Meteor Activity Outlook for March 17-23, 2012
March 18, 2012 2 Comments
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.
As seen from the northern hemisphere, March is the slowest month for meteor activity. No major annual showers are active and only two very weak minor showers produce activity this month. The sporadic rates are also near their annual minimum so there is not much to look forward to this month except for the evening fireballs that seem to peak this time of year from the northern hemisphere. This could be due to the fact the Antiapex radiant lies highest above the horizon this time of year during the evening hours. From the southern hemisphere, activity from the Centaurid complex begins to wane with only the weak activity visible from Norma and perhaps others areas nearby. At least southern sporadic rates are still strong to make the late summer viewing a bit more pleasurable.
During this period the moon reaches its new phase on Thursday March 22th. At that time the moon will be located near the sun and will not be visible at night. This weekend the waning crescent moon will rise during the early morning hours but will not interfere with meteor observations. The estimated total hourly rates for evening observers this week is near three for observers in the northern hemisphere and four 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 thirteen 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.
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 17/18. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.
The large Antihelion (ANT) radiant is currently located at 12:40 (190) -05. This position lies in western Virgo, only three degrees south of the famous third magnitude double star Porrima (Gamma Virginis). Due to the large size of this radiant, Antihelion activity may also appear from the nearby constellations of Crater, Corvus, and eastern Leo 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.
The Gamma Normids (GNO) is a weak shower best seen from the southern hemisphere. This shower is only visible south of forty degrees north latitude. The further one is located south (down to 50S) the better the radiant is situated in the sky. Expected rates from the southern hemisphere is currently near one per hour, even with the radiant located high in the sky. The current radiant position lies at 16:56 (254) -51. This position lies in central Norma, three degrees southwest of the fourth magnitude star Gamma Normae. The radiant is best placed during the last dark hour before dawn, when it lies highest above the horizon in a dark sky. At 56km/sec. the Gamma Normids would produce mostly swift meteors.
On Thursday morning, March 22, activity from the Zeta Serpentids (ZSE) may begin to be noticed. This shower is active on only five mornings with peak activity occurring on the 24th. Rates would likely be less than one shower member per hour, even at maximum activity. The radiant is located near 17:05 (256) -04. The area of the sky is located in a blank portion of central Ophiuchus, some eight degrees northeast of third magnitude Zeta Ophiuchi. The radiant is best placed during the last dark hour before dawn, when it lies highest above the horizon in a dark sky. At 64km/sec. the Zeta Serpentids would produce mostly swift meteors.
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 two 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 three per hour during the evening hours. Locations between these two extremes would see activity between the listed figures.
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) – 12:40 (190) -05 Velocity 30km/sec
Northern Hemisphere – 2 per hr Southern Hemisphere – 2 per hour
Gamma Normids (GNO) 16:56 (254) -51 Velocity 56km/sec
Northern Hemisphere – <1 per hr Southern Hemisphere – 1 per hour
Zeta Serpentids (ZSE) 17:04 (256) -04 Velocity 64km/sec
Northern Hemisphere – <1 per hr Southern Hemisphere – <1 per hour