(meteorobs) Meteor Activity Outlook for May 26-June 1, 2006

[Robert Lunsford]

During May the Antihelion radiant moves from eastern Libra, through northern
Scorpius and into southern Ophiuchus. These areas of the sky are south of
the celestial equator, favoring observers watching from south of the
equator. Northern observers still suffer with low sporadic rates, especially
during the evening hours. This situation will not improve until mid-July,
when sporadic rates dramatically rise for northern observers. The overall
meteor activity is much like April, possibly slightly better in the south
and slightly worse in the north. The most favorable time to view meteor
activity this month would be during the first week of the month, when the
Eta Aquarids are near maximum activity.

During this period the moon will reach its new phase on Saturday May 27. At
this time the moon will rise and set with the sun and will not casue any
interference. As the week progresses the waxing crescent moon enter the
evening sky but will set long before the more active morning hours arrive.
The estimated total hourly rates for evening observers this week is near two
for observers in the northern hemisphere and three for those south of the
equator. For morning observers the estimated total hourly rates should be
near seven for those in the northern hemisphere and ten for those south of
the equator. 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 27/28. 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.

The Tau Herculids (THE) are produced by comet 73P/Schwassmann-Wachmann ,
which is currently making headlines as it passes close to the Earth. This
shower was once included in many shower lists. As our understanding of the
shower dynamics increased with this shower it became apparent that this
shower is visible only on rare occasions when the Earth passes through the
trails of debris produce by this comet. Therefore the Tau Herculids have
been removed from most lists and are only rarely discussed. With the close
approach of 73P/Schwassmann-Wachmann to the Earth in 2006, there exists the
small possibility that some activity may be seen from this shower during the
next two weeks. The Earth passes closest to the largest fragment of this
comet near 20:00 Universal Time on May 31. This is not a particularly close
approach so very low numbers, if any at all, are expected to appear then, or
during the remainder of this encounter. Using the IMO's shower parameters
listed at: http://www.imo.net/files/data/vmdb/vmdbrad.txt, I have calculated
that the radiant for this shower will be located near 15:16 (229) +34 this
weekend. This area of the sky is located in eastern Bootes near the position
of the fourth magnitude star Delta Bootis. The actual radiant of shower
members may differ significantly due to the fragmentation of this comet and
the very slow entry velocity. The best time to view possible activity is
near midnight when the radiant lies highest in the sky. This shower is well
placed for viewing in the northern hemisphere as it passes through the
zenith for those located at 40N latitude. At extreme northern latitudes the
length of the night is shortened appreciably, limiting the time one can view
activity. As one progresses southward the length of night increases but the
radiant altitude decreases. South of the equator the radiant altitude
becomes a major factor, reducing the possibility of seeing any activity from
this source. The radiant does not rise above the horizon south of 50S
latitude. With an entry velocity of only 15 kilometers per second, these
meteors will appear to move slowly, helping to aid in their identification.
A great majority of these meteors will possess an angular velocity less than
5 degrees per second with the highest possible angular velocity certainly
being less than 10 degrees per second. Please report any positive sightings
to the AMS, the IMO News list, or Meteorobs as soon as possible after your
observation.

The Antihelion (ANT) radiant is now centered at 17:16 (259) -23. This area
of the sky is located in southeastern Ophiuchus, two degrees northwest of
the third magnitude star Theta Ophiuchi. This radiant is best placed near
0200 local daylight time when it lies on the meridian and is highest in the
sky. Rates at this time should be near two per hour for those north of the
equator and three per hour south of the equator. With an entry velocity of
30 km/sec., the average Antihelion meteor would be of medium-slow speed.

The Daytime 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 02:28 (037) +17, which is located
in central Aries seven degrees east 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 nearing their annual
minimum activity. One would expect to see perhaps five random meteors per
hour during the last hours before dawn from rural observing sites. During
the evening hours perhaps two random meteors can be seen per hour. Sporadic
rates seen from the southern hemisphere are now increasing toward a
secondary maximum in July. One would see approximately eight random meteors
per hour during the late morning hours and three per hour during the
evening.

Tau Herculids (THE) 15:16 (229) +34   North >1 - South 0

Antihelion (ANT) 17:16 (259) -23   North 2 - South 3

Daytime Arietids (DAR)  02:28 (037) +17   North >1 - South >1

*For a detailed explanation on the different classes of meteor showers and
other astronomical terms, please visit:
http://www.amsmeteors.org/showers.html#X2006

Clear Skies!
Robert Lunsford
American Meteor Society