(meteorobs) Meteor Activity Outlook for September 15-21, 2012

[Robert Lunsford]

During this period the moon reaches its new phase on Saturday September 15th. At this time the moon is located near the sun and cannot be seen at night. As the week progresses the waxing crescent moon will enter the evening sky but will not interfere with meteor observing as it will set long before the active morning hours arrive. The estimated total hourly meteor rates for evening observers this week is near five 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 fifteen from the mid-northern hemisphere and eight 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.

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 15/16. 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 center of the large Southern Taurid (STA) radiant is currently located at 00:48 (012) +05. This position lies in southern Pisces, just south of the fourth magnitude star known as Delta Piscium. The radiant is so large that Southern Taurid activity may also appear from eastern Aquarius, north-central Cetus, southeastern Pegasus, southwestern Aries as well as Pisces. This radiant is best placed near 0200 local daylight time (LDT), when it lies on the meridian and is located highest in the sky. Since the maximum is still several weeks away (October 9), rates at this time are expected to be near one 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. Upon further research, the radiant is found to be active until September 28th, when activity stops abruptly. The radiant position is currently located at 03:38 (054) +40. This position lies in central Perseus, four degrees southeast of 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 would be near two per hour as seen from the northern hemisphere and less than one per hour as seen south of the equator. 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.

Surprisingly, one of the more active radiants in the September sky can be associated with the Orionids (ORI). These meteors have all of the characteristics of the October Orionids except for the strong rates. The radiant is currently located at 04:48 (072) +03, which is located in western Orion, four degrees south of Pi 3 Orionis, the brightest star in the "shield" of Orion. Rates would be near one per hour as seen during the last couple hours before dawn, when the radiant lies highest above the horizon in a dark sky. These meteors would be equally well seen either side of the equator. With an entry velocity of 67 km/sec., most activity from this radiant would be swift.

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 07:50 (117) +56. This position lies in northeastern Lynx, ten degrees southwest of the fourth magnitude star Omicron Ursae Majoris. 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 near one shower member 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 ten sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near four per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near five 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 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) - 00:48 (012) +05   Velocity 29km/sec
Northern Hemisphere - 1 per hr Southern Hemisphere - 1 per hour

September Epsilon Perseids (SPE) - 03:38 (054) +40   Velocity 66km/sec
Northern Hemisphere - 2 per hr Southern Hemisphere - <1 per hour

Orionids (ORI) 04:48 (072) +03   Velocity 67km/sec
Northern Hemisphere - 1 per hr Southern Hemisphere - 1 per hour

September Lyncids (SLY) 07:50 (117) +56   Velocity 41km/sec
Northern Hemisphere - 1 per hr Southern Hemisphere - <1 per hour

Clear Skies!
Robert Lunsford
American Meteor Society