(meteorobs) Meteor Activity Outlook for August 31-September 6, 2013

[Robert Lunsford]

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 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 new phase on Thursday September 5th. At this time the moon is located near the sun and will not be visible at night. This weekend the waning crescent moon will not rise until the early morning hours, leaving a majority of the night in total darkness. Even with the moon above the horizon for an hour or two before dawn, it will be so thin that it will not interfere much with observing. The estimated total hourly meteor rates for evening observers this week is near five for observers located in the northern hemisphere and three for those viewing south of the equator. For morning observers the estimated total hourly rates should be near twenty as seen from mid-northern latitudes and near eleven for observers viewing from tropical 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.  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  31/September 1. 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 sources of meteoric activity are expected to be active this week:

The center of the large Anthelion (ANT) radiant is currently located at 23:24 (351) -02. This position lies in western Pisces, just below the "Circlet", a group of six faint stars forming a circle. Due to the large, oval-shaped radiant, activity from this source may also be seen coming from eastern Aquarius, northwestern Cetus, southern Pegasus as well as Pisces. These meteors may be seen all night long but the radiant is best placed near 0200 local daylight time (LDT) when it lies on the meridian and is located 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 Anthelion meteor would be of slow velocity.

There is an new unnamed source of meteors active this week from a radiant located at 00:36 (009) +78. IMO shower #141 is active from August 26-September 3, with maximum activity occurring on August 29. The radiant is located in northern Cepheus, a few degrees northeast of the third magnitude star known as Errai (Gamma Cephei). This area of the sky is best placed in the sky near 0300 LDT, when it lies highest above the horizon in a dark sky. With an entry velocity of 59 km/sec., most activity from this radiant would be of swift speed.

New data for the September Epsilon Perseids (SPE) shows that this radiant is active from September 1st through the 28th with maximum activity occurring on the 9th. The radiant position is currently located at 02:52 (043) +41. This position lies in southwestern Perseus, only three degrees west of the famous eclipsing variable star known as Algol (Beta Persei). The radiant is best placed near 0500 LDT, when it lies highest above the horizon. Rates are currently less than one per hour but will increase to near 3 per hour at maximum. Commencing on September 5th, this radiant will become the strongest source of activity in the sky and will remain so throughout most of the month. 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.

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) -01, 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 new, unnamed source of meteors active this week from a radiant located at 04:20 (065) +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, three degrees northeast of the third magnitude star known as 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 Sunday 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 fourteen sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near four per hour. As seen from the tropical southern latitudes (25S), morning rates would also be near seven per hour as seen from rural observing sites and two 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.

Anthelions (ANT) - 23:24 (351) -02   Velocity - 30km/sec. 
Northern Hemisphere - 1 per hr.   Southern Hemisphere - 1 per hr 
 
IMO #141 - 00:36 (009) +78   Velocity - 43km/sec. 
Northern Hemisphere - <1 per hr. Southern Hemisphere - <1 per hr 

September Epsilon Perseids (SPE) - 02:52 (043) +41   Velocity - 66km/sec. 
Northern Hemisphere - <1 per hr. Southern Hemisphere - <1 per hr 

Orionids (ORI) - 04:04 (061) -01   Velocity - 67km/sec. 
Northern Hemisphere - 1 per hr.  Southern Hemisphere - 1 per hr 
 
IMO #149 - 04:20 (065) +43   Velocity - 70km/sec. 
Northern Hemisphere - 2 per hr. Southern Hemisphere - 1 per hr 
 
Aurigids (AUR) 06:02 (091) +39   Velocity - 67km/sec. 
Northern Hemisphere - 3 per hr.  Southern Hemisphere - 1 per hr 
 
Clear Skies! 
Robert Lunsford 	 
American Meteor Society