The American Meteor Society

Meteor Activity Outlook for 
  August 30-September 5, 2008

By Robert Lunsford 
AMS Operations Manager

September offers longer nights and cooler temperatures in the northern hemisphere. In the sky, no major showers are visible from either hemisphere but the northern hemisphere enjoys the advantage of higher sporadic rates. The two recognized minor showers active in early September have high northern declinations (celestial latitude) therefore are much better suited to be viewed from locations north of the equator. Toward the end of the month the antihelion radiant becomes entangled with the two Taurid radiants and it is impossible to separate them. Therefore the antihelion radiant will be excluded from the list from the last week of September until the end of the Taurid activity period late in November. Observers in the southern hemisphere suffer from some of their lowest rates of the year this month. The Taurid radiants are not too badly placed so observers south of the equator can expect to see a little of this activity toward the end of the month.

During this period the moon reaches its new phase on Saturday August 30. At this time the moon will rise and set with the sun and will not be visible at night. As the week progresses the waxing crescent moon will enter the evening sky but will set during the early evening hours allowing observers to view in dark skies the remainder of the night. The estimated total hourly rates for evening observers this week is near three for those located in the mid-northern hemisphere (45 N) and two for those viewing from the mid-southern hemisphere (45 S). For morning observers the estimated total hourly rates should be near eighteen for those located in the mid-northern hemisphere (45 N) and ten for those viewing from the mid-southern hemisphere (45 S). These rates assume that you are watching from rural areas away from all sources of light pollution. 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.

The radiant 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.

The following showers are expected to be active this week:

Sirko Molau's study of video radiants has shown an active radiant located in Ursa Minor during this period. The September Ursid Minorids (SUM) peak on September 1st with a radiant located near 17:24 (261) +83. The area of the sky is located in central Ursa Minor not far from Polaris, the North Star. This radiant is circumpolar for areas north of 7 degrees north latitude. Interestingly enough, just 14 degrees further south at 7 degrees south latitude, it cannot be seen at all! It reaches its highest altitude above the horizon near 1900 (7pm) LDT. Most locations in the northern hemisphere are not dark until an hour or two later so the period just as dusk settles in would be the best time to try and observe this activity. Hourly rates would most likely be less than one. With an entry velocity of 38 km/sec., most members of the September Ursid Minorids would possess a medium velocity.

Another entry in Sirko Molau's study of video radiants is located in Draco during this period. The August Draconid (AUD) radiant lies near 19:28 (292) +65, which is half-way between the bright stars Kochab (Beta Ursae Minoris and Deneb (Alpha Cygni). This radiant is circumpolar for locations north of 25 degrees north latitude. It reaches its highest altitude above the horizon near 2200 LDT, therefore is best seen during the evening hours. Maximum activity occurred on August 27. Hourly rates this weekend would most likely be less than one. The northern hemisphere is heavily favored for viewing this activity. With an entry velocity of 30 km/sec., most members of the August Draconids would possess a medium-slow velocity. It should be noted that if the Kappa Cygnid period is extended past August 25, the radiant drift would be similar to the August Draconids.

The large Antihelion (ANT) radiant is now centered at 23:20 (350) -03. This area of the sky lies on the Pisces/Aquarius border, three degrees northeast of the fourth magnitude Phi Aquarii. Actually, the radiant is so large that any meteor from northeastern Aquarius, western Pisces, or southwestern Pegasus could be a candidate for this shower. This radiant is best placed near 0200 LDT when it lies on the meridian and is highest in the sky. Hourly rates at this time should be near three no matter your location. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of medium-slow speed.

The Aurigids (AUR) reach maximum activity on the morning of August 31st. The radiant is located near 05:36 (084) +42. This position is located in central Auriga, four degrees southeast of the brilliant zero magnitude yellow star Capella (Alpha Aurigae). This radiant is circumpolar north of 48 degrees north latitude. For areas further south in the northern hemisphere, the radiant rises during the late evening hours. From south of the equator the radiant will rise during the late morning hours (if at all) depending on your southern latitude. Regardless of location the radiant is best placed during the last dark hour before morning twilight when it lies highest in the sky. Hourly rates on Monday morning are expected to be near five. Unlike last year, no outburst is expected from this shower. At 66 km/sec., these meteors are swift, often exhibiting persistent trains.

The Southern September Lyncid (SSL) is another shower discovered by Sirko Molau in his study of video radiants. This shower is active from August 28th through September 5th and peaks on the morning of September 1st. The radiant actually lies in extreme eastern Auriga, just over the border from Lynx. This position also lies six degrees north of the famous double star Castor (Alpha Geminorum). The radiant rises near 0100 LDT and reaches its highest altitude above the horizon near 0900 LDT. Since this is during daylight hours the best time to view activity from the Southern September Lyncids would be during the last dark hour before dawn. The much stronger Aurigids are active the same night and care must be taken to avoid confusing the two showers. Both showers produce swift meteors but the Aurigids would be far more numerous. If any observer is serious about seeing any of this activity they should include both radiants within their field of view. Viewing toward the north would also allow the monitoring of the September Ursa Minorids. With an entry velocity of 52km/sec., most members of the Southern September Lyncids would move swiftly

As seen from the mid-northern hemisphere (45N) one would expect to see approximately thirteen Sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near three per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near six 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 summary of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning but may be used all week.

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
September Ursid Minorids (SUM)	Sep 01	17:24 (261) +83	38	19:00	<1 - <1	IV
August Draconids (AUD)	Aug 27	19:28 (292) +65	30	22:00	<1 - <1	IV
Antihelion (ANT)	-	23:20 (350) -03	30	02:00	3 – 3	II
Aurigids (AUR)	Aug 31	05:36 (084) +42	66	07:00	2 - <1	I
Southern September Lyncid (SSL)	Sep 01	07:24 (111) +39	52	09:00	<1 - <1	I

*For a detailed explanation on the different classes of meteor showers and other astronomical terms, please visit: http://www.amsmeteors.org/showers.html#X2008

Last updated: August 30, 2008 at 0300 UT