(meteorobs) Meteor Activity Outlook for May 27-June 2, 2005

[Robert Lunsford]

This upcoming period will see the moon reaching its last quarter phase on
Monday May 30. At this time the moon rises near 0100 local daylight time and
will interfere with observing the remainder of the night. Those observers
able to view under transparent skies may have success observing the showers
mentioned below under these conditions as long as the moon is kept out of
their field of view. 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 six for those located in the
Northern Hemisphere and nine for those in the Southern Hemisphere. Morning
rates 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 May 28/29. 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 Omega Scorpids (OSC) are listed among the radiants of the Dutch Meteor
Society. I once felt these meteors were part of the antihelion complex but
they now seem to be a separate source. The peak is listed as June 2 with a
ZHR of 5. Actual observed rates would be less unless one lives deep in the
Southern Hemisphere. The current radiant position is 15:40 (235) -20. This
area of the sky is located in eastern Libra, five degrees west of the third
magnitude double star Acrab (Beta Scorpii). The best time to view this
activity is near midnight, local daylight time, when the radiant lies on the
meridian and is positioned highest in the sky. With an entry velocity of 21
kilometers per second, these meteors will appear to move slowly.

The Anthelion radiant is now centered at 17:28 (262) -23. This area of the
sky is located in southern Ophiuchus, three degrees northeast of the third
magnitude star Theta Ophiuchi. Since this radiant is large and diffuse, any
slow to medium speed meteor from northwestern Sagittarius, southern
Ophiuchus or northern Scorpius 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 hour from the Southern Hemisphere and one from the
Northern.

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
Sagittarids (SAG).

The Arietids (DAR) are active from a radiant located approximately thirty
degrees west of the sun. The radiant rises just before the start of morning
twilight and any activity would be seen shooting upwards from the
northeastern horizon. These meteors are of medium velocity and usually last
several seconds as they skim the outer regions of the earth's atmosphere.
The current radiant position is located at 02:32 (038) +19 which is located
in central Aries some five degrees southeast of the second magnitude star
Hamal (Alpha Arietis). This shower peaks on June 7 with a ZHR of 60. Even
with such strong rates the unfavorable altitude at the time of daybreak
makes seeing this activity a difficult challenge. On the other hand, those
with radio meteor equipment can easily detect this activity as it is the
strongest annual radio meteor shower of the year.

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 dark evening hours perhaps two random
meteors can be seen per hour. Sporadic rates seen from the Southern
Hemisphere are slowly increasing toward a July maximum. From south of the
equator one would expect to see approximately six random meteors per hour
during the late morning hours and three per hour during the evening. Morning
rates are reduced due to moonlight.

Omega Scorpiids  (OSC)    15:40 (235) -20
Hourly Rate =     <1   N. Hemisphere,    1  S. Hemisphere

Anthelion  (Sagittarids)    16:32 (248) -23
Hourly Rate =     1   N. Hemisphere,    2  S. Hemisphere

Arietids (DAR)   02:32  (038)  +19
Hourly Rate =    1  N.  Hemisphere,   <1  S. Hemisphere

Clear Skies!
Robert Lunsford
American Meteor Society
http://www.amsmeteors.org/lunsford/