(meteorobs) Meteor Activity Outlook for March 11-17, 2005

[Robert Lunsford]

This upcoming period will see the moon reaching its first quarter phase on
Thursday March 17.  At this time the moon will set near midnight, allowing
morning observers a dark sky in which to view the sparse activity. This
weekend will have a waxing crescent moon that will set early in the evening,
allowing an even better opportunity to view the March meteor activity. 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 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 March 12/13. 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 12:24 (186) -02. This area of the
sky is located in western Virgo, four degrees southwest of the third
magnitude star Porrima (Gamma Virginis). Since this radiant is large and
diffuse, any slow to medium speed meteor from northeastern Crater, Virgo or
Corvus 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 Gamma Normids (GNO) are active from a radiant located at 16:32
(248) -51. This position lies in eastern Norma, two degrees east of the
fourth magnitude star Gamma Normae. 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 Delta Pavonids (DPA) are listed among the radiants of the Dutch Meteor
Society. They are predicted to peak on March 29. The radiant currently lies
at 18:48 (282) -60. This area of the sky is located in a sparse area of
western Pavo, some twenty five degrees southwest of the second magnitude
star Peacock (Alpha Pavonis). This area of the sky is too far south to be
seen north of the northern equatorial areas. The rate at maximum is five
shower members per hour. These rates are rarely seen except from far
southern locations such as Australia, South Africa and southern South
America. Current hourly rates would be less than one. The best time to view
this activity is just before the start of morning twilight, when the radiant
lies highest in a dark sky. With an entry velocity of 60 kilometers per
second, a majority of these meteors will appear to move swiftly.

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.

Anthelion        Radiant Position  = 12:24  (186) -02
Hourly Rate = 2  N. Hemisphere, 2  S. Hemisphere

Gamma Normids (GNO)   Radiant Position  = 16:32 (248)  -51
Hourly Rate = 0  N. Hemisphere, 2  S. Hemisphere

Delta Pavonids (DPA)   Radiant Position  = 18:48 (282)  -60
Hourly Rate = 0  N. Hemisphere, <1  S. Hemisphere

Clear Skies!
Robert Lunsford
American Meteor Society