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(meteorobs) Meteor Activity Outlook for February 28-March 6, 2003



The moon reaches its new phase on Monday March 3. At this time the moon
will be located near the sun as seen from the Earth. Therefore it will
rise and set with the sun and will not interfere with meteor observing
this week. The estimated total hourly rates for evening observers this
week should be near two for those in the Northern Hemisphere and three
for those viewing south of the equator. For morning observers the
estimated total hourly rates should be near 9 for those located in the
Northern Hemisphere and 14 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 positions listed below are exact for Saturday night/Sunday morning
March 1/2 The positions do not change greatly day to day so these
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 radiants
below are listed in a west to east manner in order of right ascension
(celestial longitude). The radiants 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 following radiants will be
active this week:

The Delta Leonids peaked on February 25. The current radiant position is
located at 11:32 (173) +14. This area of the sky is located in eastern
Leo, four degrees west of the second magnitude star Denebola (Beta
Leonis). This position is close to the antihelion source so care must be
taken to separate the two. It is quite possible that this radiant is a
northern branch of the antihelion source. The hourly rate, even at
maximum, rarely exceeds one shower member per hour. The best time to
view this activity is near 0100 local time, when the radiant lies on the
meridian and at its highest point in the sky. With an entry velocity of
23 kilometers per second, these meteors will appear to move slowly.

The Antihelion source is now centered at 11:40 (175) +02. This area of
the sky is located in eastern Virgo,   two degrees west of the fourth
magnitude star Beta Virginis. Since this source is large and diffuse,
any slow to medium speed meteor from eastern Leo or western Virgo could
be a candidate for this shower. The area of the sky 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 2 shower members per hour from all
locations.

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 share their reports with the
I.M.O. should call these meteors Virginids or "VIR".

The Theta Centaurids was the first and is also the last of several
radiants that are active in Centaurus from late January through early
March. The date of maximum activity was February 14 with a predicted ZHR
of 4. Current ZHR's would be less than 1. The radiant currently lies at
15:12 (228) -48. This position is in central Lupus close to the fourth
magnitude star Mu Lupi. Due to the southern declination this shower is
not well seen north of the northern tropical regions. 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 normally produce meteors of
swift angular velocities.

The Gamma Normids are active from a radiant located at 15:44 (236) -52.
This position lies in western Norma, four degrees southwest of the
fourth magnitude double star Gamma Normae. Since the date of maximum
activity is not until March 14, current ZHR's would be less than 1.  Due
to the southern declination this shower is not well seen north of the
northern equatorial regions. This area of the sky is best placed near
0600 local standard time when it lies highest in the sky. At 56 km/sec.
the Gamma Normids normally produce meteors of swift angular velocities.

The Northern Apex source is now centered at 16:40 (250) -07. This
position lies in western Ophiuchus some 4 degrees north of the fourth
magnitude star Zeta Ophiuchi. This area of the sky is best placed for
viewing during the last dark hour before dawn. Since this source is
large and diffuse any meteors from northeastern Libra, southern Serpens
Caput, southwestern Hercules or northwestern Scorpius could be a good
candidate for this shower. This source should provide at least 2 meteors
per hour no matter your location.

Like the antihelion source 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. 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 could 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 16:40 (250) -37. This position lies in central Scorpius,
three degrees southwest of the second magnitude star Epsilon Scorpii.
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
central Scorpius could a candidate from this source. Rates should be
near 3 per hour from the Southern Hemisphere and less than 1 per hour
from the Northern Hemisphere.

The Sporadic rates for the Northern Hemisphere are now slowly declining
and will do so until June. One would expect to see perhaps 5-6 random
meteors per hour during the last hours before dawn from rural observing
sites. During the evening hours perhaps 1-2 random meteors can be seen
per hour. Rates seen from the Southern Hemisphere would be approximately
7-8 random meteors being seen per hour during the late morning hours and
2-3 during the evening hours.

Clear Skies!
Robert Lunsford
AMS Operations Manager

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