(meteorobs) Meteor Activity Outlook for February 18-24, 2005

[Robert Lunsford]

This upcoming period will see the moon reaching its full phase on Thursday
February 24.  At this time the moon will be in the sky all night long making
the observations of meteors quite difficult. This weekend though, the moon
will set early enough to allow some dark skies before the onset of morning
twilight. 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. Evening rates are reduced due to moonlight.
For morning observers the estimated total hourly rates should be near ten
for those located in the Northern Hemisphere and twelve 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 February 19/20. 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 Delta Velids (DVE) is a shower listed among radiants of the Dutch Meteor
Society. The date of maximum activity was February 14 with a predicted ZHR
of one. With such low activity care must be taken to exclude any sporadic
activity from the Delta Velid count. The radiant currently lies at 08:56
(134) -54. This position lies in western Vela, two degrees northeast of the
second magnitude star Delta Velorum. 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 Delta Leonids (DLE) is a weak shower located close to the anthelion
radiant. It has all the characteristics of anthelion meteors so care must be
taken to separate the two sources. The date of maximum activity is February
24 with a predicted ZHR of only two. The radiant currently lies at 10:56
(164) +18. This position lies in central Leo, five degrees northwest of the
third magnitude star Delta Velorum. This area of the sky is best placed near
0100 local standard time. At 23 km/sec. the Delta Leonids produce meteors of
slow velocity.

The Anthelion radiant is now centered at 11:00 (165) +06. This area of the
sky is located in southeastern Leo, five degrees west of the faint star
Sigma Leonis. Since this radiant is large and diffuse, any slow to medium
speed meteor from northeastern northwestern Hydra, southern 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 no matter
your location.

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
Virginids (VIR).

The Theta Centaurids (TCE) is the most northerly of several radiants that
are active in Centaurus during late January and throughout the month of
February. The date of maximum activity was February 14 with a predicted ZHR
of four. The radiant lies at 14:28 (217) -43. This position is in easternl
Centaurus, close to the third magnitude star Eta Centauri. 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. These meteors are impressive as
they shoot upwards from the deep southern skies. Although swift, they can
last several seconds. 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 Alpha Centaurids (ACE) are the strongest of the radiants that are active
in Centaurus during late January and throughout the month of February. The
date of maximum activity was February 8 with a predicted ZHR of seven.
Current rates should be less than one per hour. The radiant lies at 15:00
(225) -63. This position is in central Circinus, four degrees southeast of
the brilliant zero magnitude star Rigel Kentaurus (Alpha Centauri). Due to
the southern declination this shower is not well seen north of the northern
equatorial regions. This area of the sky is also best placed near 0500 local
standard time when it lies highest in the sky. At 56 km/sec. the Alpha
Centaurids produce meteors of swift velocity.

The Sporadic rates for the Northern Hemisphere are now past their annual
peak. One would expect to see perhaps eight 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 also decreasing toward a secondary minimum
in March. One would see approximately ten random meteors per hour during the
late morning hours and three per hour during the evening. Evening rates are
reduced due to moonlight.

Delta Velids(DVE)   Radiant Position  = 08:56 (134)  -54
Hourly Rate = 0  N. Hemisphere, <1  S. Hemisphere

Delta Leonids (DLE)   Radiant Position  = 10:56 (164)  +18
Hourly Rate = 1  N. Hemisphere, <1  S. Hemisphere

Anthelion        Radiant Position  = 11:00  (165) +06
Hourly Rate = 2  N. Hemisphere, 2  S. Hemisphere

Theta Centaurids (TCE)   Radiant Position  = 14:28 (217)  -43
Hourly Rate = <1  N. Hemisphere, 1  S. Hemisphere

Alpha Centaurids (ACE)   Radiant Position  = 15:00 (225)  -63
Hourly Rate = 0  N. Hemisphere, <1  S. Hemisphere

Clear Skies!
Robert Lunsford
American Meteor Society