(meteorobs) Meteor Activity Outlook for April 21-27, 2006

[Robert Lunsford]

As some of you may have noticed last week, the name Antihelion has been
restored to those radiants located along the ecliptic, opposite the sun. The
name "eclipticids" proved unpopular so it will no longer be used.

With the arrival of April, observers in the northern hemisphere still suffer
with low sporadic rates, especially during the evening hours. Observers
south of the equator will witness increasing sporadic rates with the maximum
activity occurring in July. The overall meteor activity is better than March
due to the activity of the two major showers; the Lyrids and the Eta
Aquarids. The Antihelion radiant begins the month in the constellation of
Virgo. By the 15th, the Virginid portion of the antihelion activity becomes
quite low and few meteors are seen. During the last week of the month a
strong center of antihelion activity becomes active in the constellation of
Libra. Many of these meteors can be noticed while viewing early Eta Aquarid
activity. Due to the southerly position of the Antihelions this time of
year, they are slightly better seen south of the equator. The most favorable
time to view meteor activity this month would be near the new moon, which
occurs on April 27. April is also prime time for viewing fireballs. No exact
radiant has been determined for these fireballs but a good number of them
are associated with the Antihelion radiant. Therefore the hours near 0200
(local daylight saving time) are the most favorable time to view these
events. Still, many have been witnessed during the early evening hours, when
the radiant area lies low in the southeastern sky.

The moon reaches its last quarter phase on Friday April 21. At that time the
moon will rise near 0100 local daylight time and will remain in the sky the
remainder of the morning. These conditions are not ideal, but successful
observations can still be undertaken if one keeps the bright moon out of
your field of view while observing. The estimated total hourly rates for
evening observers this week is near two for observers in the northern
hemisphere and three for those south of the equator. For morning observers
the estimated total hourly rates should be near twelve 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. Morning rates are
reduced due to moonlight.

The radiant positions listed below are exact for Saturday night/Sunday
morning April 22/23. 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.

The following radiants are active this week:

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 07:24 (111) -45. This
area of the sky is located in southern Puppis, two degrees south 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 Anthelion (ANT) radiant is now centered at 15:00 (225) -17. This area of
the sky is located in central Libra, just a couple of degrees southeast of
the brilliant planet Jupiter. This radiant is best placed near 0200 local
daylight time when it lies on the meridian and is highest in the sky. Rates
should be near two per hour for those north of the equator and three per
hour south of the equator. With an entry velocity of 30 km/sec., the average
Anthelion meteor would be of medium-slow speed. This radiant is a good
source of fireballs now through the end of April.

The Lyrids (LYR) are the first major annual shower of the season. ZHR's
reach one on April 16th and remain at or above this level through April 25.
Peak rates will occur on Saturday 16:30 Universal Time on April 22. This
timing favors the western Pacific area and eastern Asia where local
observers will actually see the best rates on the morning of April 23. At
this time the radiant will be high in the northeast for observers located in
Japan, Korea, and eastern China. The timing also favors Australia but the
radiant will be located low in their northern sky so rates will be much
lower that those seen northward. For North America this time corresponds to
12:30 PM EDT and 9:30 AM PDT on April 22, which of course is during
daylight. The best Lyrid rates seen from North America will occur on the
morning of April 22, during the last dark hour before dawn. Europe will most
likely see their best rates before moonrise on the evening of April 22 and
morning of the 23rd. ZHR's average 18 but raw visual rates can vary from
5-25, depending on your observing conditions. The radiant currently lies at
18:08 (272) +34. This area of the sky is located in eastern Hercules, seven
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 the 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 Eta Aquarids (ETA) are particles from Halley's Comet, which last passed
through the inner solar system in 1986. Even though this is now 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 30 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 21:44 (326) -06. This area of the sky is located in
western Aquarius, eight degrees west 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.

The Sporadic rates for the Northern Hemisphere are now nearing their annual
minimum activity. One would expect to see perhaps four 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 now increasing toward a
secondary maximum in July. One would see approximately six random meteors
per hour during the late morning hours and three per hour during the
evening. Morning rates from all areas are reduced due to moonlight.

Pi Puppids (PPU)  07:20 (110) -45
Northern Hemisphere   >1 - Southern Hemisphere 1

Antihelion (ANT) - 15:00 (225) -17
Northern Hemisphere   2 - Southern Hemisphere  3

Lyrids (LYR) 17:36 (272) +34
Northern Hemisphere   5 - Southern Hemisphere 1

Eta Aquarids (ETA) 21:44 (326) -06
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#X2006

Clear Skies!
Robert Lunsford
American Meteor Society