Meteor Activity Outlook for August 29-September 4, 2009

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. During the second half 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 second half 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 full phase on Friday September 4th. At that time the moon will rise at sunset and will be in the sky the entire night. This weekend, the waxing gibbous moon will set during the early morning hours allowing a few hours of dark skies before the start of morning twilight. This window of opportunity will lessen each night as the week progresses. The estimated total hourly rates for evening observers this week is near three as seen from the northern hemisphere and two from the southern hemisphere. For morning observers the estimated total hourly rates should be near sixteen from the northern hemisphere and eight as seen from the southern hemisphere. 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 are reduced by moonlight.

The radiant positions and rates listed below are exact for Saturday night/Sunday morning August 29/30. 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:

The large Antihelion (ANT) radiant is now centered at 23:16 (349) -03. This area of the sky lies on the Pisces/Aquarius border, two 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. Rates at this time should be near two 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 September 1st. The redefined radiant, obtained from recent video data and the 2007 outburst, is located near 06:06 (091.5) +39. This position is located in eastern Auriga, two degrees north of the third magnitude star Theta Aurigae. The radiant is best placed during the last dark hour before morning twilight when it lies highest in the sky. Hourly rates on Tuesday morning are expected to be near five. At 65 km/sec., these meteors are swift, often exhibiting persistent trains.

As seen from the mid-northern hemisphere (45N) the Sporadic rates are becoming more active. One would expect to see approximately thirteen random meteors during the last hour before dawn from rural observing sites and two per hour during the evening hours. As seen from the mid-southern hemisphere (45S) morning rates would be near six per hour as seen from rural observing sites and one per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Evening rates are reduced by moonlight.

The table below presents a summary of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning August 29/30, but may be used all week.