Although there are no major showers active in September, meteor rates in the northern hemisphere continue to be strong. Minor activity from the constellations of Auriga, Perseus, and Taurus, as well as strong sporadic rates, produce these impressive rates. Rates as seen from the southern hemisphere have dropped off significantly since the July peak. Other than weak sporadic rates, only the antihelion radiant produces any notable shower activity in the southern skies.
The moon reaches its new phase on Friday September 22. At this time it will lie in the vicinity of the sun and will not interfere with meteor observing. Next week the moon will enter the evening sky as a waxing crescent but will set long before the prime meteor observing hours. The estimated total hourly rates for evening observers this week is near three for those north of the equator and one for those south of the equator. For morning observers the estimated total hourly rates should be near eighteen for those in the northern hemisphere and seven for those south of the equator. 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 September 23/24. 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 showers are expected to be active this week:
The large, diffuse Antihelion (ANT) radiant is now centered at 00:52 (013) +07. This area of the sky is centered in southern Pisces, two degrees south of the fourth magnitude star Delta Piscium. This radiant is above the horizon most of the night but 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 regardless of your location. With an entry velocity of 30 km/sec., the average antihelion meteor would be of medium-slow speed. Starting with next week’s report, the antihelion radiant will be replaced by the two Taurid radiants. From then through the end of November it will be impossible for the visual observer to accurately separate this activity.
The Delta Aurigids (DAU) reach peak activity in early October. Current rates have actually been a bit higher than normal with 1-2 shower members appearing each hour. The radiant is located at 05:04 (76) +49. This position lies in northwestern Auriga, three degrees northwest of the brilliant zero magnitude star Capella (Alpha Aurigae). As seen from the northern hemisphere, the radiant is above the horizon most of the night and is best placed near 0500 LDT, when it lies on the meridian. Due to the extreme northern declination of this radiant, this shower is only visible from the southern tropics northward. At 64km/sec., the average Delta Aurigid is swift.
A study of the IMO video database by Sirko Molau has shown that there is an active radiant in the constellation of Orion this time of year. This is not the well known Orionid shower, but rather a weak radiant located near Bellatrix (Gamma Orionis). This activity has been recorded from September 24-30 with peak rates near the 27th. The position of this radiant on Sunday morning is expected to be near 05:08 (77) +07 or three degrees west of the second magnitude Bellatrix. This area of the sky is above the horizon most of the night and is best placed near 0500 LDT, when it lies on the meridian. With the radiant lying just north of the celestial equator, this shower would be visible over most of the Earth. Meteors from this radiant strike the Earth with a velocity of 59km/sec. This would produce mostly swift meteors.
Sporadic rates continue to climb slowly for observers located in the northern hemisphere. One would expect to see perhaps fourteen random meteors during the last hour before dawn from rural observing sites. During the first dark hour after the end of evening twilight, perhaps three random meteors can be seen per hour. Sporadic rates increase as the night progresses so rates seen near midnight would be near eight per hour. Sporadic rates seen from the southern hemisphere have reached their annual minimum. One would expect to see approximately four random meteors per hour during the last hour before dawn and one per hour during the first dark hour after the end of evening twilight. Rates near midnight would be near three per hour.