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 Anthelion radiant will no longer be listed until the Taurid showers end in December. The Anthelion 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. Lastly, recent video data has shown that the Orionids are active all month long, even though their maximum is not until October 22nd.
During this period the moon waxes from a very thin crescent phase to nearly half-illuminated by the end of the period. This week will be the best time of the month to view meteor activity as the moon will not interfere with morning observing. The estimated total hourly meteor rates for evening observers this week is near 4 as seen from mid-northern latitudes (45N) and 3 as seen from tropical southern locations (25S). For morning observers the estimated total hourly rates should be near 18 as seen from mid-northern latitudes (45N) and 12 as seen from tropical southern locations (25S). 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. Note that the hourly rates listed below are estimates as viewed from dark sky sites away from urban light sources. Observers viewing from urban areas will see less activity as only the brightest meteors will be visible from such locations.
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.
These sources of meteoric activity are expected to be active this week.
The center of the large Anthelion (ANT) radiant is currently located at 23:36 (354) -02. This position lies in southwestern Pisces just south of the “circlet” of stars marking the western fish. These meteors may be seen all night long but the radiant is best placed near 0200 local summer time (LST) when it lies on the meridian and is positioned highest in the sky. Due to the large radiant area, meteors from this source may also appear to radiate from northeastern Aquarius and northwestern Cetus as well as Pisces. Rates at this time should be near 2 per hour no matter your location. With an entry velocity of 30 km/sec., the average Anthelion meteor would be of slow velocity.
The September Epsilon Perseids (SPE) are active from the 5th through the 28th with the peak occurring on the night of September 8/9. The radiant is currently located at 02:48 (042) +40. This position lies in southwestern Perseus, 4 degrees southwest from the famous eclipsing variable star known as Algol (Beta Persei). The radiant is best placed near 0500 LST, when it lies highest above the horizon. Rates are expected to be near 1 per hour from the northern hemisphere and less than 1 as seen from south of the equator. With an entry velocity of 65 km/sec., most activity from this radiant would be swift.
You may be surprised to see the Orionids (ORI) as an active radiant this time of year, but there is clear evidence from the IMO video database that this shower is active long before its October 22nd maximum. In fact it is in the top four most active radiants throughout September. This radiant is currently located at 04:00 (060) +03, which places it in extreme southern Taurus. The closest star of note is 4th magnitude nu Tauri, which lies 3 degrees to the north. This area of the sky is best placed in the sky during the last hour before dawn, when it lies highest above the horizon in a dark sky. Current rates would be near 1 per hour no matter your location. With an entry velocity of 67 km/sec., most activity from this radiant would be of swift speed. Note that the established radiant known as the Nu Eridanids (NUE) are actually early members of the Orionids.
The last of the Aurigids (AUR) are expected this weekend from a radiant located at 06:28 (097) +40. This position lies in eastern Auriga, 5 degrees northeast of the third magnitude star known as theta Aurigae. Rates are expected to be less than 1, no matter your location. The radiant is well placed for northern observers high in the northeastern sky during the last hour before the start of morning twilight. South of the equator, this shower is not well seen as it lies low in the northern sky during the morning hours. 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 14 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 3 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 9 per hour as seen from rural observing sites and 2 per hour during the evening hours. Locations between these two extremes would see activity between the listed figures.
The table below presents a list of radiants that are expected to be active this week. Rates and positions are exact for Saturday night/Sunday morning except where noted in the shower descriptions.
|SHOWER||DATE OF MAXIMUM ACTIVITY||CELESTIAL POSITION||ENTRY VELOCITY||CULMINATION||HOURLY RATE||CLASS|
|RA (RA in Deg.) DEC||Km/Sec||Local Summer Time||North-South|
|Anthelions (ANT)||–||23:36 (354) -02||29||02:00||2 – 2||II|
|September Epsilon Perseids (SPE)||Sep 9||02:48 (042) +40||65||03:00||1 – <1||IV|
|Orionids (ORI)||Oct 22||04:00 (060) +03||67||07:00||1 – 1||I|
|Aurigids (AUR)||Aug 31||06:28 (097) +40||67||09:00||<1 – <1||II|