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. 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 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 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 Daylight Time||North-South|
|Antihelions (ANT)||–||12:40 (190) -05||30||02:00||2 – 2||II|
|Gamma Normids (GNO)||Mar 13||16:56 (254) -51||56||06:00||<1 – 1||IV|
|Zeta Serpentids (ZSE)||Mar 24||17:04 (256) -04||64||06:00||<1 – <1||IV|