Meteor Activity Outlook for June 27-July 3, 2009

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.