(meteorobs) Meteor Activity Outlook for April 17-23, 2010

Robert Lunsford lunro.imo.usa at cox.net
Sat Apr 17 17:05:17 EDT 2010


Meteor activity picks up a bit during April as two major showers are active during the month. The first of these, the Lyrids, are
active from the 16th through the 25th, with a pronounced maximum on the 22nd. The Eta Aquariids start appearing near the 28th and
reach maximum activity during the first week in May. Sporadic rates are low but steady as seen from the mid-northern hemisphere (45
N). Sporadic rates seen from the mid-southern hemisphere (45 S) rise this month toward a maximum in July.

During this period the moon reaches its first quarter phase on Wednesday April 21st. At this time the moon lies ninety degrees east
of the sun and sets near 0100 local daylight time (LDT), depending on your location. This weekend the waxing crescent moon will set
shortly after the end of evening twilight and will not cause any interference to meteor observers. The estimated total hourly rates
for evening observers this week is near two for northern observers and three for those viewing from south of the equator. For
morning observers the estimated total hourly rates should be near ten from the northern hemisphere and fifteen as seen from the
southern hemisphere. 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 and rates listed below are exact for Saturday night/Sunday morning April 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. 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 elusive Pi Puppids (PPU) are now active from a radiant located at 07:12 (108) -46. This area of the sky lies in western Puppis
near the double star Iota Puppi. This radiant is best placed as soon as it becomes dark as it culminates during the afternoon hours
when the sun is still above the horizon. These meteors are nearly non-existent away from the night of April 23rd. Even on that night
it would be lucky to spot just one, especially from the northern hemisphere, where the radiant lies low in the southwest at dusk.
This shower has produced outbursts in the past so it should be monitored whenever possible, especially from the southern hemisphere.
With an entry velocity of only 18 km/sec., the average Pi Puppid meteor would crawl through the sky at a snails pace.

The team of Sirko Molau and Juergen Rendtel have discovered a weak radiant active at this time in the constellation of Virgo. Video
data shows that the Sigma Leonids (SLE) are active from April 18th through the 25th with maximum activity falling on the evening of
April 21st (22nd UT). The radiant is currently located at 13:16 (199) +05. This position lies in central Virgo, five degrees
northeast of the third magnitude star Delta Virginis. The radiant is best placed near midnight LDT, when it lies highest above the
horizon. At 20km/sec. the Sigma Leonids would produce obvious, slow meteors. Expected rates are less than one per hour no matter
your location.

There is also a second new radiant active in Virgo this time of year. Video data shows that the h Virginids (HVR) are active from
April 22-25 with maximum activity occurring on the 22nd. On the evening of the 21st (22nd UT), the radiant is currently located at
14:16 (214) -11. This position lies on the Virgo/Libra border, two degrees southeast of the fourth magnitude star Kappa Virginis.
The radiant is best placed near 0200 LDT, when it lies on the meridian and is highest above the horizon. At 24km/sec. the h
Virginids would produce more obvious, slow meteors. Expected rates would also be less than one per hour no matter your location.

The wide Antihelion (ANT) radiant is now centered at 14:40 (220) -16. This area of the sky lies in western Libra, three degrees west
of the second magnitude star Zubenelgenubi (Alpha Librae). This radiant is best placed near 0200 LDT 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 eastern Hydra, Libra, or eastern
Virgo could be a candidate for this shower. Rates at this time should be near one per hour as seen from the northern hemisphere and
two per hour as seen from south of the equator. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of
medium-slow speed.

The major shower known as the Lyrids (LYR) are active from April 16th through the 25th. Maximum activity occurs on the morning of
April 22th. The radiant is currently located at 18:00 (270) +35. This position actually lies in eastern Hercules, eight degrees
southwest of the brilliant blue-white zero magnitude magnitude star known as Vega (Alpha Lyrae). The radiant is best placed during
the last dark hour before dawn, when it lies highest above the horizon. At 48km/sec. the Lyrids would produce meteors of medium
velocity. Expected rates this weekend are near one per hour during the last dark hour before dawn. At maximum, hourly rate between
10-20 can be expected. Due to the northerly declination of the radiant, these meteors are not well seen from high southern
latitudes.

The team of Sirko Molau and Juergen Rendtel have a third weak radiant active at this time in the constellation of Cygnus. Video data
shows that the Nu Cygnids (NCY) are active from April 18th through May 7th. Maximum activity occurs on the morning of April 20th.
The radiant is currently located at 20:08 (302) +38. This position lies in central Cygnus, four degrees southwest of the second
magnitude star Sadr (Gamma Cygni). The radiant is best placed during the last dark hour before dawn, when it lies highest above the
horizon in a dark sky. At 42km/sec. the Nu Cygnids would produce meteors of medium velocity. Expected rates are near one per hour
during the last dark hour before dawn. Due to the northerly declination of the radiant, these meteors are not well seen from south
of the equator.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately seven sporadic meteors per hour during the last
hour before dawn as seen from rural observing sites. Evening rates would be near one 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 two per hour during the
evening hours. Locations between these two extremes would see activity between the listed figures. Evening rates are reduced due to
moonlight.

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

Pi Puppids (PPU) - 07:12 (108) -46   Velocity - 18km/sec.
Northern Hemisphere - <1 per hr. Southern Hemisphere - <1 per hr.

Sigma Leonids (SLE) - 13:16 (199) +05   Velocity - 20km/sec.
Northern Hemisphere - <1 per hr. Southern Hemisphere - <1 per hr.

h Virginids (HVR)- 14:16 (214) -11    Velocity - 24km/sec.
Northern Hemisphere - <1 per hr. Southern Hemisphere - <1 per hr.

Antihelion (ANT) - 14:40 (220) -16   Velocity - 30km/sec.
Northern Hemisphere - 1 per hr. Southern Hemisphere - 2 per hr.

Lyrids (LYR) - 18:00 (270) +35   Velocity - 48km/sec.
Northern Hemisphere - 1 per hr. Southern Hemisphere - <1 per hr.

Nu Cygnids (NCY) - 20:08 (302) +38   Velocity - 42km/sec.
Northern Hemisphere - 1 per hr. Southern Hemisphere - <1 per hr.

*For a detailed explanation on the different classes of meteor showers and other astronomical terms, please visit:
http://www.amsmeteors.org/showers.html#X2010

Clear Skies!
Robert Lunsford
American Meteor Society
 




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