(meteorobs) Meteor Activity Outlook for April 1-7, 2005

[Robert Lunsford]

This upcoming period will see the moon reaching its last quarter phase on
Saturday April 2.  At this time the moon rise near midnight and will be in
the sky the remainder of the night. If your sky is transparent, successful
meteor observations can be obtained if you view with the moon out of your
field of view.  As the week progresses the moon becomes less of a nuisance
as it approaches its new phase. 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 five for those located in
the Northern Hemisphere and eight for those in the Southern Hemisphere.
Morning rates for all locations are reduced due to moonlight. 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 April 2/3. 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 13:48 (207) -10. This area of the
sky is located in central Virgo, four degrees east of the first magnitude
star Spica (Alpha Virginis). Since this radiant is large and diffuse, any
slow to medium speed meteor from Virgo or western Libra 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 Delta Pavonids (DPA) are listed among the radiants of the Dutch Meteor
Society. They were predicted to peak on March 29. The radiant currently lies
at 21:04 (316) -64. This area of the sky is located in eastern Pavo some
twenty five west of the fourth magnitude star Gamma 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 likely be 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. Moonlight will decrease this number down to three
per hour this week. During the dark 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 five random meteors per hour during the
late morning hours and three per hour during the evening.

Anthelion  (Virginids)     13:48  (207)  -10
Hourly Rate =     2   N. Hemisphere,    2  S. Hemisphere

Delta Pavonids (DPA)   21:04  (316)  -64
Hourly Rate =     0   N.  Hemisphere,   1  S. Hemisphere

Clear Skies!
Robert Lunsford
American Meteor Society