March 31, 2012
The following is a slightly edited version of Bob Lunsford’s excellent weekly summary of meteor activity. The original version can be found at the American Meteor Society’s site.
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 full phase on Friday April 6th. At that time the moon will be located opposite the sun and will be in the sky all night long. This weekend the waxing gibbous moon will set during the early morning hours, allowing a few hours of dark skies for observing before the start of morning twilight. This window of opportunity shrinks with each passing night until late in the week when the moon is near full and in the sky all night long. 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 seven as seen from mid-northern latitudes and twelve from mid-southern latitudes. 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. Even rates are reduced during this period due to moonlight.
The radiant (the area of the sky where meteors appear to shoot from) positions and rates listed below are exact for Saturday night/Sunday morning March 31/April 1. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.
The following showers are expected to be active this week:
The large Antihelion (ANT) radiant is currently located at 13:08 (204) -09. This position lies in central Virgo, four degrees northwest of the first magnitude star Spica (Alpha Virginis). Due to the large size of this radiant, Antihelion activity may also appear from the nearby constellations of Corvus, extreme eastern Hydra, southwestern Bootes, and northern Centaurus as well as Virgo. This radiant is best placed near 0200 local daylight time (LDT), when it lies on the meridian and is located highest in the sky. Rates at this time should be near two per hour no matter your location. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of slow velocity.
Studies of the IMO video database by Sirko Molau and Juergen Rendtel has revealed a weak radiant active in the constellation of Cygnus this time of year. The Zeta Cygnids (ZCY) are active from March 27 through April 13 with maximum activity occurring on April 6. The current radiant position lies at 19:52 (298) +39. This position lies in central Cygnus, six degrees west 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. Due to the northern declination of the radiant, this activity is not well seen from the southern hemisphere. No matter your location, rates at this time are expected to be less than one per hour. At 44km/sec. the Zeta Cygnids would produce meteors of average velocity.
As seen from the mid-northern hemisphere (45N) one would expect to see approximately five 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 ten 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 during this period due to moonlight.
The list below presents a condensed version of the expected activity this week.
Rates and positions are exact for Saturday night/Sunday morning.
Antihelion (ANT) – 13:08 (204) -09 Velocity 30km/sec
Northern Hemisphere – 2 per hr Southern Hemisphere – 2 per hour
Zeta Cygnids (ZCY) 19:52 (298) +39 Velocity 44km/sec
Northern Hemisphere – <1 per hr Southern Hemisphere – <1 per hour