(meteorobs) Meteor Activity Outlook for September 30-October 6, 2005

[Robert Lunsford]

The moon reaches its new phase on Monday October 3rd. At this time the moon
will rise and set with the sun and will not interfere at all with nighttime
observing. 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 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 October 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 01:36 (024) +10. This area of the
sky is located in eastern Pisces, three degrees northwest of the fourth
magnitude star Omicron Piscium. Since this radiant is large and diffuse, any
slow to medium speed meteor from eastern Pisces, northern Cetus, or
southwestern Aries 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) reach a ZHR of one early in the month from a position
located at 05:32 (083) +14. This position lies in northern Orion, four
degrees north of the fourth magnitude star Lambda Orionis. The radiant is
best placed in the sky just before the start of morning twilight, when it is
located near the meridian and lies highest above the horizon. With the
maximum not occurring until October 21, current rates would be low, most
likely less than one shower member per hour. At 66km/sec., the average
Orionid is swift and bright shower members tend to leave persistent trains.

The Delta Aurigids (DAU) peaked on the morning of September 23 with an
average ZHR of three. The radiant is located at 05:40 (085) +49, which
places it in northern Auriga, very close to the position occupied by the
faint star Omicron Aurigae. Due to the extreme northern declination, this
shower is only visible from the southern tropics northward. The radiant is
best placed in the sky just before the start of morning twilight, when it
lies highest above the horizon. Current rates would be low, most likely less
than one shower member per hour. At 64km/sec., the average Delta Aurigid is
swift. This shower is also known as the Epsilon Perseids and the September
Perseids.

The Sporadic rates for the Northern Hemisphere are now reaching 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 falling and will bottom out in October. From south of the
equator one would expect to see approximately eight random meteors per hour
during the morning hours and three per hour during the evening.

Anthelion    01:36 (024) +10
Hourly Rate = N. Hemisphere 2 - S. Hemisphere 2

Orionids (ORI)   05:32 (083) +14
Hourly Rate = N. Hemisphere >1 - S. Hemisphere >1

Delta Aurigids (DAU)   05:40 (085) +49
Hourly Rate = N. Hemisphere >1 - S. Hemisphere 0

Clear Skies!
Robert Lunsford
American Meteor Society