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(meteorobs) Meteor Activity Outlook for Jan 23-29, 2004
The moon reaches its first quarter phase on Thursday January 29. At this
time the moon lies approximately ninety degrees east of the sun and sets
near local midnight. This weekend the waxing crescent moon will set during
the early evening hours and will not be much of a problem at all. The
estimated total hourly rates for evening observers this week should be near
two for those in the Northern Hemisphere and three for those south of the
equator. For morning observers the estimated total hourly rates should be
near twelve for those located in the Northern Hemisphere and fifteen for
those in the Southern Hemisphere. 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 January 24/25. The radiants do not change greatly day to day so the
given positions may be used during this entire period. Most star atlases
(available at science stores and libraries) 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 location. 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 last rise later in the night. This list also
provides the order of ascending velocity for each radiant with those listed
first usually being much slower than those last on the list. Velocity should
not be the prime factor for shower association as all showers can produce
slow meteors. Slow meteors can be produced from normally swift showers, such
as the Leonids, when meteors appear near the radiant or close to the
horizon. The true velocity is only revealed in shower members seen far from
the radiant and high in the sky.
The Alpha Carinids (ACN) is a shower listed among radiants of the Dutch
Meteor Society. The date of maximum activity was January 31 with a predicted
ZHR of two. Current rates would be most likely less than one shower member
per hour. With such low activity care must be taken to exclude any sporadic
activity from the Alpha Carinid count. The radiant currently lies at 06:12
(093) -54. This position lies in western Carina, only one degree southwest
from the brilliant negative one magnitude star Canopus (Alpha Carinae). This
radiant is only seen well from the northern equatorial regions southward.
The area of the sky is also best placed near 2200 (10pm) local standard
time. At 25 km/sec. the Alpha Carinids produce meteors of slow velocity.
The Delta Velids (DVE) is another shower listed among radiants of the Dutch
Meteor Society. The date of maximum activity is February 15 with a predicted
ZHR of one. Current rates would be less than one shower member per hour.
With such low activity care must again be taken to exclude any sporadic
activity from the Delta Velid count. The radiant currently lies at 08:04
(121) -46. This position lies on the Puppis/Vela border, very close to the
second magnitude star Gamma Velorum. Like the Alpha Carinids, this radiant
is only seen well from the northern equatorial regions southward. The area
of the sky is also best placed near midnight local standard time. At 35
km/sec. the Delta Velids produce meteors of average velocity.
The Antihelion radiant is now centered at 09:16 (139) +15. This area of the
sky is located in eastern Cancer, very close to the faint star Pi2 Cancri.
Since this radiant is large and diffuse, any slow to medium speed meteor
from eastern Cancer or western Leo could be a candidate for this shower. The
center of this area is best placed near 0100 local standard time when it
lies on the meridian and is highest in the sky. At this time expect to see
three shower members per hour from areas north of the equator and one per
hour for locations south of the equator.
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. 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 antihelions 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. Those who send their data to the International Meteor Organization
should call these meteors Delta Cancrids (DCA).
The Alpha Hydrids (AHY) is another shower listed among radiants of the Dutch
Meteor Society. The date of maximum activity was January 15 with a predicted
ZHR of two. Current rates would be most likely less than one shower member
per hour. With such low activity care must be taken to exclude any sporadic
activity from the Alpha Hydrid count. The radiant currently lies at 09:20
(140) -14. This position lies in western Hydra five degrees southwest of the
second magnitude star Alphard (Alpha Hydrae). This radiant is seen equally
well from both hemispheres. The area of the sky is also best placed near
0200 local standard time. At 44 km/sec. the Alpha Hydrids produce meteors of
average velocity.
The Alpha Crucids (ACR) is yet another shower listed among the radiants of
the Dutch Meteor Society. The date of maximum activity was January 16 with a
predicted ZHR of three. Like the previous weak showers, care must be taken
to exclude any sporadic activity from the Alpha Crucid count. The radiant
currently lies at 13:28 (202) -67. This position lies in northeastern Musca,
some two degrees northeast of the faint star Eta Muscae. Due to the far
southern declination this shower is not well seen north of the northern
equatorial regions. The area of the sky is also best placed just before dawn
when it lies highest in the sky. At 50 km/sec. the Alpha Crucids produce
meteors of medium swift velocity.
