(meteorobs) Meteor Activity Outlook for May 11-17, 2007

[Robert Lunsford]

May provides the peak of the Eta Aquarid meteor shower. This is the
strongest shower visible from the southern hemisphere but unfortunately this
year glare from the waning gibbous moon will obscure all but the brightest
meteors. The much weaker Eta Lyrids peak on May 9 under slightly better
conditions. Sporadic rates seen in the northern hemisphere are nearing the
nadir of their activity curve. The lowest rates are observed in June. On a
positive note, rates seen from the southern hemisphere are increasing toward
a July maximum.

During this period the moon reaches its new phase on Wednesday May 16. At
this time the moon will rise and set with the sun and will not interfere
with observing. This weekend the waning crescent moon will be present in the
late morning sky and will cause slight interference which can be easily
overcome by keeping the moon out of ones field of view. The estimated total
hourly rates for evening observers this week is near two for those north of
the equator and three for observers south of the equator. For morning
observers the estimated total hourly rates should be near nine for those
located in the northern hemisphere and seventeen for those viewing from
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.
Morning rates are slightly reduced all this week due to moonlight.

The radiant positions listed below are exact for Saturday night/Sunday
morning May 12/13. 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. Doing this 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 Antihelion (ANT) radiant is now centered at 16:20 (245) -22. This area
of the sky is centered in northwestern Scorpius, seven degrees northwest of
the orange first magnitude star Antares (Alpha Scorpii). This radiant is
best placed near 0200 local daylight time (LDT), when it lies on the
meridian and is highest in the sky. Rates at this time should be near one
per hour as seen in the northern hemisphere and two per hour for those
located south of the equator. With an entry velocity of 30 km/sec., the
average antihelion meteor would be of medium-slow speed.

The Eta Lyrids (ELY) are produced by comet IRAS-Araki-Alcock, which passed
very close to the Earth twenty four years ago this May. Weak activity from
this radiant has been seen in most years from May 5 through May 17, with
maximum activity occurring on May 9. The current radiant position is located
at 19:24 (291) +45. This area of the sky is located in western Cygnus, four
degrees west of the third magnitude star Delta Cygni. 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 44 kilometers per
second, a majority of these meteors will appear to move at moderate speeds.

The Eta Aquarids (ETA) are particles from Halley's Comet, which last passed
through the inner solar system in 1986. The Earth's orbit does not currently
pass through recent orbits of Halley's comet. Rather, the meteors we now see
as Eta Aquarids were produced by the comet many hundreds of years ago when
the orbit of the comet was located much closer to the Earth. The maximum of
the Eta Aquarids occurs on May 6. At that time rates can reach thirty shower
members per hour as seen from the northern tropical areas southward. Current
rates would vary from zero to five per hour depending on your latitude and
observing conditions. The radiant is located at 22:52 (343) +02. This area
of the sky is located at the intersection of the constellations Pegasus,
Aquarius and Pisces. 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 66 kilometers per second, a majority of these meteors
will appear to move swiftly.

Sporadic rates are slowing decreasing for observers in the northern
hemisphere and slightly rising for those south of the equator. One would
expect to see perhaps five random meteors during the last hour before dawn
from rural observing sites located in the northern hemisphere. During the
first dark hour after the end of evening twilight, perhaps two random
meteors can be seen per hour. Sporadic rates increase as the night
progresses so rates seen near midnight would be near three per hour. Late
morning sporadic rates seen from the southern hemisphere are now near twelve
per hour from rural observing sites. During the first dark hour after the
end of evening twilight, perhaps three random meteors can be seen per hour,
increasing to six by midnight. Morning rates are slightly reduced all this
week due to moonlight.

Antihelion (ANT) - 15:24 (231) -19
Northern Hemisphere - 1   Southern Hemisphere - 2

Eta Lyrids (ELY)  19:24 (291) +45
Northern Hemisphere - 1   Southern Hemisphere - <1

Eta Aquarids (ETA) 22:04 (331) -03
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#X2007

Clear Skies!
Robert Lunsford
American Meteor Society