(meteorobs) Meteor Activity Outlook for June 17-23, 2005

Robert Lunsford lunro.imo.usa at cox.net
Thu Jun 16 12:18:43 EDT 2005


This upcoming period will see the moon reaching its full phase on
Tuesday June 21. At this time the moon rises as the sun sets and sets as the
sun rises. There is a small window of opportunity to view in dark skies
early in this period as there will be an hour or two between moonset and the
start of morning twilight. The estimated total hourly rates for evening
observers this week should be near one for those in the Northern Hemisphere
and two for those observers south of the equator. For morning observers the
estimated total hourly rates should be near seven for those located in the
Northern Hemisphere and nine for those in the Southern Hemisphere. Evening
rates are reduced due to moonlight. 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 listed below are exact for Saturday night/Sunday
morning June 18/19. 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. 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.

These are the showers that may be observed this week:

The Anthelion radiant is now centered at 18:48 (282) -23. This area of the
sky is located in central Sagittarius, four degrees northeast of the third
magnitude star Lambda Sagittarii. Since this radiant is large and diffuse,
any slow to medium speed meteor from northern Sagittarius, southern Scutum
or southern Serpens Cauda could be a candidate for this shower. The center
of this area is best placed near 0200 local daylight time when it lies on
the meridian and is highest in the sky. At this time expect to see two
shower members per hour from the Southern Hemisphere and one from the
Northern.

Unlike most of the annual showers the antihelion source is produced by
debris from unknown objects orbiting in a direct motion like the earth.
These objects are most likely asteroids, which produce stony and metallic
debris whose density is much greater than material produced by comets. There
is also the possibility that some of this activity may be caused by the
"Jupiter family of comets", comets which have been altered by Jupiter's
gravity into much shorter orbits. This material 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 source is active
all year from an area of the sky nearly opposite that of the sun. The center
of this source will move approximately one degree eastward per day and
travels through many different constellations over the course of a year. It
may make sense to list these meteors as anthelions or "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. Observers who send their reports to the
International Meteor Organization (I.M.O.) should label these meteors as
Sagittarids (SAG).

The June Lyrids (JLY) / Xi Draconids (XDR) reach maximum activity in
mid-June. After its 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 near Draco's head in 1996, active
between June 11 and the 17th. These meteors were much more numerous than the
June Lyrids that year and have continued to provide more activity than its
southerly neighbor ever since. The current radiant positions for the June
Lyrids is 18:48 (282) +35 and 18:48 (282) +55 for the Xi Draconids. These
positions lie on the in central Lyra (four degrees southeast of Vega) and in
southern Draco, ten degrees southeast of the 4th magnitude star Xi Draconis,
the northernmost star in the "Lozenge" (head) of Draco. As seen from the
Northern Hemisphere these radiants lie high in the sky passing nearly
overhead during the short nights that occur this time of year. They are well
placed between 0100 and 0200 when they lie highest above the horizon. They
lie much lower in the sky as seen from the Southern Hemisphere and are not
well seen. Meteors from both radiants are somewhat swift unless seen near
the radiant or low in the sky. Please keep an eye out for this activity and
let us know which radiant is active for you.

The Arietids (DAR) are active from a radiant located approximately thirty
degrees west of the sun. The radiant rises just before the start of morning
twilight and any activity would be seen shooting upwards from the
northeastern horizon. These meteors are of medium velocity and usually last
several seconds as they skim the outer regions of the earth's atmosphere.
The current radiant position is located at 03:28 (052) +31 which is located
on the Aries-Taurus-Perseus border some seven degrees northwest of the
Pleiades star cluster. This shower peaked on June 7 with a ZHR of 60. Even
with such strong rates the unfavorable altitude at the time of daybreak
makes seeing this activity a difficult challenge. On the other hand, those
with radio meteor equipment can easily detect this activity as it is the
strongest annual radio meteor shower of the year.

The Sporadic rates for the Northern Hemisphere are now reaching their low
plateau for the year. Observers can expect around five random meteors per
hour during the morning hours as seen from locations in the Northern
hemisphere. During the dark evening hours perhaps one random meteor can be
seen per hour north of the equator. Sporadic rates seen from the Southern
Hemisphere are slowly increasing toward a July maximum. From south of the
equator one would expect to see approximately seven random meteors per hour
during the late morning hours and two per hour during the evening. Evening
rates are reduced due to moonlight.

Anthelion  (Sagittarids)    18:48 (282) -23
Hourly Rate =     1   N. Hemisphere,    2  S. Hemisphere

June Lyrids  (JLY)    18:48 (282) +35
Hourly Rate =    >1   N. Hemisphere,    0  S. Hemisphere

Xi Draconids  (XDR)    18:48 (282) +55
Hourly Rate =     1   N. Hemisphere,    0  S. Hemisphere

Arietids (DAR)   03:28  (052)  +31
Hourly Rate =    >1  N.  Hemisphere,   0  S. Hemisphere

Clear Skies!
Robert Lunsford
American Meteor Society
http://www.amsmeteors.org/lunsford/



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