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.
This week the moon will reach its full phase on Thursday September 7th. This weekend the waxing gibbous moon will set during the early morning hours allowing a small window of dark sky viewing between moonset and dawn. As the week progresses this window of opportunity shrinks until it is gone by Wednesday the 6th. The estimated total hourly rates for evening observers this week is near two 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 twenty for those in the northern hemisphere and six 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. Evening rates are reduced by the intense moonlight.
The radiant positions listed below are exact for Saturday night/Sunday morning September 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. 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 active this week:
The large Antihelion (ANT) radiant is now centered at 23:32 (353) -01. This area of the sky is centered in western Pisces, two degrees southeast of the faint star Kappa Piscium. This radiant is best placed near 0200 local daylight time (LDT) when it lies on the meridian and is 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.
The September Perseids (SPE) reach a ZHR of one on September 5 and peak four days later. The bright moon ruins the 2006 display of these meteors. Under better conditions an observer in the northern hemisphere would see 3-4 shower members per hour on September 9. The radiant is located at 03:32 (53) +46. This portion of the sky lies in central Perseus, four degrees south of the second magnitude star Mirfak (Alpha Persei). Like the Alpha Aurigids this shower is only visible from the southern tropics northward. The radiant is best placed near 0500 LDT, when it lies on the meridian. At 64km/sec.,the average September Perseid is swift.
The Alpha Aurigids (AUR) peak on the morning of September 1 with an average ZHR of ten. The actual rates fluctuate greatly from one year to the next. While nothing out of the ordinary is expected from this shower in 2006, 2007 is viewed with anticipation as a possible outburst is predicted. While the moon is favorable this year, it is not in 2007 as it will be only four days past its full phase. The radiant is located at 05:44 (86) +42, which places it in central Auriga, five degrees southeast of the brilliant zero magnitude yellow star Capella (Alpha Aurigae). Rates fall off rapidly after the date of maximum activity, rarely exceeding one shower member per hour by the 3rd. Due to the extreme northern declination, this shower is only visible from the southern tropics northward. The radiant is best placed just before the start of morning twilight, when it lies highest in a dark sky. The radiant actually culminates after sunrise. At 66km/sec., the average Alpha Aurigid is swift.
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 two random meteors can be seen per hour. Sporadic rates increase as the night progresses so rates seen near midnight would be near six per hour. Sporadic rates seen from the southern hemisphere have fallen drastically since the July maximum. One would 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 two per hour. Evening rates are reduced by the intense moonlight.