(meteorobs) Meteor Activity Outlook for June 27-July 3, 2009

[Robert Lunsford]

After several months of low activity the meteor rates for both hemispheres
see a marked increase in July. In the northern hemisphere the change is not
noticeable until mid-month when several southern radiants, the Perseids, and
sporadic rates all increase in activity. Southern rates are good all month
long.

During this period the moon reaches its first quarter phase on Monday June
29. At this time the moon lies ninety degrees east of the sun and remains in
the sky until 0100 LDT (Local Daylight Time). As the week progresses the
window of dark skies between moonset and the start of morning twilight
shrinks. The estimated total hourly rates for evening observers this week is
near two 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 ten for those located in the mid-northern hemisphere (45 N)
and twenty 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. Evening rates are
reduced due to moonlight.

The radiant positions and rates listed below are exact for Saturday
night/Sunday morning June 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. 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:

A few June Bootids (JBO) may be seen during the evening hours radiating from
a position near 14:56 (224) +48. This area of the sky lies in northern
Bootes, seven degrees north of the fourth magnitude star Beta Bootis. This
radiant is best placed as soon as it becomes dark. Rates at this time should
be less than one for those located in the northern hemisphere and near zero
for observers south of the equator. With an entry velocity of 18 km/sec.,
the average June Bootid meteor would be of very slow speed.

The wide Antihelion (ANT) radiant is now centered at 19:16 (289) -21. This
area of the sky lies in central Sagittarius, close to the third magnitude
star Pi Sagittarii. 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
Aquila, Scutum, Sagittarius, western Capricornus, or southern Serpens Cauda
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.

Studies by Sirko Molau of the IMO's video data has revealed an active
radiant located in southeastern Aquila this time of year. The radiant lies
at 20:24 (306) -06, which lies in a blank region of the sky located between
Theta Aquilae and Alpha Capricorni. Note that this description was in error
last week. This radiant is best placed near 0300 LDT when it lies on the
meridian and is highest in the sky. Rates are most likely less than one per
hour regardless of your location. Maximum activity occurs on July 6th, not
June 25th as reported last week. With an entry velocity of 40 km/sec., the
average North June Aquilid (NZC) meteor would be of medium speed, but
noticeably more swift than the nearby Antihelion radiant.

As seen from the mid-northern hemisphere (45N) one would expect to see
approximately eight 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 seventeen 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. Evening rates are reduced by
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.

June Bootids (JBO) - 14:56 (224) +48   Velocity - 18km/sec.
Hourly Rates - Northern Hemisphere <1 - Southern Hemisphere - 0

Antihelion (ANT) - 19:16 (289) -21   Velocity - 30km/sec.
Hourly Rates - Northern Hemisphere 2 - Southern Hemisphere - 3

North June Aquilid (NZC) - 20:24 (306) -06   Velocity - 40km/sec.
Hourly Rates - Northern Hemisphere <1 - Southern Hemisphere - <1

*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