(meteorobs) Meteor Activity Outlook for December 31, 2004 - January 6, 2005

[Robert Lunsford]

This upcoming period will see the moon reaching its last quarter phase on
Monday January 3. At this time the moon will be rising near local midnight,
obscuring some of the faint meteor 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 twelve for
those located in the Northern Hemisphere and eight 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 January 1/2. 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 Anthelion radiant is now centered at 07:44 (116) +21. This area of the
sky is located in eastern Gemini, seven degrees south of the first magnitude
star Pollux (Beta Geminorum). Since this radiant is large and diffuse, any
slow to medium speed meteor from northern Canis Minor, eastern Gemini,
northwestern Monoceros or western Cancer 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. At this time expect
to see two 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. Observers who send their reports to the
International Meteor Organization (I.M.O.) should label these meteors as
Delta Cancrids (DCA).

The Gamma Velids (GVE) are the first of many weak southern showers active
during January and February. The Gamma Velids are listed among the radiants
of the Dutch Meteor Society and reach maximum activity on January 5. Current
rates would be low, most likely less than one shower member per hour. The
radiant is currently located near 08:16 (124) -47. This position lies in
western Vela, only one degree northeast of the second magnitude star Gamma
Velorum. The radiant lies highest in the sky between 0100 and 0200. This
shower is not visible north of latitude 45 north. At 35 km/sec. the Gamma
Velids produce meteors of average velocity.

The Coma Berenicids (COM) are active from a radiant located at 12:32 (188)
+19. This area of the sky lies in central Coma Berenices, close to the faint
star 24 Comae Berenices. This  radiant is best placed for viewing just
before dawn,  when it lies highest above the horizon. The predicted date of
maximum activity was December 19,  when the predicted ZHR reached five.
At 65 km/sec. the Coma Berenicids produce mostly swift meteors with the
brighter shower members leaving  persistent trains.

The Quadrantids (QUA) reach maximum activity on January 3 near 1220
Universal Time. This corresponds to 0720 EST and 0420 PST. Western North
America is the prime area in which to view this shower at its best this
year. The radiant is located at 15:20 (230) +49. This position lies in a
sparse area of northern Bootes, ten degrees south of the third magnitude
star Iota Draconis.  Rates can exceed one hundred shower members per hour
but with the moon spoiling the display for most areas, I would expect most
observers to see rates near fifty per hour at best. While some activity may
be seen during the evening hours from high northern latitude areas, the
prime hours lie in the late morning hours when the radiant rises high into
the northeastern sky. This shower is not well seen south of the equator as
the radiant does not rise sufficiently high into the sky before the start of
morning twilight. At 41 km/sec. the Quadrantids produce meteors of average
velocity with a few persistent trains.

The Sporadic rates for the Northern Hemisphere are now just past their
annual peak. One would expect to see perhaps six random meteors per hour
during the last hours before dawn from rural observing sites. During the
evening hours perhaps two random meteors can be seen per hour. Sporadic
rates seen from the Southern Hemisphere are increasing toward a peak this
month. One would see approximately six random meteors per hour during the
late morning hours and one per hour during the evening. Morning rates are
reduced due to moonlight.

Anthelion        Radiant Position  = 07:44  (116) +21
Hourly Rate = 2  N. Hemisphere, 1  S. Hemisphere

Gamma Velid (GVE)   Radiant Position  = 08:16 (124)  -47
Hourly Rate = 0  N. Hemisphere, 1  S. Hemisphere

Coma Berenicid (COM)   Radiant Position  = 12:32 (188)  +19
Hourly Rate = 1  N. Hemisphere, <1  S. Hemisphere

Quadrantid (QUA)   Radiant Position  = 15:20 (230)  +49
Hourly Rate = 2  N. Hemisphere, <1  S. Hemisphere

Clear Skies!
Robert Lunsford
American Meteor Society