(meteorobs) Meteor Activity Outlook for January 14-20, 2005

Robert Lunsford lunro.imo.usa at cox.net
Wed Jan 12 16:00:45 EST 2005


This upcoming period will see the moon reaching its first quarter phase on
Monday January 17.  At this time the moon will set near midnight leaving the
morning hours free of interfering moonlight. The estimated total hourly
rates for evening observers this week should be near two for those in the
Northern Hemisphere and three for those observers south of the equator. For
morning observers the estimated total hourly rates should be near thirteen
for those located in the Northern Hemisphere and fifteen for those in the
Southern Hemisphere. Rates are reduced during the evening 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 January 15/16. 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 08:40 (130) +18. This area of the
sky is located in central Cancer, very close to the fourth magnitude Delta
Cancri. Since this radiant is large and diffuse, any slow to medium speed
meteor from northeastern Canis Minor, eastern Gemini, northwestern Hydra,
western Leo or Cancer 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 two shower
members per hour from the Northern Hemisphere and one per hour 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. 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
Delta Cancrids (DCA).

The Gamma Velids (GVE) are the first of many weak southern showers active
during January and February. The Gamma Velids are listed among the radiants
of the Dutch Meteor Society and reached maximum activity on January 5.
Current rates would be low, most likely less than one shower member per
hour. The radiant is currently located near 08:44 (131) -49. This position
lies in central Vela, six degrees north of the second magnitude star Delta
Velorum.  The radiant lies highest in the sky between 0100 and 0200. This
shower is not visible north of latitude 45 north. At 35 km/sec. the Gamma
Velids produce meteors of average velocity.

The Alpha Hydrids (AHY) is another shower listed among radiants of the Dutch
Meteor Society. The date of maximum activity is January 14 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 08:56
(134) -11. This position lies in western Hydra eight 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 is January 15 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 12:52 (193) -63. This position lies in extreme
southeastern Crux, three degrees east of the first magnitude star Acrux
(Alpha Crucis). 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 Coma Berenicids (COM) are active from a radiant located at 13:16 (199)
+15. This area of the sky lies on the Coma Berenices/Virgo border, five
degrees northeast of the third magnitude star Vindemiatrix (Epsilon
Virginis). This radiant is best placed for viewing just before dawn, when it
lies highest above the horizon. The predicted date of maximum activity was
December 19, when the predicted ZHR reached five. Current rates are most
likely less than one per hour. At 65 km/sec. the Coma Berenicids produce
mostly swift meteors with the brighter shower members leaving persistent
trains.

The Sporadic rates for the Northern Hemisphere are now just past their
annual peak. One would expect to see perhaps ten random meteors per hour
during the last hours before dawn from rural observing sites. During the
evening hours perhaps two random meteors can be seen per hour. Sporadic
rates seen from the Southern Hemisphere are increasing toward a peak this
month. One would see approximately twelve random meteors per hour during the
late morning hours and three per hour during the evening. Rates are reduced
during the evening due to moonlight


Anthelion        Radiant Position  = 08:40  (130) +18
Hourly Rate = 3  N. Hemisphere, 2  S. Hemisphere

Gamma Velids (GVE)   Radiant Position  = 08:44 (131)  -49
Hourly Rate = 0  N. Hemisphere, <1  S. Hemisphere

Alpha Hydrids (AHY)   Radiant Position  = 08:56 (134)  -11
Hourly Rate = <1  N. Hemisphere, <1  S. Hemisphere

Alpha Crucids (ACR)   Radiant Position  = 12:52 (193)  -63
Hourly Rate = 0  N. Hemisphere, 1  S. Hemisphere

Coma Berenicid (COM)   Radiant Position  = 13:16 (199)  +15
Hourly Rate = <1  N. Hemisphere, <1  S. Hemisphere

Clear Skies!
Robert Lunsford
American Meteor Society



More information about the Meteorobs mailing list