(meteorobs) Meteor Activity Outlook for November 25-December 1, 2005

Robert Lunsford lunro.imo.usa at cox.net
Fri Nov 25 23:34:47 EST 2005


The moon reaches its new phase on Thursday December 1st. At this time the
moon will rise and set with the sun and will not hamper meteor observing any
time of the night. This weekend the waning crescent moon will rise during
the late morning hours and will not be too bothersome as long as it lies
outside your field of view. 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 fourteen for Northern
Hemisphere observers and ten 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 November 26/27. 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 00:48 (012) -51. This position lies in southern
Phoenix some ten degrees southeast of the second magnitude star Ankaa (Alpha
Phoenicis). 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 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 04:36 (069) +01. This
position lies in southeastern Taurus some twelve degrees northwest of the
zero magnitude star Rigel (Beta Orionis). 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 05:20 (080) +23. This area of the
sky is located in eastern Taurus, five degrees south of the second magnitude
star El Nath (Beta 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 05:52
(088) +08. This area of the sky is located in northeastern Orion, very close
to 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.

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 08:28 (127) -45. This position
lies in western Vela, five degrees northeast of the second magnitude star
Gamma Velorum. 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 Sporadic rates for the Northern Hemisphere are now at their high plateau
for the year. Observers can expect around ten random meteors per hour during
the morning hours as seen from locations in the Northern hemisphere. During
the dark evening hours perhaps three 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 six random meteors per hour during the morning
hours and two per hour during the evening.

Phoenicids (PHO)   00:48 (012) -51
Hourly Rate = N. Hemisphere 0 - S. Hemisphere <1

Delta Eridanids (ERI)   04:36 (069) +01
Hourly Rate = N. Hemisphere <1 - S. Hemisphere <1

Anthelion    05:20 (080) +23
Hourly Rate = N. Hemisphere 3 - S. Hemisphere 2

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

Zeta Puppids (ZPU)   08:28 (127) -45
Hourly Rate = N. Hemisphere <1 - S. Hemisphere 1

Clear Skies!
Robert Lunsford
American Meteor Society



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