(meteorobs) Meteor Activity Outlook for May 1-7, 2010

Fri Apr 30 00:36:17 EDT 2010

May is a fairly slow month for meteor activity. The Eta Aquariids are very active the first two weeks of the month then fade as the 
month progresses. The only other showers active this month are the weak Nu Cygnids, the Eta Lyrids, and the Antihelion radiant. 
These will add only 1-2 meteors per hour to the total count. 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) continue to rise this month toward a maximum in July.

During this period the moon reaches its last quarter phase on Wednesday 6th. At this time the moon lies ninety degrees west of the 
sun and rises near 0100 local daylight time (LDT). This weekend the waning gibbous moon will rise during the late evening hours, 
effectively ruining your chance of seeing good meteor activity the remainder of the night. Conditions improve slightly with each 
passing night as the moon's phase lessens and it rises later and later. 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 seven from the northern hemisphere and twelve 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. Morning rates are reduced due to moonlight.

The radiant positions and rates listed below are exact for Saturday night/Sunday morning May 1/2. 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 15:36 (234) -19. This area of the sky lies in eastern Libra, seven degrees 
northwest of the second magnitude star Dschubba (Delta Scorpii). This radiant is best placed near 0200 local daylight time (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 
extreme eastern Hydra, Libra, northern Lupus, or western Scorpius 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 team of Sirko Molau and Juergen Rendtel have discovered a 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 occurred on the morning of April 
20th. The radiant is currently located at 21:48 (327) +48. This position lies in northeastern Cygnus close to the faint star known 
as Pi 2 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 less than one per hour. Due to the 
northerly declination of the radiant, these meteors are not well seen from south of the equator.

The Eta Aquariids (ETA) are particles from Halley's Comet, produced in Earth-crossing orbits many centuries ago. We pass closest to 
these orbits from May 5 through the 9th. During this period the Eta Aquariids are at their best, capable of producing ZHR's of 
sixty. The actual visible rates are most often less than half this figure due to the low altitude of the radiant at dawn. Observed 
hourly rates at maximum normally vary from zero at 60 degrees north latitude to 25 near the equator and back down to near zero again 
in Antarctica, where the radiant elevation is very low. Hourly rates this weekend are anywhere from zero to five per hour depending 
on your latitude and observing conditions. Rates will increase significantly as the week progresses as we approach the May 7 
maximum. The radiant is currently located at 22:24 (336) -02. This area of the sky is located in northern Aquarius, just south of 
the fourth magnitude star Gamma 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. No matter your location these meteors will appear from the eastern sky and shoot in all 
directions. If the radiant has sufficient altitude Eta Aquariid meteors can also be seen shooting down toward the eastern horizon. 
With an entry velocity of 67 kilometers per second, a majority of these meteors will appear to move swiftly with a high percentage 
of the bright meteors leaving persistent trains. Surprisingly, this shower produces very few fireballs.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately four 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 seven 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. Morning 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.

Antihelion (ANT) - 15:36 (234) -19   Velocity - 30km/sec.
Northern Hemisphere - 1 per hr. Southern Hemisphere - 2 per hr.

Nu Cygnids (NCY) - 21:48 (327) +48 Velocity - 42km/sec.
Northern Hemisphere - <1 per hr. Southern Hemisphere - <1 per hr.

Eta Aquariids (ETA) - 22:24 (336) -02   Velocity - 67km/sec.
Northern Hemisphere - 2 per hr. Southern Hemisphere - 3 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 