Meteor Activity Outlook for April 20-26, 2007

April has one major annual shower and the start
of another. The Lyrids are active from April 16-25 and reach maximum activity on
the 22nd. While not the strongest annual shower they produce much better rates
than has been seen for the past three months. The Eta Aquarids also reach a ZHR
of one on April 19 and slowly continue to increase in strength as the month
progresses. Sporadic rates seen in the northern hemisphere are actually worse
than those seen in March. This trend will continue through June. On the other
hand rates seen from the southern hemisphere are increasing toward a July
maximum.

During this period the moon reaches its first
quarter phase on Tuesday April 24. At this time the half illuminated moon will set near 0100 local
daylight time and will not interfere with observing the remainder of the morning.
The estimated total hourly rates for evening observers this week is near two for
those north of the equator and three for observers south of the equator. For
morning observers the estimated total hourly rates should be near twenty no matter
your location. 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 moonlight.

The radiant positions listed below are exact for Saturday
night/Sunday morning April 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. Doing this 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 Pi Puppids (PPU) is a relatively new shower with most of the activity
occurring when the parent comet (26P Grigg-Skjellerup) is near perihelion.
This comet will next be at perihelion in March 2008 so a trace of activity
from this shower is not out of the question. The radiant for this shower
lies far to the south and is nearly impossible to detect north of thirty
degrees north latitude. The radiant position lies at 07:18 (110) -45. This
area of the sky is located in southern Puppis, two degrees southwest of the
third magnitude star Sigma Puppis. The radiant lies highest in a dark sky as
soon as it becomes dark at the end of evening twilight. Peak activity occurs
on April 23. Away from this night rates are expected to be far less than one
per hour. With an entry velocity of only 18 kilometers per second, these
meteors will appear to move very slowly. Shower members are usually quite
bright which may also aid in their identification.

The Antihelion (ANT) radiant is now centered at 14:56 (224) -16. This area
of the sky is centered in western Libra, close to the third magnitude star
Zubenelgenubi (Alpha Librae). This radiant is best placed near 0200 LDT when it
lies on the meridian and is highest in the sky. Rates at this time should be near
one per hour as seen in the northern hemisphere and two per hour for those located
south of the equator. With an entry velocity of 30 km/sec., the average antihelion
meteor would be of medium-slow speed.

The Lyrids (LYR) are the first major annual shower of the season. ZHR’s
reached one on April 16th and remain at or slightly above this level through April
25. According to the IMO, peak rates will occur on Sunday April 22 near 22:30
Universal Time. This timing favors Asia where local observers will actually see
the best rates on the morning of April 23. For North America this time corresponds
to 6:30 PM EDT and 3:30 PM PDT on April 22, which of course is during daylight.
Peak Lyrid rates seen from North America should be similar on both the mornings
of the 22nd and 23rd. ZHR’s average eighteen but raw visual rates can vary from
5-25, depending on your observing conditions. The radiant currently lies at 18:04
(271) +34. This area of the sky is located in eastern Hercules, eight degrees
southwest of the brilliant zero magnitude star Vega (Alpha Lyrae). The radiant
rises in the northeastern sky during the late evening hours for most locations in
the Northern Hemisphere. One should wait until the radiant reaches an elevation of
thirty degrees before commencing observations. At lower radiant elevations only
a small fraction of the Lyrid activity can be seen. For 30 degrees north latitude
this occurs near midnight. The radiant would reach thirty degrees elevation
earlier for locations further north and later for locations further south.
The best time to view this activity is just before the start of morning twilight,
when the radiant lies highest in a dark sky. With an entry velocity of 49
kilometers per second, a majority of these meteors will appear to move with
moderate to swift speeds. The Lyrids are also known to produce a fair amount of
meteors with persistent trains and an occasional fireball.

The The Eta Aquarids (ETA) are particles from Halley’s Comet, which last
passed through the inner solar system in 1986. Even though this is now over twenty
years ago, material is still encountered every year in late April and throughout
most of May. We pass closest to Halley’s orbit on May 6. At that time Eta
Aquarid rates can reach thirty shower members per hour as seen from the northern
tropical areas southward. Current rates would be less than one per hour from
a radiant located at 21:36 (324) -07. This area of the sky is located in
western Aquarius, one degree southeast of the third magnitude star Sadalsuud
(Beta Aquarii). The best time to view this activity is just before the start
of morning twilight, when the radiant lies highest in a dark sky. With an
entry velocity of 66 kilometers per second, a majority of these meteors will
appear to move swiftly.

Sporadic rates are slowing decreasing for observers in the northern
hemisphere and slightly rising for those south of the equator. One would expect
to see perhaps seven random meteors during the last hour before dawn from rural
observing sites located in the northern hemisphere. During the first dark hour
after the end of evening twilight, perhaps one random meteors can be seen per
hour. Sporadic rates increase as the night progresses so rates seen near
midnight would be near four per hour. Late morning sporadic rates seen from the
southern hemisphere are now near thirteen per hour from rural observing sites.
During the first dark hour after the end of evening twilight, perhaps two
random meteors can be seen per hour, increasing to eight by midnight. Evening
rates are reduced due to moonlight.