(meteorobs) Meteor Activity Outlook for February 16-22, 2007

[Robert Lunsford]

February meteor rates will be less than those seen in January for observers
located in the northern hemisphere. Only the weak Delta Leonids are active
this month. Combine this with falling sporadic rates and it is often a
struggle to go out into the cold. The southern hemisphere also experiences a
dip in sporadic rates but the activity from the Alpha Centaurids more than
makes up this difference. Observers south of the equator are encouraged to
take advantage of the warm nights and to view the meteor activity as often
as possible. There are many suspected radiants in the southern sky this time
of year which are in need of study. Only the Alpha Centaurids have been
verified but there may be other centers of activity awaiting discovery.

This week the moon reaches its new phase on Saturday February 17. At this
time the moon will lie close to the sun and will not interfere with
observing anytime during the night. Later next week a waxing crescent moon
will enter the evening sky but will be too thin and will set too early to
cause any problem to meteor observers. The estimated total hourly rates for
evening observers this week is near three for those viewing from the
northern hemisphere and four for those located south of the equator. For
morning observers the estimated total hourly rates should be near twelve for
observers north of the equator and seventeen for those observers viewing
from 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 17/18. 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. It must be remembered that meteor
activity is rarely seen at the radiant position. Rather they shoot outwards
from the radiant so it is best to center your field of view so that the
radiant lies at the edge and not the center. This method will allow you to
easily trace the path of each meteor back to the radiant (if it is a shower
member) or in another direction if it is a sporadic. 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 showers are expected to be active this week:

The Antihelion (ANT) radiant is now centered at 10:48 (162) +06. This area
of the sky lies on the Leo/Sextans border some fifteen degrees southeast of
the first magnitude star Regulus (Alpha Leonis). This radiant is best placed
near 0100 local standard time when it lies on the meridian and is situated
highest in the sky. Rates at this time should be near two per hour no matter
your location. With an entry velocity of 30 km/sec., the average Antihelion
meteor would be of medium-slow speed.

The weak Delta Leonid (DLE) radiant is now located at 10:48 (162) +18. This
position lies in northern Leo near the faint star 51 Leonis. This position
is just twelve degrees north of the Antihelion radiant so great care must be
taken when assigning these meteors. The radiant is best placed near 0100
local standard time when it lies on the meridian and is situated highest in
the sky. Rates at this time should be less than one per hour, no matter your
location. The peak activity occurs on February 25, when the ZHR reaches two.
With an entry velocity of 23 km/sec., the average Delta Leonid meteor would
be of slow speed.

The Alpha Centaurids (ACE) reached maximum activity on February 8 with a ZHR
near five. Current rates would be near two shower members per hour as seen
from the southern hemisphere. This radiant is now centered at 14:52
(223) -63. This area of the sky lies in central Circinus, three degrees
southeast brilliant star Rigel Kentaurus (Alpha Centauri). This radiant is
best placed near 0500 local standard time when it lies on the meridian and
is situated highest in the sky. Unfortunately for northern observers, this
radiant does not rise above the horizon for observers north of latitude 30
north. Therefore only the north tropical areas and points further south can
view this activity. With an entry velocity of 56 km/sec., the average Alpha
Centaurid meteor would be of swift speed.

Sporadic rates are slowing decreasing for observers located in the northern
hemisphere. One would expect to see perhaps ten random meteors during the
last hour before dawn from rural observing sites. During the first dark hour
after the end of evening twilight, perhaps three random meteors can be seen
per hour. Sporadic rates increase as the night progresses so rates seen near
midnight would be near six per hour. Sporadic rates seen from the southern
hemisphere are near the first of two annual maximums. One would expect to
see perhaps thirteen random meteors during the last hour before dawn from
rural observing sites. During the first dark hour after the end of evening
twilight, perhaps four random meteors can be seen per hour, increasing to
eight by midnight.

Antihelion (ANT) - 10:48 (162) +06
Northern Hemisphere - 2   Southern Hemisphere - 2

Delta Leonid (DLE) 10:48 (162) +18
Northern Hemisphere - >1   Southern Hemisphere - >1

Alpha Centaurids (ACE)  14:52 (223) -63
Northern Hemisphere - >1   Southern Hemisphere - 2

*For a detailed explanation on the different classes of meteor showers and
other astronomical terms, please visit:
http://www.amsmeteors.org/showers.html#X2006

Clear Skies!
Robert Lunsford
American Meteor Society