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(meteorobs) Meteor Activity Outlook for June 8-14, 2001
The moon is now a waning gibbous phase and will reach last quarter on
Wednesday June 13. While these conditions are more favorable than last
week the bright moonlight will still be a major factor for morning
observers. The estimated total hourly rates for evening observers this
week should be near 2 for those in Northern Hemisphere and 3 for
Southern Hemisphere observers. For morning observers there will be some
lunar interference so the estimated total hourly rates should be near 6
for the Northern Hemisphere and 9 for those located in the Southern
Hemisphere. These rates assume that you are watching from rural areas
away from all sources of light pollution except for the moon. The actual
rates will also depend on factors such as personal light and motion
perception, local weather conditions, alertness and experience in
watching for meteor activity. The positions listed below are exact for
Saturday night/Sunday morning June 9/10. The positions do not change
greatly day to day so these positions may be used during this entire
period.
The Antihelion radiant is now located at 18:12 (273) -23. This area of
the sky is located in northwestern Sagittarius 3 degrees northwest of
the the 3rd magnitude star Lambda Sagittarii. Any slow to medium speed
meteor from southern Serpens Cauda, northern Sagittarius, Southern
Scutum, or southeastern Ophiuchus may be a good candidate for this
shower. This area of the sky is best placed near 0200 local daylight
time (0100 local standard time) when it lies on the meridian. At this
time expect to see perhaps 1 per hour from locations in the Northern
Hemisphere and 2 meteors per hour from the Southern Hemisphere. Unlike
most of the annual showers the antihelion radiant is produced by debris
from unknown sources orbiting in a direct motion like the earth. These
sources are most likely asteroids, which produce stony and metallic
debris whose density is much greater that produced by comets. This
debris collides with the earth on the inbound portion of its orbit,
before its closest approach to the sun. Therefore we best see them just
after midnight when we are facing the direction from which this activity
appears. The antihelion radiant is active all year from an area of the
sky nearly opposite that of the sun. The radiant will travel
approximately one degree eastward per day and travels through many
different constellations over the course of a year. It is easiest to
simply list these meteors as "ANT" but a majority of meteor
organizations prefer that you list them from the constellation in which
the radiant is currently located or the constellation where the shower
reaches maximum activity. For instance those who share reports with the
IMO should now label these meteors as Sagittarids (SAG).
The June Lyrids/Xi Draconids reach maximum activity in mid June. While
recent June Lyrid activity has been strong enough to place it back on
the IMO's working list, some of this activity can be attributed to
another radiant exactly 20 degrees north of the June Lyrids. After its
initial discovery back in 1966 the June Lyrids produced some modest
activity for the next several years. During the early 70's reports of
this activity waned as did interest in this shower. Then after more than
two decades of poor activity two teams of observers in the USA and the
Netherlands discovered a sharp radiant active near Draco's head between
June 11 and the 17th in 1996. These meteors were much more numerous than
the June Lyrids that year and have continued to provide more activity
than its southern neighbor ever since. The current radiant positions
for the June Lyrids is 18:12 (273) +35 and 18:12 (273) +55 for the Xi
Draconids. These positions lie on the Lyra/Hercules border just 1 degree
southwest of the 4th magnitude star Kappa Lyrae and 3 degrees southeast
of 4th magnitude Xi Draconis, the northernmost star in the head of
Draco. As seen from the Northern Hemisphere these radiants lie high in
the sky passing high overhead during the short nights this time of year.
They are best placed between 0100 and 0200 when they lie highest above
the horizon. With moonlight present during the late evening and the
entire morning observers are urged to face toward the northern half of
the sky to keep the intense moonlight out of their field of view. While
some activity may be seen early in the week better results may be
obtained toward the weekend of June 16/17 when the moon becomes much
less of a factor. Meteors from both radiants are somewhat swift unless
seen near the radiant or low in the sky. Please keep a watch for this
activity and let us know which radiant produces the most activity for
you.
The Northern Apex radiant is now located at 23:12 (348) +11. This
position lies in southern Pegasus 4 degrees southeast of the 3rd
magnitude star Mirfak (Alpha Pegasi). This area of the sky is best
placed for viewing during the last dark hour before dawn. Since this
radiant is diffuse any meteors from western Pisces or southern Pegasus
could be a good candidate. As seen from the Northern Hemisphere this
source should produce at least 1 meteor per hour during the last few
hours before dawn. Rates seen from the Southern Hemisphere should be
similar. Like the antihelion radiant both apex radiants are active all
year long and travel approximately one degree eastward per day. Unlike
the antihelion debris these particles orbit the sun in a retrograde
motion opposite that of the earth and are most likely produced by
unknown comets. They strike the earth after their closest approach to
the sun. Since they are moving in opposite directions these particles
strike the earth at tremendous velocities often creating bright meteors
with persistent trains. These particles strike the earth on the morning
side of earth and are best seen just before morning twilight while
the sky is still perfectly dark. There are meteors with a zero
inclination that radiate precisely from the apex point on the ecliptic,
exactly 90 degrees west of the sun. These meteors are rare though as the
earth orbits the sun it "sweeps clean" much of the material that shares
the same orbit. Much more debris is located just north and south of the
earth's orbit with slightly higher or lower inclinations. This creates
the northern and southern branches of the apex activity. Meteors from
both branches are normally included in the sporadic count but should
also be noted in some manner as to which branch of the apex complex they
appear to radiate.
The Southern Apex source lies exactly 30 degrees south of its northern
counterpart at 23:12 (348) -19. This position lies in southern Aquarius
some 5 degrees southeast of the the 3rd magnitude (Delta Aquarii).
Like the northern apex these meteors are best seen toward dawn when the
radiant lies highest above the horizon in a dark sky. Any meteor from
northeastern Pisces Austrinus, eastern Capricornus, northwestern
Sculptor, or southern Aquarius could possibly be a candidate from this
source. As seen from the Northern Hemisphere this source now lies so low
in the southeastern sky that chances are little or no activity will be
seen. With the radiant being situated much higher in the sky, rates seen
from the Southern Hemisphere should be better with perhaps 2-3 of these
meteors being seen per hour.
The Daylight Arietids reached maximum activity on June 7. Unfortunately
this radiant lies only 30 degrees west of the sun and cannot be well
seen visually. This radiant is one of the strongest in the sky and
would produce a meteor a minute at maximum activity if it could be seen
high in the sky during dark hours. Unfortunately this is not the case
and these meteors remain elusive visually. Rates are well below 1 per
hour visually, even at maximum. To try to see one of these meteors face
away from the moon toward the northeast and look for medium speed
meteors moving up from the northeast horizon during the last half hour
before morning twilight. The radiant lies at 03:04 (046) +25 which is in
eastern Aries some 10 degrees west of the Pleiades star cluster.
The Sporadic rates for the Northern Hemisphere are now at their lowest
levels of the year. One would expect to see perhaps 3 random meteors per
hour during the last hours before dawn from rural observing sites. This
estimate and the morning estimate for the Southern Hemisphere does not
include the apex meteors listed above. During the evening hours perhaps
1 random meteor can be seen per hour from the Northern Hemisphere. Rates
seen from the Southern Hemisphere would now be slightly better than
those seen in the Northern with perhaps 4 random meteors being seen per
hour during the late morning hours and 2 per hour during the evening.
Morning counts for both hemispheres are reduced due to moonlight.
Clear Skies!
Robert Lunsford
AMS Visual Program Coordinator
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