Meteor Activity Outlook for October 13-19, 2006

Meteor rates continue to be strong as seen from the northern hemisphere. The antihelion radiant has now merged with the two Taurid radiants producing slow meteors during the late evening and early morning hours. Meteors from the Orionid radiant are visible most of the month. Strong sporadic rates continue during the morning hours as long as the moon is below the horizon. From the southern hemisphere, sporadic rates have reached their nadir and begin a slow recovery the second half of the month. Meteors from the Taurid and Orionid radiants also help to fill the southern skies with more activity than has been seen since July. A new moon during the peak of the Orionid shower is a plus for all and should help inflate meteor totals that have suffered since the Perseid maximum back in August.

This week the moon reaches its last quarter phase on Saturday October 14. At this time the moon will rise near 0100 local daylight time (LDT) and will interfere somewhat with meteor observing during the prime morning hours. The estimated total hourly rates for evening observers this week is near three for those north of the equator and one for observers south of the equator. For morning observers the estimated total hourly rates should be near twenty for northern observers and eight for those 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 due to moonlight.

The radiant positions listed below are exact for Saturday night/Sunday morning October 14/15. 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. 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.

These showers are expected to be active this week:

At this time of year debris from comet 2P/Encke produces a double radiant very close to the position of the antihelion radiant. From now through the end of November, it is impossible to resolve the antihelion meteors from those produced by comet 2P/Encke. Therefore we suggest that observers simply classify meteors from this area as either north or south Taurids. Although the radiants actually lie in Aries during October, they reach maximum activity in November when they are situated in the constellation of Taurus.

The Northern Taurid (NTA) radiant is now centered at 02:16 (034) +16. This position lies in central Aries, seven degrees southeast of the second magnitude star Hamal (Alpha Arietis). The Southern Taurid (STA) radiant lies at 02:24 (036) +11. This position lies in southern Aries, near the faint star Xi Arietis. The two radiants are separated by slightly over five degrees. Since they have nearly the same right ascension (celestial longitude), it is difficult to distinguish meteors that move north or south out of the radiants. It is slightly less difficult to distinguish those meteors traveling east or west.

These radiants are above the horizon most of the night and are best placed near 0100 LDT, when they lie on the meridian and are located highest in the sky. Rates at this time should be near two per hour for the southern radiant and one per hour for the northern radiant, regardless of your location. With an entry velocity near 30 km/sec., the average Taurid meteor would be of medium-slow speed.

The Orionids (ORI) are active from a radiant located at 06:04 (91) +15. This position lies in northeastern Orion, eight degrees northeast of the first magnitude star Betelgeuse (Alpha Orionis). The radiant rises near 2300 LDT and is best placed on the meridian near 0500. Current rates would be near five per hour over the weekend, increasing to near ten per hour late in the period. The Orionids reach a broad maximum centered on October 21, when hourly rates near twenty can be seen from rural locations, regardless of your location. At 64km/sec., the average Orionid is swift.

The Epsilon Geminids (EGE) peak on October 18 with a predicted ZHR of two. This radiant is currently located at 06:36 (99) +27, which places it in northwestern Gemini, two degrees northwest of the third magnitude star Epsilon Geminorum. The radiant is best placed near 0500 when it lies highest in the sky. To differentiate this shower from the nearby Orionids, one must have both radiants within their field of view. Meteors traveling north or south out of the radiants should be easy to classify. Those moving east or west will be more difficult as you must rely on path length and angular velocity to make a correct classification. At 70km/sec., the average Epsilon Geminid is swift with a high percentage of persistent trains.

Sporadic rates have reached the late year plateau for observers located in the northern hemisphere. One would expect to see perhaps twelve random meteors during the last hour before dawn from rural observing sites. During the first dark hour after the end of evening twilight, perhaps four random meteors can be seen per hour. Sporadic rates increase as the night progresses so rates seen near midnight would be near eight per hour. Sporadic rates seen from the southern hemisphere have reached their annual minimum. One would expect to see approximately three random meteors per hour during the last hour before dawn and one per hour during the first dark hour after the end of evening twilight. Rates near midnight would be near two per hour. Morning rates are reduced due to moonlight.

*For a detailed explanation on the different classes of meteor showers and other astronomical terms, please visit: http://www.amsmeteors.org/showers.html#X2006

Clear Skies!