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 reaches its first quarter phase on Monday September 1st. At this time the moon is located 90 degrees east of the sun and sets between 2300 and midnight for observers located in mid-northern latitudes. As the week progresses the moon will enter the morning sky and will begin to limit dark skies to a few hours before dawn. The estimated total hourly meteor rates for evening observers this week is near 4 as seen from the northern hemisphere and 2 as seen from southern tropical latitudes. For morning observers the estimated total hourly rates should be near 25 for observers located in mid-northern latitudes and 12 for south tropical observers. 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 during this period are reduced due to moonlight. 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 August 30/31. 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 last of the Kappa Cygnids (KCG) can be expected this weekend from a wide radiant located near 19:16 (289) +60. This location lies actually lies in southeastern Draco, 7 degrees north of the 4th magnitude star known as Kappa Cygni. Consider this position the center of a large radiant rather than a sharp point. Maximum activity was predicted to occur on August 18th, so current rates would be less than one per hour no matter your location. With an entry velocity of 23 km/sec. most of these meteors will appear to travel slower than average. The radiant is best placed near 2300 LDT (11pm LDT) when it lies nearly overhead for much of the Northern Hemisphere. Due to its high northern declination this activity is not well seen from the southern hemisphere. Despite the low rates seen from this source, this shower is known to be a producer of fireball class meteors.
The center of the large Anthelion (ANT) radiant is currently located at 23:20 (350) -03. This position lies on the Aquarius/Pisces border, 3 degrees northeast of the 4th magnitude star known as Phi Aquarii. These meteors may be seen all night long but the radiant is best placed near 0100 LDT 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 radiant from southern Pegasus, western Cetus, and western Pisces as well as Aquarius. Rates at this time should be near 2 per hour no matter you location. With an entry velocity of 30 km/sec., the average Anthelion meteor would be of slow velocity.
The last of the Theta Piscids (TPI) should be seen this weekend. This is a newly discovered radiant originally reported by SonotaCo in 2009 as the August Beta Piscids (BPI). The BPI’s have since been removed from the IAU list as researchers there feel it was a synonymous with the North Delta Aquariids, a shower no longer recognized by the IMO. Studies of the IMO video database has shown that this radiant is active between August 8 and September 1. Researchers have not been able to determine a date of maximum activity as the activity profile remains flat throughout the entire activity period. The midpoint of this source occurred on August 20. Currently the radiant should be located near 00:04 (001) +08. This position is located just west of the faint star known as Omega Piscium. This position lies close to the Anthelion and the Delta Aquariid radiants so care must be taken to distinguish between these radiants. Expected rates should be less than 1 per hour no matter your location. The radiant is best placed near 0300 LDT, when it lies highest in the sky. With an entry velocity of 39 km/sec., most activity from this radiant would be of average velocities. Visual observations of this source should be undertaken to see if it stands out from the Anthelion source or should be included as part of the Anthelions. Curiously, if one extends the radiant drift of the Southern Taurids back into August, the position of right ascension (celestial longitude) is a close match. The declination (celestial latitude) though lies too far south to be a good match.
The last of the August Gamma Cepheids (AGC) are expected this weekend. This is a new shower discovered by Željko Andreić at al. using data from the Croatian Meteor Network and SonotaCo. These meteors are active from August 22 through September 1, with maximum activity occurring on August 29th. On that date the radiant is located at 00:04 (001) +77, which places it in extreme northern Cassiopeia, 5 degrees east of the 3rd magnitude star known as Errai (Gamma Cephei). Rates at maximum should be near 1 per hour as see from the northern hemisphere. Due to the high declination of this radiant, this shower is practically invisible from the southern hemisphere. The radiant is also circumpolar (never sets) for most of the northern hemisphere and is best placed above Polaris near 0300 LDT, when it lies highest in the sky. With an entry velocity of 41 km/sec., most activity from this radiant would be of average velocities.
The last of the Delta Aquariids (SDA) should be seen this week from a radiant located at 00:32 (008) -07. This position is located in western Cetus, 4 degrees northeast of the 4th magnitude star known as Deneb Kaitos Shemali (Iota Ceti). Hourly rates have fallen to less than 1 per hour no matter your location. The radiant is best placed near 0300 LDT, when it lies highest in the sky. With an entry velocity of 39 km/sec., most activity from this radiant would be of average velocities. Some observers refer to this portion of the SDA’s as the August Iota Cetids (AIC).
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 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 04:04 (061) -02, which places it in northern Eridanus, near the Taurus border. The closest star of note is third magnitude Zaurak (Gamma Eridani), which lies ten degrees to the south. Perhaps an easier way to find the radiant would be to draw a line between Zaurak and the bright star Aldebaran (Alpha Tauri). The Orionid radiant lies approximately halfway between the two stars. 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. With an entry velocity of 67 km/sec., most activity from this radiant would be of swift speed.
Another radiant from the Perseus-Auriga complex becomes active this week from a radiant located near 04:40 (070) +43. IMO shower #149 is active from August 29-September 9, with maximum activity occurring on September 3rd. The radiant is located in eastern Perseus, directly between 0 magnitude Capella (Alpha Auriga) and 3rd magnitude Epsilon Persei. This position was once given for the September Perseids, now called the September Epsilon Perseids. The true radiant position for the September Epsilon Perseids was not revealed until an outburst of these meteors occurred in 2008, displaying a radiant further west toward Algol. This radiant is the strongest source of meteors in the sky on the mornings of September 3rd and 4th. 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. With an entry velocity of 70 km/sec., most activity from this radiant would be of swift speed.
The Aurigids (AUR) are first seen on August 29th and peak on Monday morning September 1st. On the morning of maximum activity, the radiant will be located at 06:02 (091) +39. This position lies in central Auriga, two degrees north of the third magnitude Theta Aurigae. Hourly rates will range from 3-5 in the northern hemisphere down to 0-2 in the southern hemisphere. 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 8 per hour as seen from rural observing sites and 1 per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Evening rates are reduced due to interfering moonlight.
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 Daylight Time||North-South|
|Kappa Cygnids (KCG)||Aug 18||19:16 (289) +60||23||23:00||<1 – <1||II|
|Anthelions (ANT)||–||23:20 (350) -03||29||02:00||2 – 2||II|
|Theta Piscids (TPI)||Aug 20||00:04 (001) +08||39||03:00||1 – 1||IV|
|August Gamma Cepheids (AGC)||Aug 29||00:04 (001) +77||41||03:00||1 – <1||IV|
|Delta Aquariids (SDA)||Jul 30||00:32 (008) -07||39||03:00||<1 – <1||I|
|Orionids (ORI)||Oct 22||04:04 (061) -02||67||07:00||1 – <1||I|
|IMO #149||Sep 03||04:40 (070) +43||70||08:00||2 – <1||I|
|Aurigids (AUR)||Sep 01||06:02 (091) +39||67||09:00||4 – 1||III|