(meteorobs) Meteor Activity Outlook for February 15-21, 2008

[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 2-3 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 its full phase on Thursday February
21st. At this time the moon will be located opposite the sun and will be in
the sky all night long. During this upcoming weekend the waxing gibbous moon
will set early during the morning hours and will allow for a few hours of
dark sky viewing before the onset of dawn. The estimated total hourly rates
for evening observers this week is near two no matter your location. For
morning observers the estimated total hourly rates should be near twelve for
those located in the mid-northern hemisphere (45 N) and fifteen for those
viewing from the mid-southern hemisphere (45 S). 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. Evening rates are reduced due to the bright moonlight.

The radiant positions and rates listed below are exact for Saturday
night/Sunday morning February 16/17. 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 wide Antihelion (ANT) radiant is now centered at 10:44 (161) +06. This
area of the sky lies in southern Leo, ten degrees southeast of the bright
star Regulus (alpha Leonis). This radiant is best placed near 0100 local
standard time when it lies on the meridian and is highest in the sky.
Actually any meteor from northern Sextans or southern Leo could be a
candidate for this shower. Rates at this time should be near two per hour as
seen from the northern hemisphere and one per hour for observers located
south of the equator. With an entry velocity of 30 km/sec., the average
Antihelion meteor would be of medium-slow speed.

The Delta Leonids (DLE) reach a ZHR of one on February 15. Visual rates will
be less than one at this time. The radiant is now located at 10:48 (162)
+19. This area of the sky lies in central Leo, ten degrees northeast of the
bright star Regulus (alpha 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 medium-slow speed.

The Alpha Centaurids (ACE) are active from a radiant located at 14:48
(222) -62. This area of the sky is located in southeastern Centaurus, just
south of the brilliant star Rigel Kentaurus (alpha Centauri). Current rates
would be near one shower member per hour. These meteors are best seen near
0500 local standard time when the radiant lies highest above the horizon.
This shower is not visible north of 28 degrees north latitude and also
poorly seen in the northern tropics. The southern hemisphere offers a much
better view of this activity as the radiant lies much higher in the southern
sky. Those located at high southern latitudes will actually encounter
morning twilight before the radiant reaches culmination. At 56 km/sec. the
Alpha Centaurids will usually produce meteors of swift velocity.

Sporadic rates are now slowly falling no matter your location. One would
expect to see approximately ten random meteors during the last hour before
dawn from rural observing sites in the northern hemisphere and thirteen from
the southern hemisphere. During the first dark hour after the end of evening
twilight, perhaps two random meteors can be seen per hour, no matter your
location.

The table below presents a condensed version of the expected activity this
week. Rates and positions are exact for Saturday night/Sunday morning.

Antihelion (ANT) - 10:44 (161) +06   Velocity - 30km/sec.
Northern Hemisphere -  2   Southern Hemisphere - 1

Delta Leonid (DLE)  10:48 (162) +19 Velocity - 23km/sec.
Northern Hemisphere -  >1   Southern Hemisphere - >1

Alpha Centaurids (ACE)  14:48 (222) -62   Velocity - 56km/sec.
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#X2008

Clear Skies!
Robert Lunsford
American Meteor Society