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(meteorobs) Meteor Activity Outlook for Nov. 21-27, 2003

The moon reaches its new phase on Sunday November 23. At this time the
moon lies in the vicinity of the sun as seen from the Earth. It will rise
and set with the sun and will not be visible in the night sky. Later in this
period the waxing crescent moon will appear in the evening sky but will not
cause any interference to late evening or early morning observers. The
estimated total hourly rates for evening observers this week should be near
two for those in the Northern Hemisphere and one in the Southern Hemisphere.
For morning observers the estimated total hourly rates should be near
sixteen 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.

The radiant positions listed below are exact for Saturday night/Sunday
morning November 22/23. The radiants do not change greatly day to day so the
given positions may be used during this entire period. Most star atlases
(available at science stores and libraries) 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 location. 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 last rise later in the night. This list also
provides the order of ascending velocity for each radiant with those listed
first usually being much slower than those last on the list. Velocity should
not be the prime factor for shower association as all showers can produce
slow meteors. Slow meteors can be produced from normally swift showers, such
as the Leonids, when meteors appear near the radiant or close to the
horizon. The true velocity is only revealed in shower members seen far from
the radiant and high in the sky.

The Delta Eridanids are listed among the radiants of the Dutch Meteor
Society. This shower peaked on November 13 with an estimated ZHR of only
one. The radiant is located at 04:16 (064) 00. This position lies on the
Eridanis/Taurus border some twenty 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 Antihelion radiant is now centered at 05:04 (076) +23. This area of the
sky is located in eastern Taurus, seven degrees southwest of the second
magnitude star El Nath (Beta Tauri). Since this radiant is large and
diffuse, any slow to medium speed meteor from northeastern Orion, 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. We are now seeing an increase in the
antihelion activity as the Earth encounters debris from comet 1P Encke in
addition to the normal material. At this time expect to see 3 shower members
per hour from areas north of the equator and 2 per hour for locations 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. 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 antihelions 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 report to the IMO should list these meteors as Northern
Taurids (NTA) or Southern Taurids (STA) depending on whether the meteors
radiant from north or south of the ecliptic.

The Alpha Monocerotids reach maximum activity on November 22 with normally
low rates. This shower has the strange distinction of producing short but
very strong outbursts in years ending in "5". We are only two years away
from the next outburst so activity this year may be better than average. The
radiant is currently located at 07:52 (118) 00. This position lies in
southwestern Canis Minor, seven degrees southeast 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 in a dark sky.
At 65 km/sec. the Alpha Monocerotids produce mostly swift meteors.

The Zeta Puppids are also listed among the radiants of the Dutch Meteor
Society. This shower peaked on November 13 with an estimated ZHR of only
three. The radiant is located at 08:16 (124) -44. This position lies on the
Puppis/Vela border, four degrees north 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. At 41 km/sec. the Zeta
Puppids produce meteors of average velocity.

The Northern Apex radiant is now centered at 10:04 (151) +26. This position
lies in northwestern Leo, two degrees east of the fourth magnitude star Mu
Leonis.This area of the sky is best placed for viewing during the last dark
hour before dawn when it lies highest in the sky. Since this radiant is
large and diffuse, any meteor from northeastern Cancer, northwestern Leo or
southwestern Leo Minor could be a candidate from this source. This source
should provide at least two meteors per hour for those in the Northern
Hemisphere and less than one per hour for those in the Southern Hemisphere.
Be careful when determining shower association as the Leonid radiant lies
close by. Both radiants product swift, often trained meteors.

Like the antihelion area, both apex areas are active all year long and
travel approximately one degree eastward per day. Unlike the antihelion
debris, these particles orbit the sun in a retrograde motion opposite that
of the earth and are most likely produced by unknown comets. They strike the
earth after their closest approach to the sun. Since they are moving in
opposite directions these particles strike the earth at tremendous
velocities often creating bright meteors with persistent trains. These
particles strike the earth on the morning side of earth and are best seen
just before morning twilight while the sky is still perfectly dark. This is
not really a "shower" per se, but an artificial radiant created by the
Earth's motion through space. Meteors from both branches are normally
included in the sporadic count. I feel it is a worthy project to see if it
is possible to distinguish these meteors from the normal sporadic
background. On rare occasions there are meteors with a zero inclination that
radiate precisely from the apex point on the ecliptic, exactly 90 degrees
west of the sun. In simplistic terms, these meteors are seldom seen since
the Earth "sweeps clean" much of the material that shares the same orbit as
our planet. Much more material is located just north and south of the
earth's orbit with slightly higher or lower inclinations. This creates the
northern and southern branches of the apex activity.

The Southern Apex source lies exactly 30 degrees south of its northern
counterpart at 10:04 (151) -04. This position lies in western Sextans some
ten degrees northeast of the second magnitude star Alphard (Alpha Hydrae).
Like the northern apex, these meteors are best seen toward dawn when the
radiant lies highest above the horizon in a dark sky. Since this radiant is
also large and diffuse, any meteor from western Hydra, southwestern Leo or
western Sextrans could be a candidate from this source. Rates would be now
close to two per hour regardless of your location.

The Leonids are winding down and will fall below rates of one per hour this
weekend. The radiant is located at 10:20 (155) +20. This position lies in
northwestern Leo very close to the second magnitude star Algeiba (Gamma
Leonis). The radiant lies highest above the horizon in a dark sky just
before the start of morning twilight. At 71 km/sec. the Leonids produce
mostly swift meteors with a high percentage of persistent trains.

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. This estimate and the
estimate for the Southern Hemisphere does not include meteors from the apex
radiants. During the evening hours perhaps three random meteors can be seen
per hour. Rates seen from the Southern Hemisphere would be approximately six
random meteors being seen per hour during the late morning hours and two
during the evening hours.

Clear Skies!
Robert Lunsford
AMS Operations Manager

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