(meteorobs) Meteor Activity Outlook for September 8-14, 2012

[Robert Lunsford]

During this period the moon reaches its last quarter phase on Saturday September 8th. At this time the moon is located ninety degrees west of the sun and will rise near midnight local daylight time (LDT) for observers located in the mid-northern latitudes. As the week progresses the moon's phase will wane and it will rise later in the morning, creating more favorable viewing conditions for meteor observers. The estimated total hourly meteor rates for evening observers this week is near four for observers located at mid-northern latitudes and three for observers in mid-southern latitudes. For morning observers the estimated total hourly rates should be near thirteen from the mid-northern hemisphere and four from the mid-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 during this period due to moonlight.

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 September 8/9. 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 radiants are expected to be active this week:

The Southern Taurid (STA) radiant becomes active this week and will replace the Antihelion radiant until December. These two radiants are superimposed upon each other in the sky and impossible to separate. The center of the large  STA radiant is currently located at 00:24 (006) +01. This position lies in blank area of southern Pisces, midday between the bright stars Deneb Kaitos (Beta Ceti) and Algenib (Gamma Pegasi). These two stars also roughly mark the southern and northern boundaries of the STA radiant. Southern Taurid activity may also appear from eastern Aquarius as well as Pisces, Cetus, and Pegasus. This radiant is best placed near 0200 LDT, when it lies on the meridian and is located highest in the sky. Rates at this time are expected to be near two per hour no matter your location. With an entry velocity of 29 km/sec., the average Southern Taurid meteor would be of slow velocity.

The September Epsilon Perseids (SPE) is the strongest shower of the month. They are active from September 4th through the 12th with maximum activity occurring on the 9th. The radiant position is currently located at 03:08 (047) +41. This position lies in western Perseus, very close to the famous eclipsing variable star known as Algol (Beta Persei). The radiant is also best placed near 0500 LDT, when it lies highest above the horizon. Rates at maximum are near five shower members per hour. 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.

Studies of the IMO's video database by Sirko Molau and Juergen Rendtel has revealed a new radiant active in Lynx this time of year. The September Lyncids (SLY) are active from September 6th through the October 5th with maximum activity occurring on September 27th. The radiant position is currently located at 07:04 (106) +56. This position lies in northwestern Lynx, a dozen degrees northeast of the second magnitude star Menkalinan (Beta Aurigae) . The radiant is best placed during the last dark hour before dawn, when it lies highest above the horizon in a dark sky. Rates are variable for this radiant throughout the activity period. Current rates are expected to be 1-2 shower members per hour as seen from mid-northern latitudes. This radiant is not well placed to be viewed from the southern hemisphere. With an entry velocity of 64 km/sec., most activity from this radiant would be swift.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately seven 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 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 due to to moonlight during this period.

The list 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.

Southern Taurids (STA) - 00:24 (006) +01   Velocity 29km/sec
Northern Hemisphere - 2 per hr   Southern Hemisphere - 2 per hour

September Epsilon Perseids (SPE) - 03:08 (047) +41   Velocity 66km/sec
Northern Hemisphere - 3 per hr Southern Hemisphere - <1 per hour

September Lyncids (SLY)  07:04 (106) +56   Velocity 41km/sec
Northern Hemisphere - 1 per hr Southern Hemisphere - <1 per hour

Clear Skies!
Robert Lunsford
American Meteor Society