(meteorobs) Meteor Activity Outlook for October 21-27, 2005

[Robert Lunsford]

The moon reaches its last quarter phase on Tuesday October 25th. At this
time the moon will rise near 0100 with interfering moonlight occurring
during the remainder of the morning. The estimated total hourly rates for
evening observers this week should be near four for Northern Hemisphere
observers and three for those located in the Southern Hemisphere. For
morning observers the estimated total hourly rates should be near sixteen
for Northern Hemisphere observers and eleven 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.
Morning rates are reduced due to moonlight.

The radiant positions listed below are exact for Saturday night/Sunday
morning October 22/23. 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 03:00 (045) +16. This area of the
sky is located in eastern Aries, three degrees west of the brilliant orange
planet Mars. Since this radiant is large and diffuse, any slow to medium
speed meteor from Aries, northeastern Cetus, or western Taurus could be a
candidate for this shower. The center of this area is best placed near 0200
local daylight time when it lies on the meridian and is highest in the sky.
At this time expect to see two shower members per no matter your location.
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 Southern (STA) or
Northern Taurids (NTA), depending on whether the meteors radiate from south
or north of the ecliptic.

The Orionids (ORI) reached maximum activity on October 21 but usually
produce good activity through the 25th. The current radiant position is
located at 06:24 (096) +16. This position lies on the Orion/Gemini border,
two degrees west of the second magnitude star Alhena (Gamma Geminorum). The
radiant is best placed near 0400 when it is located near the meridian and
lies highest above the horizon. At 66km/sec., the average Orionid is swift
and bright shower members tend to leave persistent trains.

The Epsilon Geminids (EGE) peaked on October 18 with a predicted ZHR of two.
Current rates would be less than one shower member per hour. This radiant is
currently located at 07:04 (106) +27, which places it in northern Gemini,
four degrees southwest the fourth magnitude star Tau Geminorum. The radiant
is best placed near 0500 when it lies highest in the sky. At 70km/sec., the
average Epsilon Geminid is swift with a high percentage of persistent
trains.

The Leo Minorids (LMI) are listed among the radiants of the Dutch Meteor
Society. This is a short lived shower, reaching ZHR's in excess of one for
only three days (October 23-25). Peak ZHR's are two shower members on the
morning of October 24. This radiant is located at 10:48 (162) +37, which
places it in northeastern Leo Minor, three degrees east of the fourth
magnitude star Beta Leo Minoris The radiant is best placed just before dawn
when it lies highest in a dark sky. At 61km/sec., the average Leo Minorid is
swift.

The Sporadic rates for the Northern Hemisphere are now reaching their high
plateau for the year. Observers can expect around eight 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 have reached a minimum and will slowly rise during the remainder
of the year. From south of the equator one would expect to see approximately
four random meteors per hour during the morning hours and two per hour
during the evening. Morning rates are reduced due to moonlight.

Anthelion    02:32 (038) +14
Hourly Rate = N. Hemisphere 3 - S. Hemisphere 2

Orionids (ORI)   06:24 (096) +16
Hourly Rate = N. Hemisphere 5 - S. Hemisphere 5

Epsilon Geminids (EGE)   07:04 (106) +27
Hourly Rate = N. Hemisphere >1 - S. Hemisphere 0

Leo Minorids (LMI)   10:48 (162) +37
Hourly Rate = N. Hemisphere >1 - S. Hemisphere 0

Clear Skies!
Robert Lunsford
American Meteor Society