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 Wednesday September 15th. At this time the moon will be located ninety degrees east of the sun and will set near 0100. This weekend the waxing crescent moon will set during the late evening hours and will not interfere with meteor observing during the prime morning hours. The estimated total hourly rates for evening observers this week is near three from the northern hemisphere and two for observers south of the equator. For morning observers the estimated total hourly rates should be near twenty from the northern hemisphere and ten as seen from the southern hemisphere. 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 this week 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 11/12. 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:
Recent video studies by Sirko Molau and Juergen Rendtel have revealed that activity from the Southern Taurids (STA) is actually detectable beginning on September 7th. So from now until December 10th, the Taurid radiants will replace the Antihelion source since they overlap and cannot be separated. The large Southern Taurid radiant is now centered at 00:32 (008) +04. This area of the sky lies on the Pisces/Cetus border, five degrees southwest of the fourth magnitude Delta Piscium. The radiant is large so that any meteor from Pisces, northern Cetus, northeastern Aquarius, or southeastern Pegasus could be a candidate for this shower. This radiant is best placed near 0200 LDT when it lies on the meridian and is located highest in the sky. Maximum activity is not until October 10th so current rates should be near three no matter your location. With an entry velocity of 29 km/sec., the average Southern Taurid meteor would be of medium-slow speed.
Studies of the IMO's vast video database by Sirko Molau and Juergen Rendtel has revealed a radiant active in Cassiopeia this time of year. The September Iota Cassiopeiids (SIC) are active from September 4th through the 13th with maximum activity occurring on the 11th. The radiant position is currently located at 02:28 (037) +66. This position lies in eastern Cassiopeia, five degrees northeast of the third magnitude star Segin (Epsilon Cassiopeiae). 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 9th. The radiant position is currently located at 03:16 (049) +41. This position lies in southwestern Perseus, only two degrees east 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 expected to be less than one per hour. With an entry velocity of 66 km/sec., most activity from this radiant would be swift. This activity is visible down to the tropical regions of the southern hemisphere. While watching for the September Epsilon Perseids I would suggest also watching for any activity from the original IMO September Perseid radiant. There have been reports of activity from this source this year including an estimated -11 fireball on September 9th. The radiant is active from a position of 04:08 (062) +47. This position is located in eastern Perseus near the fourth magnitude star Upsilon Persei. Activity is expected through September 17th.
Many radiants in the region of Eridanus have been suspected this time of year. Recent studies have verified a radiant active in Eridanus from September 3rd through the 24th with maximum activity occurring on the 6th. The Nu Eridanid (NUE) radiant is currently located at 04:40 (070) +03. This position lies in a remote region of northeastern Eridanus, a dozen degrees due south of the bright first magnitude orange star Aldebaran (Alpha Tauri). The radiant is best placed near 0500 LDT, when it lies highest above the horizon in a dark sky. Rates should be 1-2 per hour this 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.
As seen from the mid-northern hemisphere (45N) one would expect to see approximately fourteen 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 four 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 due to 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|
|Southern Taurids (STA)||Oct 10||00:32 (008) +04||29||02:00||3 - 3||II|
|September Iota Cassiopeiids (SIC)||Sep 11||02:28 (037) +66||50||05:00||<1 - <1||IV|
|September Epsilon Perseids (SPE)||Sep 09||03:16 (049) +41||66||05:00||<1 - <1||II|
|Nu Eridanids (NUE)||Sep 06||04:40 (070) +03||68||07:00||2 - 2||II|