(meteorobs) Meteor Activity Outlook for March 4-10, 2005

[Robert Lunsford]

This upcoming period will see the moon reaching its new phase on Thursday
March 10.  At this time the moon will rise and set with the sun and will not
interfere with observing. This weekend will have a waning crescent moon
present in the morning sky that should not interfere too much with
observing. The estimated total hourly rates for evening observers this week
should be near two for those in the Northern Hemisphere and three for those
observers south of the equator. For morning observers the estimated total
hourly rates should be near seven for those located in the Northern
Hemisphere and ten 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 March 5/6. 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 Delta Leonids (DLE) peaked on February 25 with a ZHR of two. Current
rates would be less than one per hour. The radiant is located at 11:44 (176)
+13. This area of the sky is located in eastern Leo, three degrees southwest
of the second magnitude star Debebola (Beta Leonis). This position is close
to the antihelion source so care must be taken to separate the two. It is
quite possible that this radiant is a northern branch of the antihelion
source, active this time of year. The best time to view this activity is
near 0100 local time, when the radiant lies on the meridian and at its
highest point in the sky. With an entry velocity of 23 kilometers per
second, these meteors will appear to move slowly.

The Anthelion radiant is now centered at 11:56 (179) 00. This area of the
sky is located in western Virgo, three degrees southeast of the fourth
magnitude star Beta Virginis. Since this radiant is large and diffuse, any
slow to medium speed meteor from northern Crater, western Virgo or
southeastern Leo 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. At this time expect to see two shower
members per hour no matter your location.

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. Observers who send their reports to the
International Meteor Organization (I.M.O.) should label these meteors as
Virginids (VIR).

The Theta Centaurids (TCE) are almost over now for 2005. The date of maximum
activity was February 14 with a predicted ZHR of four. The radiant lies at
15:28 (232) -49. This position is on the Lupus/Norma border close to the
faint star Mu Lupi. This shower is not well seen north of the northern
tropical regions. It is possible to see activity from the latitude of San
Diego, CA as I have witnessed several of these meteors during my winter
observations. This area of the sky is best placed near 0500 local standard
time when it lies highest in the sky. At 60 km/sec. the Theta Centaurids
produce meteors of swift velocity.

The Gamma Normids (GNO) are active from a radiant located at 16:00
(240) -51. This position lies in central Norma, six degrees west of the
fourth magnitude star Gamma Normae. This is fairly close to the Theta
Centaurid radiant so care must be taken to separate the two. Average ZHR's
are near six at maximum (March 13). Due to the far southern declination of
the radiant, this shower is not well seen north of the northern equatorial
regions. This area of the sky is best placed near 0600 local standard time
when it lies highest in the sky. At 56 km/sec. the Gamma Normids normally
produce meteors of swift angular velocities.

The Sporadic rates for the Northern Hemisphere are now reaching their low
plateau for the year. From now through June morning sporadic rates will
remain near five per hour. During the evening hours perhaps two random
meteors can be seen per hour. Sporadic rates seen from the Southern
Hemisphere are slowing increasing toward a July maximum. From south of the
equator one would expect to see approximately eight random meteors per hour
during the late morning hours and three per hour during the evening.

Delta Leonids (DLE)   Radiant Position  = 11:44 (176)  +13
Hourly Rate = <1  N. Hemisphere, <1  S. Hemisphere

Anthelion        Radiant Position  = 11:56  (179) 00
Hourly Rate = 2  N. Hemisphere, 2  S. Hemisphere

Theta Centaurids (TCE)   Radiant Position  = 15:28 (232)  -49
Hourly Rate = 0  N. Hemisphere, <1  S. Hemisphere

Gamma Normids (GNO)   Radiant Position  = 16:00 (240)  -51
Hourly Rate = 0  N. Hemisphere, <1  S. Hemisphere

Clear Skies!
Robert Lunsford
American Meteor Society