Meteor Activity Outlook for June 20-26, 2009

June is another slow month for meteor activity.
There are no major showers active in June and only the Antihelion source can be
counted on for continuous activity. Even the Antihelion is located so far south
this time of year that rates rarely exceed two per hour as seen from the northern
hemisphere. Sporadic rates reach their nadir in June 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 Monday June 22. At this time the moon lies near the sun and is invisible at
night. Later in the week the moon emerges from the solar glare as a waxing crescent
but will still set well before the more active morning hours arrive. The estimated total
hourly rates for evening observers this week is near three as seen from the northern
hemisphere and five for those situated south of the equator. For morning observers
the estimated total hourly rates should be near nine for those located in the
mid-northern hemisphere (45 N) and nineteen 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 June 20/21. 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:

Next week, a few June Bootids (JBO) may be seen during the evening hours
radiating from a position near 14:44 (221) +49. This area of the sky lies in
northern Bootes, ten degrees northwest 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. Maximum activity is expected on June 27th.
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 18:48 (282) -23. This
area of the sky lies in central Sagittarius, four degrees northwest of the second
magnitude star Nunki (Sigma 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
southeastern Ophiuchus, Scutum, Sagittarius, 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 northeastern Aquila this time of year. The radiant lies at 20:00
(300) -08, which is located three degrees northeast of the bright first
magnitude star Altair (Alpha Aquilae). 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 is
expected on June 25th. 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
seven 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 sixteen per hour as
seen from rural observing sites and four per hour during the evening hours. Locations
between these two extremes would see activity between the listed figures.

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.