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(meteorobs) Meteor Activity Outlook for June 15-21, 2001
The moon is now a waning crescent and will reach new on Thursday June
21. This week and next will offer the best observing conditions for the
month. This is prime observing time for observers in the far Southern
Hemisphere as the nights are at their longest this time of year. Just
the opposite occurs for far Northern Hemisphere observers who now suffer
through short nights and eternal twilight. This is the one time of the
year when man-made satellites may be seen all night long in the Northern
Hemisphere. Even from middle northern latitudes satellites may be
glimpsed near midnight low in the northern skies.
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 slight lunar
interference so the estimated total hourly rates should be near 7 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 16/17. 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 18:40 (280) -23. This area of
the sky is located in northern Sagittarius only 1 degree northeast of
the famous brilliant globular cluster M22. Any slow to medium speed
meteor from northern Sagittarius or southern Scutum 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) and Gamma
Sagittarids for the DMS.
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 position
for the June Lyrids is 18:36 (279) +35 and 18:36 (279) +55 for the Xi
Draconids. These positions lie in Lyra just 4 degrees south of the
brilliant zero magnitude star Vega (Alpha Lyrae) and in the area just
east of 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. Meteors from both radiants are
somewhat swift unless seen near the radiant or low in the sky. Expect to
see perhaps 1 meteor from one of these sources each hour unless an
unexpected outburst occurs. The best activity would be expected to occur
on Friday night /Saturday morning June 15/16. Any repeat of Marco
Langbroek's 1996 outburst would be centered near 06:15 UT on the 16th
which corresponds to 02:15 EDT Saturday morning and 11:15 PDT Friday
evening for those in American time zones. Please keep a watch for this
activity and let us know which radiant produces the most activity for
you.
The Tau Aquarids are listed among the radiants of the Dutch Meteor
Society. Their studies indicate a ZHR of 3 at maximum activity on June
29. Current rates would be less than 1 per hour. The radiant position is
22:00 (330) -17. This position is located in southwestern Aquarius 4
degrees west of the 3rd magnitude star Delta Capricorni. With an entry
velocity of 63 kilometers per second these meteors would move swiftly
if seen far from the radiant and high in the sky. Like the Apex radiants
this activity would be best seen during the last few hours before dawn.
The Northern Apex radiant is now located at 23:40 (355) +13. This
position lies in southern Pegasus (just south of the "Great Square" some
3 degrees east of the 4th magnitude star 70 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 23:40 (355) -17. This position lies in southeastern
Aquarius 2 degrees south of the the 4th magnitude star Omega 2 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
southeastern Aquarius, northern Sculptor, or western Cetus could
be a candidate from this source. Rates should be close to 1 per hour as
seen from the lower Northern Hemisphere and all of the Southern
Hemisphere. Those reporting data to the Dutch Meteor Society should
now list these meteors as Tau Cetids.
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 03:24 (051) +29 which is on
the Aries/Taurus border some 6 degrees northwest 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 4 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 5 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 slightly due to
moonlight.
Clear Skies!
Robert Lunsford
AMS Visual Program Coordinator
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