(meteorobs) Meteor Activity Outlook for May 23-29, 2009

[Robert Lunsford]

May is a fairly slow month for meteor activity. The Eta Aquariids are very
active the first two weeks of the month then fade as the month progresses.
The only other showers active this month are the Eta Lyrids and the
Antihelion radiant. These will add only 1-2 meteors per hour to the total
count. Sporadic rates are low but steady as seen from the mid-northern
hemisphere (45 N). Sporadic rates seen from the mid-southern hemisphere
(45 S) continue to rise this month toward a maximum in July.

During this period the moon reaches its new phase on Sunday May 24. At this
time the moon lies close to the sun and is not visible at night. Later in
the period the waxing crescent moon will enter the evening sky but will set
long before the active morning hours arrive. The estimated total hourly
rates for evening observers this week is near three as seen from the
northern hemisphere and four for those situated south of the equator. For
morning observers the estimated total hourly rates should be near eight for
those located in the mid-northern hemisphere (45 N) and eighteen for those
viewing from the mid-southern hemisphere (45 S). Locations between these two
extremes would see activity between the listed figures. 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 and rates listed below are exact for Saturday
night/Sunday morning May 23/24. 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. It must be remembered that meteor
activity is rarely seen at the radiant position. Rather they shoot outwards
from the radiant so it is best to center your field of view so that the
radiant lies at the edge and not the center. Viewing there will allow you to
easily trace the path of each meteor back to the radiant (if it is a shower
member) or in another direction if it is a sporadic. 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 following shower is expected to be active this week:

The wide Antihelion (ANT) radiant is now centered at 17:00 (255) -23. This
area of the sky lies in southern Ophiuchus, ten degrees northeast of the
first magnitude orange star Antares (Alpha Scorpii). This radiant is best
placed near 0200 LDT when it is located on the meridian and lies highest in
the sky above the horizon. Due to the large size of this radiant, any meteor
radiating from southern Ophiuchus or northern Scorpius could be a candidate
for this shower. Rates at this time should be near three per hour as seen
from the southern hemisphere and two as seen from north of the equator. With
an entry velocity of 30km/sec., the average Antihelion meteor would be of
medium-slow speed.

As seen from the mid-northern hemisphere (45N) one would expect to see
approximately six Sporadic meteors per hour during the last hour before dawn
as seen from rural observing sites. Evening rates would be near two per
hour. As seen from the mid-southern hemisphere (45S), morning rates would be
near fifteen per hour as seen from rural observing sites and three per hour
during the evening hours. Locations between these two extremes would see
activity between the listed figures.

The list below presents a summary of the expected activity this week. Rates
and positions are exact for Saturday night/Sunday morning but may be used
all week.

Antihelion (ANT) - 17:00 (255) -23    Velocity - 30km/sec.
Hourly Rates - Northern Hemisphere 2 - Southern Hemisphere - 3

*For a detailed explanation on the different classes of meteor showers and
other astronomical terms, please visit:
http://www.amsmeteors.org/showers.html#X2009

Clear Skies!
Robert Lunsford
American Meteor Society