(meteorobs) Meteor Activity Outlook for June 7-13, 2008

Robert Lunsford lunro.imo.usa at cox.net
Fri Jun 6 10:25:12 EDT 2008


June is another slow month for meteor activity. There are no major showers
active in June and only the Antihelion 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 first quarter phase on Tuesday June
10th. At this time the moon will be located ninety degrees east of the sun
and will set near 0100 local daylight time (LDT). This still leaves the more
active morning hours free of interfering moonlight. As seen from the
mid-northern hemisphere (45 N) the estimated total hourly rates during the
evening observers would be only one. For morning observers the estimated
total hourly rates should be near nine. For those located in the
mid-southern hemisphere (45 S) morning rates would be near twenty and
evening rates near two. 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.
Moonlight reduces rates seen during the evening hours this week.

The radiant positions and rates listed below are exact for Saturday
night/Sunday morning June 7/8. 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 large Antihelion (ANT) radiant is now centered at 18:00 (270) -23. This
area of the sky lies in western Sagittarius, seven degrees northwest of the
third magnitude star Lambda Sagittarii. Actually any meteor from eastern
Scorpius, southeastern Ophiuchus, as well as western Sagittarius could be a
candidate for this shower. This radiant is best placed near 0200 LDT when it
lies on the meridian and is highest in the sky. Rates at this time should be
near two for northern observers and three for observers south of the
equator. With an entry velocity of 30 km/sec., the average Antihelion meteor
would be of medium-slow speed.

During late May and early June, an occasional long meteor may shoot upwards
from the northeastern horizon just before dawn. Most likely these are
members of the Daytime Arietid (DAR) meteor shower. The radiant lies
approximately thirty degrees west of the sun therefore only a trace of this
shower can ever be seen by the visual observer. Dawn becomes too bright
before the radiant can achieve sufficient altitude to provide a good
display.

If this shower were visible in a dark sky it would be among the strongest
displays of the year. This shower is the strongest daylight/radio shower of
the year. The current position of the radiant is 03:00 (045) +25. This
position lies in eastern Aries, five degrees northwest of the fourth
magnitude star delta Arietis. Shower members would be visible only during
the last hour before dawn with rates at or less than one per hour. With an
entry velocity of 37 km/sec., the average Daytime Arietid meteor would be of
medium speed.

As seen from the mid-northern hemisphere (45N) the Sporadic rates are near
their lowest rates of the year. One would expect to see approximately six
random meteors during the last hour before dawn from rural observing sites
and only one per hour during the evening hours. As seen from the
mid-southern hemisphere (45S) morning rates would be near fifteen per hour
as seen from rural observing sites and two per hour during the evening
hours. Moonlight interferes during the evening hours.

The table below presents a condensed version of the expected activity this
week. Rates and positions are exact for Saturday night/Sunday morning.

Antihelion (ANT) - 18:00 (270) -23   Velocity -  30km/sec.
Northern Hemisphere - 2   Southern Hemisphere - 3

Daytime Arietid (DAR)  03:00 (045) +25   Velocity - 37km/sec.
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#X2008

Clear Skies!
Robert Lunsford
American Meteor Society




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