Meteor Activity Outlook for March 12-18, 2011

During this period the moon reaches its first quarter phase on Saturday March 12. At this time the half illuminated moon will be in the sky from dusk through midnight local standard time (0100 local daylight saving time). As the week progresses the waxing moon will become gibbous shaped and will set later and later, remaining in the sky nearly the entire night toward the end of the week. The estimated total hourly rates for evening observers this week is near two as seen from the northern hemisphere and three as seen from the southern hemisphere. For morning observers the estimated total hourly rates should be near ten from the northern hemisphere and fourteen as seen from south of the equator. 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. Rates are reduced for the evening hours 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 5/6. 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 12:20 (185) -04. This area of the sky lies in western Virgo, three degrees south of the fourth magnitude star Zaniah (Eta Virginis). This radiant is best placed near 0200 local daylight saving 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 eastern Leo, southern Coma Berenices, Sextans, Crater, Corvus, or Virgo could be a candidate for this shower. 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 medium-slow speed.

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. The maximum activity is predicted for the morning of March 14th. 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 16:32 (248) -51. This position lies in central Norma, two degrees southeast 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.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately eight 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 two per hour during the evening hours. Locations between these two extremes would see activity between the listed figures.

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

SHOWER DATE OF MAXIMUM ACTIVITY CELESTIAL POSITION ENTRY VELOCITY CULMINATION HOURLY RATE CLASS*
RA (RA in Deg.) DEC Km/Sec Local Standard Time North-South
Antihelion (ANT) - 12:20 (185) -04 30 0100 2 - 2 II
Gamma Normids (GNO) Mar 14 16:32 (248) -51 56 05:00 1-<1 IV