Meteor Activity Outlook for August 31-September 6, 2007

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 is impossible to seperate. Therefore the antihelion radiant will be excluded from the list 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 last quarter phase on Tuesday September 4. At this time the half illuminated moon is located ninety degrees west of the sun and rises near 0100 local daylight time. The estimated total hourly rates for evening observers this week is near four for those located north of the equator and one for observers south of the equator. For morning observers the estimated total hourly rates should be near ten for those located in the northern hemisphere and five for those viewing from south of the equator. 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. Morning rates are reduced by moonlight.

The radiant positions and rates listed below are exact for Saturday night/Sunday morning September 1/2. 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 the IMO's video database has led to the discovery of an active radiant in Ursa Minor this week. The shower peaks on September 1 from a radiant located at 17:24 (261) +83. This position lies in the handle of the Little Dipper just west of the fourth magnitude star Epsilon Ursae Minoris. The radiant is best placed near 2000 (8pm) local daylight time, when it lies highest in the sky. Current rates would mostly likely be less than one per hour, but this is uncertain. With an entry velocity of 38km/sec., activity from this radiant would be of medium velocity.

The Antihelion (ANT) radiant is now centered at 23:28 (352) -02. This area of the sky is located in a western Pisces, three degrees south of the faint star Kappa Piscium. This radiant is best placed near 0200 LDT, when it lies on the meridian and is 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 antihelion meteor would be of medium-slow speed.

The Alpha Aurigids (AUR) are predicted to reach maximum activity at 11:37 Universal Time on September 1. This timing favors western North America and the eastern pacific area including Hawaii. Other areas are expected to see little from this radiant. The radiant position is usually located near 05:36 (084) +42, which is located in central Auriga, five degrees southeast of the brilliant zero magnitude yellow star Capella (Alpha Aurigae). Near the time of maximum the radiant may be slightly different from this position but the swift meteors from Auriga will be easy to differenciate from other activity that night. This radiant is circimpolar 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. At 66 km/sec., these meteors are swift, often exhibiting persistent trains. The moon will be a major factor on September 1, obscuring the faint meteors. Finding dry, transparent skies and facing away from the moon will be the best way overcome the lunar glare.

Sirko Molau's study of the IMO's video database has led to the discovery of an active radiant in eastern Auriga this week. The shower peaks on September 1 from a radiant located at 07:24 (111) +39. This position lies six degrees northwest of the second magnitude star Castor (Alpha Geminorum). The radiant is best placed just before dawn when it lies highest in a dark sky. Current rates would mostly likely be less than one per hour, but this is uncertain. With an entry velocity of 39km/sec., most activity from this radiant would be of medium velocities.

Sporadic rates are slowly rising for observers in the northern hemisphere and falling steadily for those located south of the equator. One would expect to see perhaps seven random meteors during the last hour before dawn from rural observing sites in the northern hemisphere. During the first dark hour after the end of evening twilight, perhaps four random meteors can be seen per hour. As seen from the southern hemisphere late morning rates would now be near three per hour. During the first dark hour after the end of evening twilight, perhaps two random meteors can be seen per hour. Morning rates are reduced by moonlight.