The Theta Centaurids is the first of several radiants that are active in
Centaurus during late January and throughout the month of February. The date
of maximum activity is February 15 with a predicted ZHR of four. Current
ZHR's would be near one. The radiant lies at 12:28 (187) -33. This position
is in eastern Hydra, ten degrees south of the third magnitude star Beta
Corvi. This shower is not well seen north of the northern tropical regions.
It is possible to see activity from the latitude of San Diego, CA as I have
witnessed several of these meteors during my winter observations. This area
of the sky is best placed near 0500 local standard time when it lies highest
in the sky. At 60 km/sec. the Theta Centaurids produce meteors of swift
velocity.
The Northern Apex radiant is now centered at 14:16 (214) +02. This position
lies in eastern Virgo, three degrees northeast of the fourth magnitude star
Tau Virginis. This area of the sky is best placed for viewing during the
last dark hour before dawn when it lies highest in the sky. Since this
radiant is large and diffuse, any meteor from eastern Virgo, southwest
Serpens Caput, northwestern Libra or southeastern Bootes could be a
candidate from this source. Rates would be now close to two per hour
regardless of your location.
Like the antihelion area, both apex areas 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. This is
not really a "shower" per se, but an artificial radiant created by the
Earth's motion through space. Meteors from both branches are normally
included in the sporadic count. I feel it is a worthy project to see if it
is possible to distinguish these meteors from the normal sporadic
background. On rare occasions there are meteors with a zero inclination that
radiate precisely from the apex point on the ecliptic, exactly 90 degrees
west of the sun. In simplistic terms, these meteors are seldom seen since
the Earth "sweeps clean" much of the material that shares the same orbit as
our planet. Much more material 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.
The Southern Apex source lies exactly 30 degrees south of its northern
counterpart at 14:16 (214) -28. This position lies in easternmost Hydra some
two degrees southeast of the third magnitude star Pi Hydrae. Like the
northern apex, these meteors are best seen toward dawn when the radiant lies
highest above the horizon in a dark sky. Since this radiant is also large
and diffuse, any meteor from northern Centaurus, southwestern Libra, eastern
Hydra or southern Virgo could be a candidate from this source. Rates would
be now close to one per hour in the Northern Hemisphere and two per hour in
the Southern Hemisphere.
The Sporadic rates for the Northern Hemisphere are now past their annual
peak. One would currently expect to see perhaps seven 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 two
random meteors can be seen per hour from the Northern Hemisphere. Rates seen
from the Southern Hemisphere are now slightly stronger than those seen in
the northern skies with perhaps eight random meteors being seen per hour
during the early morning hours and three per hour during the evening.
Meteors from Coma Berenices? Alastair McBeath, vice president of the
International Meteor Organization, issued an observing alert in 2001 for
possible meteors from the constellation of Coma Berenices. Little or nothing
was seen that year but the possibility exists that renewed activity may
again occur some year around this time. The suspected radiant lies in
central Coma at 12:32 (188) +22. Maximum activity is expected on January 25,
but observations before and after this date are very important too! The
radiant is in the sky all morning long but is best placed near 0400 local
time when it lies on the meridian. This would be in a due south direction
for observers north of 22 degrees N. latitude and due north for observers
south of 22 degrees N. latitude. With an entry velocity near 60 km/sec.
these meteors would appear to travel slowly if seen near the radiant or near
the horizon. If seen far from the radiant and high in the sky then they
would appear to travel quite swiftly. Rates are expected to be low but even
a report of zero activity is important. Video, photographic, and plotting
would be valuable activities in order to confirm any activity. This is one
case where observers MUST face close to the radiant to help determine shower
association. Looking further than 15 degrees away from the radiant
introduces a greater possibility of sporadic meteors being recorded as
shower members. Let us know what you see or don't see as soon as possible!
Clear Skies!
Robert Lunsford
AMS Operations Manager
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