(meteorobs) Meteor Activity Outlook for March 2-8, 2013

[Robert Lunsford]

As seen from the northern hemisphere, March is the slowest month for meteor activity. No major annual showers are active and only a few 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 Antapex 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 last quarter phase on Monday March 4th. At this time the moon is located ninety degrees west of the sun and rises near midnight local standard time (LST) as seen from mid-northern latitudes. This weekend the slightly gibbous moon will be a major nuisance unless you have extremely transparent skies which will allow you to see faint meteors. As the week progresses the waning crescent moon will rise later each morning, allowing a little more viewing time under dark skies. The estimated total hourly meteor rates for evening observers this week is near two as seen from the northern hemisphere and four as seen from south of the equator. For morning observers the estimated total hourly rates should be near six from the mid-northern hemisphere and thirteen from the mid-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 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 2/3. 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 large Anthelion (ANT) radiant is currently centered at 11:40 (175) +01. This position lies in western Virgo, two degrees west of the fourth magnitude star Zavijava (Beta Virginis). These meteors may be seen all night long but the radiant is best placed near 0100 LST when it lies on the meridian and is 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) are active from a radiant located at 15:12 (228) -51. This position lies in southeastern Lupus, two degrees north of the third magnitude star Zeta Lupi.  Due to the southerly declination (celestial latitude) these meteors cannot be seen north of the northern tropical regions. They are best seen from mid-southern latitudes where the radiant lies high in the sky near 0500 local summer time. This shower peaks on March 13 so current hourly rates would less than one no matter you location. At 56km/sec. the Gamma Normids would produce mostly swift meteors.

IMO shower #37 is active Tuesday March 5th through March 10th. Maximum activity is expected on the 5th from a radiant located at 15:43 (236) +42. This position is located in a extreme northeastern Bootes. The closest bright star is second magnitude Alphecca (Alpha Coronae Borealis), which lies fifteen degrees to the southwest. These meteors are best seen near during the last dark hour before dawn when the radiant lies highest above the horizon in a dark sky. Rates would mostly likely be less than one shower member per hour, no matter your location. Observers in the northern hemisphere have an advantage in that the radiant lies higher in the sky during the morning hours. At 42 km/sec. these meteors would have a medium velocity.

IMO shower #35 is active through Tuesday from a radiant located at 16:39 (250) +49. This position is located in a remote area of northwestern Hercules. The closest bright star is Eltanin (Gamma Draconis), which lies twenty degrees to the east.  Peak activity is expected on the morning of March 4th. These meteors are best seen near during the last dark hour before dawn when the radiant lies highest above the horizon in a dark sky. Rates would mostly likely be less than one shower member per hour, no matter your location. Observers in the northern hemisphere have an advantage in that the radiant lies higher in the sky during the morning hours. At 40 km/sec. these meteors would have a medium velocity.

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 eleven 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. Rates are reduced during the morning hours 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 .

Anthelions (ANT) - 11:40 (175) +01   Velocity - 30km/sec.
Northern Hemisphere - 2 per hr. Southern Hemisphere - 2 per hr

Gamma Normids (GNO) - 15:12 (228) -51   Velocity - 56km/sec.
Northern Hemisphere - <1 per hr. Southern Hemisphere - <1 per hr

IMO #37 - 15:43 (236) +42   Velocity - 42km/sec.
Northern Hemisphere - <1 per hr. Southern Hemisphere - <1 per hr

IMO #35 - 16:39 (250) +49 Velocity - 40km/sec.
Northern Hemisphere - <1 per hr. Southern Hemisphere - <1 per hr

Clear Skies!
Robert Lunsford
American Meteor Society