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(meteorobs) Meteor Activity Outlook for January 18-24, 2002

The moon reaches its first quarter phase on Monday January 21. At this 
time it will set near midnight local time allowing morning observers a 
unhampered view of the mid January activity. The estimated total hourly 
rates for evening observers this week should be near 2 northern 
observers and 3 for those located south of the equator. For morning 
observers the estimated total hourly rates should be near 11 for the 
Northern Hemisphere and 14 for those located 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. Moonlight reduces
the activity seen during the evening hours.

The positions listed below are exact for Saturday night/Sunday morning 
January 19/20. The positions do not change greatly day to day so they 
may be used during this entire period. Most star atlas's (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 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 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 would 
be seen 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 Gamma Velids are near the end of its activity period. Maximum 
activity was predicted for January 5 with a zenith hourly rate of only 
2. The radiant is currently located at 08:48 (132) -50 which places it 
in southwestern Vela 5 degrees north of the 2nd magnitude star Delta 
Velorum. This area of the sky is best placed near 0100 local time. I 
would not expect any of this activity to be seen from the Northern 
Hemisphere and rates of less than 1 per hour from far southern observing 
sites. The Gamma Velids are of medium velocity when seen high in the
sky, far from the radiant. Care must be taken with this shower and all 
weak showers as the chances of sporadics lining up with the radiant are 
as great as the possibility of actual shower members being produced.

The Antihelion radiant is now located at 08:56 (134) +17. This area of 
the sky is located in central Cancer some 4 degrees southeast of the 4th 
magnitude star Delta Cancri. Any slow to medium speed meteor from Cancer 
or western Leo could be a candidate for this shower. This 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 at least 
2 shower members per hour from locations in the Northern Hemisphere. 
Observers south of the equator will most likely be limited to 1 per hour 
or less, owing to the lower radiant altitude. 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. Those who share reports with the I.M.O. should label these 
meteors as Delta Cancrids (DCA).

The Alpha Hydrids is another obscure winter shower listed among the 
radiants of the D.M.S. Maximum activity is reported to occur on January 
14 with a maximum zenith hourly rate of 2. The radiant is located at 
09:08 (137) -13. This area of the sky is located in southwestern Hydra 
some 5 degrees southwest of the bright orange star Alphard (Alpha 
Hydrae). It reaches the meridian near 0100. At this time it is located 
highest in the sky and best placed for viewing. Any shower members would 
also have medium velocities.

The Alpha Crucids is another obscure southern radiant producing little 
activity. Australian observers report a maximum zenith hourly rate of 3. 
Maximum activity occurs on January 15 so visual rates this week would 
most likely be near 1 per hour for far southern viewers. The Alpha 
Crucid radiant is located at 13:08 (197) -65. This area of the sky is 
located in northeastern Musca 6 degrees southeast of the 1st magnitude 
star Alpha Crucis. This area of the sky is not visible north of 25 
degrees north latitude and is best seen from far southern locations
just before dawn. These meteors are of medium velocity comparable to the 
better- known Lyrids of April. The Northern Apex radiant is now located 
at 13:56 (209) +04. This position lies in north central Virgo 2 degrees 
north of the 4th magnitude star Tau Virginis. 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 northern Virgo or southern 
Bootes could be a good candidate for this shower. This source should 
provide 1-2 meteors per hour during the last few hours before dawn 
regardless of your location. Those who send reports to the I.M.O. should 
label these meteors as Coma Berenicids (COM).

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 13:56 (209) -26. This position lies in eastern Hydra 2 
degrees west of the 3rd 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. Any meteor from southern Virgo, 
northeastern Centaurus or eastern Hydra could be a candidate from this 
source. Rates would be close to 2 per hour from the Southern Hemisphere 
and 1 per hour from the Northern Hemisphere.

The Sporadic rates for the Northern Hemisphere are now in decline and 
will do so until June. One would expect to see perhaps 7-8 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 now be a bit 
better than those seen in the Northern Hemisphere with perhaps 8-10 
random meteors being seen per hour during the late morning hours and 2-3 
during the evening hours. Moonlight interferes with evening rates.

Clear Skies!
Robert Lunsford
AMS Visual Program Coordinator

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