September offers longer nights in the northern hemisphere that tend to be less hazy than those experienced in mid-summer. In the sky, no major showers are visible from either hemisphere but the northern hemisphere enjoys the advantage of higher sporadic rates. Most of the shower activity this month is produced from the Perseus-Aurigid complex active this time of year. These showers rarely produce more than five meteors per hour but still manage to produce most of the shower activity seen this month. Unfortunately the Perseus-Aurigid complex lies too low in the northern sky for southern hemisphere observers to view very well. Video studies have shown that the Southern Taurids are visible as early as September 7th therefore after this date the Antihelion radiant will no longer be listed until the Taurid showers end in December. The Antihelion meteors are still active but their radiant is superimposed upon that of the more numerous Taurids, therefore it is impossible to properly separate these meteors. Observers in the southern hemisphere suffer from some of their lowest rates of the year this month. The Southern Taurid radiant is not too badly placed so observers south can expect to see a little of this activity this month.
During this period the moon reaches its first quarter phase on Sunday September 4th. At this time the moon will lie ninety degrees east of the sun and will set near midnight local daylight time (LDT) as seen from mid-northern latitudes. Next week the waxing gibbous moon will set later during the morning hours but still allowing meteor observers a window of opportunity to view under dark conditions between moon set and the start of morning twilight . The estimated total hourly rates for evening observers this week is near three as seen from the northern hemisphere and two as seen from the southern hemisphere. For morning observers the estimated total hourly rates should be near fifteen as seen from mid-northern latitudes and eight 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. Evening rates are reduced 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 September 3/4. 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 23:36 (354) -01. This area of the sky lies in western Pisces, just below the faint circle of stars known as the “circlet”. This radiant is best placed near 0200 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 Aquarius, western Pisces, northwestern Cetus, or southern Pegasus could be a candidate for this shower. Rates at this time should be near one per hour no matter your location. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of medium-slow speed.
Studies of the IMO’s video database by Sirko Molau and Juergen Rendtel has revealed a new radiant active in Perseus this time of year. The September Iota Cassiopeiids (SIC) are active from September 4th through the 13th with maximum activity occurring on the 12th. The radiant position is currently located at 02:33 (038) +57. This position lies just over the border of Cassiopeia in Perseus, four degrees northeast of the fourth magnitude star Eta Persei. The radiant is best placed near 0500 LDT, when it lies highest above the horizon. Rates throughout the activity period are expected to remain less than one per hour. With an entry velocity of 50 km/sec., most activity from this radiant would be swift. Due to the high northern declination (celestial latitude) meteors from this shower are not well seen from the southern hemisphere.
The September Epsilon Perseids (SPE) are active from September 5th through the 13th with maximum activity occurring on the 10th. The radiant position is currently located at 02:56 (044) +41. This position lies in southwestern Perseus, only two degrees west of the famous eclipsing variable star known as Algol (Beta Persei). The radiant is also best placed near 0500 LDT, when it lies highest above the horizon. Rates are currently less than one per hour but will increase to 1-3 per hour at maximum. This shower experienced an outburst in 2008 with ZHR’s near 25 for a short time. Many bright meteors were produced during this outburst with the brightest estimated at magnitude -8. With an entry velocity of 66 km/sec., most activity from this radiant would be swift. This activity is visible from the tropical regions of the southern hemisphere, but further south the radiant becomes too low in the sky to produce much activity.
Many radiants in the region of Eridanus have been suspected this time of year. Recent studies of the IMO’s video database by Sirko Molau and Juergen Rendtel has verified a radiant active in Eridanus from September 3rd through the 24th with maximum activity occurring on the 7th. The Nu Eridanid (NUE) radiant is currently located at 04:20 (065) -01. This position lies in a remote region of northeastern Eridanus. The nearest bright star is Rigel (Beta Orionis), which lies twelve degrees to the southeast. The radiant is best placed during the last hour before the start of morning twilight. Rates may be close to two per hour this weekend and early next week. With an entry velocity of 68 km/sec., most activity from this radiant would be swift. With the radiant lying close to the celestial equator, these meteors are seen equally well from both hemispheres.
The last of the Aurigids (AUR) can be seen this weekend from a radiant located at 06:21 (095) +40. This position lies in central Auriga, two degrees northeast of the third magnitude Theta Aurigae. The radiant is best placed during the last hour before the start of morning twilight when it lies highest in a dark sky. Hourly rates this weekend will be very low, less than one per hour no matter your location.Â With an entry velocity of 67 km/sec., most activity from this radiant would be swift.
As seen from the mid-northern hemisphere (45N) one would expect to see approximately twelve 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 five per hour as seen from rural observing sites and one per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Evening rates are reduced by moonlight.
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)||–||23:36 (354) -01||23||22:00||1 – 1||II|
|September Iota Cassiopeiids (SIC)||Sep 12||02:33 (038) +57||50||05:00||<1 – <1||IV|
|September Epsilon Perseids (SPE)||Sep 10||02:56 (044) +41||66||05:00||<1 – <1||II|
|Nu Eridanids (NUE)||Sep 07||04:20 (065) -01||68||07:00||2 – 2||IV|
|Aurigids (AUR)||Sep 01||06:21 (095) +40||67||09:00||<1 – <1||II|