(meteorobs) Meteor Activity Outlook for May 16-22, 2009

Robert Lunsford lunro.imo.usa at cox.net
Fri May 15 14:31:30 EDT 2009


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 it last quarter phase on Sunday May 17.
On this date the half illuminated moon will rise near 0100 local daylight
time (LDT)and will remain in the sky the during the remainder of the night.
Later in the period the waning crescent moon will rise later in the morning
offering more dark skies. The estimated total hourly rates for evening
observers this week is near one as seen from the northern hemisphere and two
for those situated south of the equator. For morning observers the estimated
total hourly rates should be near six for those located in the mid-northern
hemisphere (45 N) and fourteen 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.
Morning rates are reduced due to moonlight.

The radiant positions and rates listed below are exact for Saturday
night/Sunday morning May 16/17. 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 showers are expected to be active this week:

The wide Antihelion (ANT) radiant is now centered at 16:36 (249) -22. This
area of the sky lies in extreme southeastern Ophiuchus, five 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 two
per hour as seen from the southern hemisphere and only one as seen from
north of the equator. With an entry velocity of 30km/sec., the average
Antihelion meteor would be of medium-slow speed.

The Eta Aquariids (ETA) are now dwindling in numbers. 1-2 may be seen in the
hour before dawn from tropical locations. The radiant is currently located
at 23:08 (347) +04. This area of the sky is located in extreme western
Pisces, three degrees northwest of the fourth magnitude star Gamma Piscium.
The best time to view this activity is during the hour before the start of
morning twilight, when the radiant lies highest in a dark sky. With an entry
velocity of 68 kilometers per second, a majority of these meteors will
appear to move swiftly.

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

The table 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) - 16:36 (249) -22    Velocity - 30km/sec.
Hourly Rates - Northern Hemisphere 1 - Southern Hemisphere - 2

Eta Aquariids (ETA) - 23:08 (347) +04     Velocity - 68km/sec.
Hourly Rates - Northern Hemisphere 1 - Southern Hemisphere - 2

*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 




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