrees southwest of the
first magnitude star Aldebaran (Alpha Tauri). 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 04:56 (074) +23. This area of the
sky is located in northern Taurus, seven degrees northwest of the first
magnitude star Aldebaran (Alpha Tauri). Since this radiant is large and
diffuse, any slow to medium speed meteor from northern Orion, southeastern
Perseus, southwestern Auriga or northern 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 of one or two shower members per hour. 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 as the maximum is predicted to occur near 08:45 Universal Time
(3:45am EST). I would still be surprised if the hourly rate exceeds five
this year. The radiant is currently located at 07:48 (117) +01. This
position lies in southeastern Canis Minor, five degrees southeast 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 peaked on November 13 with an estimated ZHR of
three. The radiant is currently located at 08:12 (123) -43. This position
lies in southeastern Puppis, three degrees southeast 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 09:56 (149) +27. This position
lies in northwestern Leo, very close to the fourth magnitude star Mu Leonis.
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 eastern 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 09:56 (149) -03. This position lies in western Sextans, eight
degrees northeast 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 southeastern Cancer, Sextans, western
Hydra 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) are expected to peak in activity on November 19. The best
time to see Leonid activity this year would be near 21:30 Universal Time,
when the Earth passes closest to the train of material left behind by comet
55P Temple-Tuttle in 1733. This time favors Asia as the radiant will not
have yet risen for Europe and Africa and it will be daylight in North and
South America. Expected rates could approach sixty per hour for a short
time. Other areas should see 10-15 Leonids per hour at best. The radiant is
currently located at 10:12 (153) +21. This position lies in northwestern
Leo, two degrees northwest of the second magnitude double star Algeiba
(Gamma 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 two 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 one per hour
during the evening. Evening rates for both hemispheres are reduced due to
moonlight.

Delta Eridanids (DER)   Radiant Position  = 04:12  (063)   00
Hourly Rate = <1  N. Hemisphere, <1  S. Hemisphere

Anthelion (STA/NTA)   Radiant Position  = 04:56  (074)  +23
Hourly Rate = 3  N. Hemisphere, 2  S. Hemisphere

Alpha Monocerotids (AMO)   Radiant Position  = 07:48  (117)  +01
Hourly Rate = <5  N. Hemisphere, <5  S. Hemisphere

Zeta Puppids (ZPU)   Radiant Position  = 08:12  (123)  -43
Hourly Rate = <1  N. Hemisphere, 1  S. Hemisphere

Northern Apex    Radiant Position  = 09:56  (149)  +27
Hourly Rate = 3  N. Hemisphere, 1  S. Hemisphere

Southern Apex   Radiant Position  = 09:56  (149)  -03
Hourly Rate = 2  N.  Hemisphere, 2 S. Hemisphere

Leonids (LEO)  Radiant Position  = 10:12  (153)  +21
Hourly Rate = 3 N. Hemisphere, 3  S. Hemisphere

Clear Skies!
Robert Lunsford
American Meteor Society