(meteorobs) Meteor Activity Outlook for February 21-27, 2009

[Robert Lunsford]

February is the only month of the year that sees a fall in rates in both
hemispheres. As seen from the northern hemisphere, sporadic rates continue
the fall that began in January. This will continue until June when rates
reach their nadir. After a brief peak of activity in January, sporadic rates
in the southern hemisphere also slide downward until March. Shower activity
is low this month but decidedly more interesting in the southern hemisphere.
During February there are several sources of activity in the southern
morning sky. Most notable is the Alpha Centaurids, which are active during
the entire month of February. Other sources are scattered from Carina
through Puppis, Vela, and on into Centaurus and Lupus. None of these even
rate as a minor shower but together, along with the Alpha Centaurids, create
some interesting viewing during the summer nights south of the equator. Only
a trace of this activity can be seen from the northern tropics. The
Antihelion radiant remains north of the celestial equator and produces a
modest 1-2 meteors per hour from Leo. The weak Delta Leonids become active
at mid-month but are few and far between, even at maximum activity.

During this period the moon reaches it new phase on Wednesday February 25th.
At this time the moon lies near the sun in the sky and is not visible at
night. This weekend the waning crescent moon will cause no interference for
the meteor observer. The estimated total hourly rates for evening observers
this week is near three as seen from the northern hemisphere and four for
those situated south of the equator. For morning observers the estimated
total hourly rates should be near thirteen for those located in the
mid-northern hemisphere (45 N) and sixteen for those viewing from the
mid-southern hemisphere (45 S). Locations between these two extremes would
see activity between the listed figures. 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 and rates listed below are exact for Saturday
night/Sunday morning February 21/22. 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. Viewing there 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.

The following showers are expected to be active this week:

The weak Delta Leonids (DLE) reach maximum on Wednesday February 25th.
Visual rates will only be near one per hour at this time, no matter your
location. The radiant is now located at 11:00 (165) +18. This area of the
sky lies in central Leo, four degrees northwest of the third magnitude star
Theta Leonis. This radiant is best placed near 0100 local standard time when
it lies on the meridian and is highest in the sky. With an entry velocity of
23 km/sec., the average Delta Leonid meteor would be of slow speed. Do not
confuse these meteors with the overlapping Antihelion radiant, whose center
lies thirteen degrees to the south. To separate these meteors, the observer
must be facing in a direction that allows both radiants to be included
within your field of view.

The wide Antihelion (ANT) radiant is now centered at 11:04 (166) +05. This
area of the sky lies in a remote area of southeastern Leo. The nearest
easily seen star is fourth magnitude Sigma Leonis, located three degrees
northeast of the center of the radiant. This radiant is best placed near
0100 LST, when it lies on the meridian and is located highest in the sky.
Due to the large size of this radiant, any meteor radiating from southern
Leo, western Virgo, or Sextans could be a candidate for this shower. 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 Gamma Normids (GNO) reach an ZHR of one on Wednesday February 25th. At
that time the radiant is located at 14:48 (222) -52. This area of the sky is
located in southern Lupus, four degrees southeast of the second magnitude
star Alpha Lupi. Current visual rates would be less than one shower member
per hour, no matter your location. These meteors are best seen between 0400
and 0500 local standard time, when the radiant lies highest above the
horizon. This shower is best seen from the southern hemisphere, where the
radiant lies high in the sky at dawn. Meteors from this shower are not
visible north of 40 degrees north latitude and also poorly seen throughout
most of the northern hemisphere. An occasional shower member may be seen
from the northern tropics, shooting upwards from the southern horizon. At 56
km/sec. the Gamma Normids will usually produce meteors of swift velocity.

As seen from the mid-northern hemisphere (45N) one would expect to see
approximately ten Sporadic meteors per hour during the last hour before dawn
as seen from rural observing sites. Evening rates would be near two per
hour. As seen from the mid-southern hemisphere (45S), morning rates would be
near thirteen per hour as seen from rural observing sites and three per hour
during the evening hours. Locations between these two extremes would see
activity between the listed figures.

The table below presents a summary of the expected activity this week. Rates
and positions are exact for Saturday night/Sunday morning but may be used
all week.

Delta Leonids (DLE) - 11:00 (165) +18  Velocity - 23km/sec.
Hourly Rates - Northern Hemisphere - 1   Southern Hemisphere - 1

Antihelion (ANT) - 11:04 (166) +05   Velocity - 30km/sec.
Hourly Rates - Northern Hemisphere - 2   Southern Hemisphere - 2

Gamma Normids (GNO)  14:48 (222) -52   Velocity - 56km/sec.
Hourly Rates - Northern Hemisphere - <1   Southern Hemisphere - <1

*For a detailed explanation on the different classes of meteor showers and
other astronomical terms, please visit:
http://www.amsmeteors.org/showers.html#X2009

Clear Skies!
Robert Lunsford
American Meteor Society