By Robert Lunsford - American Meteor Society
Mar 11, 2005, 09:55

     


This upcoming period will see the moon reaching its first quarter phase on Thursday March 17.  At this time the moon will set near midnight, allowing morning observers a dark sky in which to view the sparse activity. This weekend will have a waxing crescent moon that will set early in the evening, allowing an even better opportunity to view the March meteor activity.

The estimated total hourly rates for evening observers this week should be near two for those in the Northern Hemisphere and three for those observers south of the equator. For morning observers the estimated total hourly rates should be near seven for those located in the Northern Hemisphere and twelve for those in the Southern Hemisphere. These rates assume that you are watching from rural areas away from all sources of light pollution.

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 positions listed below are exact for Saturday night/Sunday morning March 12/13. 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.

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.

These are the showers that may be observed this week:

The Anthelion radiant is now centered at 12:24 (186) -02. This area of the sky is located in western Virgo, four degrees southwest of the third magnitude star Porrima (Gamma Virginis). Since this radiant is large and diffuse, any slow to medium speed meteor from northeastern Crater, Virgo or Corvus could be a candidate for this shower. The center of this area is best placed near 0100 local standard time when it lies on the meridian and is highest in the sky. At this time expect to see two shower members per hour no matter your location.

Unlike most of the annual showers the antihelion source is produced by debris from unknown objects orbiting in a direct motion like the earth.

These objects are most likely asteroids, which produce stony and metallic debris whose density is much greater than material produced by comets. There is also the possibility that some of this activity may be caused by the "Jupiter family of comets", comets which have been altered by Jupiter's gravity into much shorter orbits. This material collides with the earth on the inbound portion of its orbit, before its closest approach to the sun.

Therefore we best see them just after midnight when we are facing the direction from which this activity appears. The antihelion source is active all year from an area of the sky nearly opposite that of the sun. The center of this source will move approximately one degree eastward per day and travels through many different constellations over the course of a year. It may make sense to list these meteors as anthelions or "ANT" but a majority of meteor organizations prefer that you list them from the constellation in which the radiant is currently located or the constellation where the shower reaches maximum activity. Observers who send their reports to the International Meteor Organization (I.M.O.) should label these meteors as Virginids (VIR).

The Gamma Normids (GNO) are active from a radiant located at 16:32 (248) -51. This position lies in eastern Norma, two degrees east of the fourth magnitude star Gamma Normae. ZHR's are near six at maximum (March 13). Due to the far southern declination of the radiant, this shower is not well seen north of the northern equatorial regions. This area of the sky is best placed near 0600 local standard time when it lies highest in the sky.

At 56 km/sec. the Gamma Normids normally produce meteors of swift angular velocities.

The Delta Pavonids (DPA) are listed among the radiants of the Dutch Meteor Society. They are predicted to peak on March 29. The radiant currently lies at 18:48 (282) -60. This area of the sky is located in a sparse area of western Pavo, some twenty five degrees southwest of the second magnitude star Peacock (Alpha Pavonis). This area of the sky is too far south to be seen north of the northern equatorial areas. The rate at maximum is five shower members per hour. These rates are rarely seen except from far southern locations such as Australia, South Africa and southern South America. Current hourly rates would be less than one. The best time to view this activity is just before the start of morning twilight, when the radiant lies highest in a dark sky. With an entry velocity of 60 kilometers per second, a majority of these meteors will appear to move swiftly.

The Sporadic rates for the Northern Hemisphere are now reaching their low plateau for the year. From now through June morning sporadic rates will remain near five per hour. During the evening hours perhaps two random meteors can be seen per hour. Sporadic rates seen from the Southern Hemisphere are slowing increasing toward a July maximum. From south of the equator one would expect to see approximately eight random meteors per hour during the late morning hours and three per hour during the evening.