Meteor Activity Outlook for September 12-18, 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 last quarter phase on Saturday the 12th. At this time the moon will rise near 0100 LDT (Local Daylight Time) and will remain in the sky the rest of the night. This will create some lunar interference which can be easily overcome by observing with the moon at your back. As the week progresses the moon wanes and rises later each morning. Thus conditions improve with each passing night. The estimated total hourly rates for evening observers this week is near four as seen from the northern hemisphere and three from the southern hemisphere. For morning observers the estimated total hourly rates should be near sixteen from the northern hemisphere and seven 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. Morning rates are reduced by moonlight this week.

The radiant positions and rates listed below are exact for Saturday night/Sunday morning September 12/13. 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:

Recent video studies by Sirko Molau have revealed that activity from the Southern Taurids (STA) is actually detectable beginning on September 7th. So for now until December 10th, the Taurid radiants will replace the Antihelion source since they overlap. The large Southern Taurid radiant is now centered at 00:38 (010) +04. This area of the sky lies on the Pisces/Cetus border, five degrees southwest of the fourth magnitude Delta Piscium. The radiant is large so that any meteor from Pisces, northern Cetus, northeastern Aquarius, 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 located highest in the sky. Maximum activity is not until October 10th so current rates should be near three no matter your location. With an entry velocity of 29 km/sec., the average Southern Taurid meteor would be of medium-slow speed.

The same study of video radiants by Molau has revealed a radiant in Eridanus active from September 3rd through the 23rd. Maximum activity occurred on September 6th. The Nu Eridanid (NUE) radiant is currently located at 04:44 (071) +03. This position is located on the Orion/Eridanus border, two degrees west of the fourth magnitude star known as Pi 5 Orionis. The radiant is best placed near 06:00 LDT when it lies highest in the sky. Hourly rates are expected to be near one, no matter your location. At 68 km/sec., these meteors are swift with the brightest members 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 twelve random meteors during the last hour before dawn from rural observing sites and three per hour during the evening hours. As seen from the mid-southern hemisphere (45S) morning rates would be near three 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. Morning 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 September 12/13, but may be used all week.