(meteorobs) Meteor Activity Outlook for December 2-8, 2005

[Robert Lunsford]

The moon reaches its first quarter phase on Thursday December 8th. At this
time the moon will set near midnight allowing morning observers a good
opportunity to view the early December activity. This weekend will even be
more favorable as the waxing crescent moon will set earlier providing a
longer window of opportunity to view activity under dark skies. The
estimated total hourly rates for evening observers this week should be near
three for Northern Hemisphere observers and two for those located in the
Southern Hemisphere. For morning observers the estimated total hourly rates
should be near eighteen for Northern Hemisphere observers and fifteen for
those located 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 December 3/4. 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 (PHO) are a periodic shower that rarely produces activity.
The only impressive display produced by this shower occurred in 1956 when
ZHR's were near 100. Activity is possible from this radiant from November
28-December 9. The maximum is predicted to occur on December 6. The radiant
is currently located at 01:04 (016) -54. This position lies in southern
Phoenix some five degrees northwest of the brilliant first magnitude star
Archernar (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 05:48 (087) +23. This area of the
sky is located in eastern Taurus, three degrees northeast of the third
magnitude star Zeta Tauri. Since this radiant is large and diffuse, any slow
to medium speed meteor from northern Orion, western Gemini, southern Auriga,
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. Rates should be near three per hour from
the Northern Hemisphere and two per hour for observers south of the equator.
With an entry velocity of 30 km/sec., the average anthelion meteor would be
of medium-slow speed.

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. Those who send their reports to the International
Meteor Organization (IMO) should list these meteors as Chi Orionids (XOR)
depending on whether the meteors radiate from south or north of the
ecliptic.

The Monocerotids (MON) are currently active from a radiant located at 06:20
(095) +08. This area of the sky is located in northeastern Orion, five
degrees east of the first 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. Don't confuse this shower with the short duration Alpha
Monocerotids, which were active last month.

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 (HYD) 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 at their high plateau
for the year. Observers can expect around twelve random meteors per hour
during the morning hours as seen from locations in the Northern hemisphere.
During the dark evening hours perhaps four random meteors can be seen per
hour north of the equator. Sporadic rates seen from the Southern Hemisphere
are slowly rising from an October minimum. From south of the equator one
would expect to see approximately eight random meteors per hour during the
morning hours and two per hour during the evening.

Phoenicids (PHO)   01:04 (016) -54
Hourly Rate = N. Hemisphere 0 - S. Hemisphere <1

Anthelion    05:48 (087) +23
Hourly Rate = N. Hemisphere 3 - S. Hemisphere 2

Monocerotids (MON)   05:52 (088) +08
Hourly Rate = N. Hemisphere 1 - S. Hemisphere 1

 Puppid-Velids (PUP) 08:08 (122) -45
 Hourly Rate = N. Hemisphere <1 - S. Hemisphere 3

 Sigma Hydrids (HYD)  08:08 (122) +03
 Hourly Rate = N. Hemisphere 1 - S. Hemisphere 1

Clear Skies!
Robert Lunsford
American Meteor Society