(meteorobs) Meteor Activity Outlook for December 3-9, 2004

[Robert Lunsford]

This upcoming period will see the moon reaching its last quarter phase on
Sunday December 5. This weekend the waning moon will rise near midnight and
will obscure the fainter meteors that occur during the morning hours.
Successful observations can be carried out if your sky is transparent and
you keep the bright moon out of your field of view. The estimated total
hourly rates for evening observers this week should be near three 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
thirteen 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.
Morning rates are reduced due to moonlight.

The radiant positions listed below are exact for Saturday night/Sunday
morning December 4/5. 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 Phoenicids is a periodic shower that rarely produces activity. The only
impressive display produced by this shower occurred in 1956 when ZHR's were
near 100. On the night of possible maximum activity the moon will not rise
until after midnight, allowing several hours of dark sky viewing during the
late evening hours. The radiant is located at 01:12 (018) -53. This position
lies in southeastern Phoenix some 5 degrees northwest of the bright zero
magnitude star Achernar (Alpha Eridani). These meteors are best seen near
2100 (9pm) local standard time when the radiant lies highest above the
horizon in a dark sky. Due to the southerly declination, this shower is not
visible north of the Northern Tropical areas. The deep Southern Hemisphere
has the best chance of seeing any activity. At 22 km/sec. the Phoenicids
produce very slow meteors.

The Anthelion radiant is now centered at 05:52 (088) +23. This area of the
sky is located in extreme eastern Taurus, fifteen degrees north of the first
magnitude star Betelgeuse (Alpha Orionis). Since this radiant is large and
diffuse, any slow to medium speed meteor from northern Orion, southeastern
Auriga, western Gemini or eastern 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. 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. IMO observers should label these meteors as the
Chi Orionids (XOR).

The Monocerotids are currently active from a radiant located at 06:24 (096)
+08. This area of the sky is located in northwestern Monoceros, six degrees
west of the 1st magnitude star Betelgeuse (Alpha Orionis). These meteors are
best seen near 0100 local standard time when the radiant lies highest above
the horizon.  The peak for the Monocerotids occurs on December 8 when the
ZHR reaches 3. This shower would be equally well seen from both hemispheres.
At 42 km/sec. the Monocerotids produce meteors of average velocity.

The Geminids reach a ZHR of one on December 7. Rates will rise steadily as
we approach the December 13 maximum. The current radiant is located at 06:52
(103) +34. This area of the sky is located in northwestern Gemini, very
close to the 4th magnitude star Theta Geminorum. These meteors are best seen
near 0200 local standard time when the radiant lies highest above the
horizon. This shower is best suited for the Northern Hemisphere but some
activity can be see south of the equator when the radiant culminates low in
the northern sky. At 35 km/sec. the Geminids produce meteors of average
velocity.

The Puppid-Velids (PUP) is a vast complex of weak radiants similar to the
Virginid showers of March and April. Visual plots and photographic studies
have revealed many radiants in this area during November and December. The
DMS's Zeta Puppid radiant of November is no doubt part of this complex. The
combined strength of these radiants can produce a ZHR of ten. Actual hourly
rates will be much less unless you happen to be observing from the deep
Southern Hemisphere. The center of this activity is currently located at
08:08 (122) -45. This position lies in western Vela, three degrees north of
the second magnitude star Gamma Velorum. These meteors are best seen near
0300 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 Sigma Hydrids are currently active from a radiant located at 08:08 (122)
+03. This area of the sky is located in eastern Canis Minor, seven degrees
west 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.  The predicted peak for the Sigma Hydrids occurs on
December 12 when the ZHR reaches two. Recent studies have indicated that
this shower may peak earlier in the month so careful monitoring this week of
any activity would be valuable. Current rates would be near one shower
member per hour. At 58 km/sec. the Sigma Hydrids produce meteors of average
to swift velocity.

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. 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. Morning rates for both
hemispheres are reduced due to moonlight.

Phoenicids (PHO)   Radiant Position  = 01:12  (018)  -53
Hourly Rate = 0  N. Hemisphere, Var.  S. Hemisphere

Anthelion (XOR)   Radiant Position  = 05:52  (088)  +23
Hourly Rate = 2  N. Hemisphere, 1  S. Hemisphere

Monocerotids (MON)   Radiant Position  = 06:24  (096)  +08
Hourly Rate = 1  N. Hemisphere, 1  S. Hemisphere

Geminds (GEM)   Radiant Position  = 06:52  (103)  +34
Hourly Rate = <1  N. Hemisphere, <1  S. Hemisphere

Puppid-Velid (PUP)   Radiant Position  = 08:08  (122)  -45
Hourly Rate = 1  N. Hemisphere, 3  S. Hemisphere

Sigma Hydrid (HYD)   Radiant Position  = 08:08 (122)  +03
Hourly Rate = 1  N. Hemisphere, 1  S. Hemisphere

Clear Skies!
Robert Lunsford
American Meteor Society