Meteor Activity Outlook for December 8-14, 2006

December is the last month of strong activity as seen in the northern hemisphere. During the first half of the month minor showers are active in the constellations of Taurus (Antihelions), Monoceros (Monocerotids), Puppis (Puppid-Velids), Hydra (Sigma Hydrids), and Leo (Coma Berenicids). Strong sporadic rates continue during the morning hours as long as the moon is below the horizon. Rates increase significantly with the arrival of the Geminids during the second week of the month. From the southern hemisphere, sporadic rates are increasing in strength toward a peak in January. Meteors from the above minor showers are also well seen from south of the equator. The Geminids also increase the southern activity, but not nearly to the extent that is witnessed in the northern hemisphere.

This week the moon reaches its last quarter phase on Tuesday December 12. At this time the moon will rise near midnight local standard time and will be present in the sky the remainder of the morning. This weekend the glare from the waning gibbous moon will cause problems for meteor observers. Only the brighter meteors will be visible. This situation will improve with each passing night as the moon's phase wanes and it rises later each night. The estimated total hourly rates for evening observers this week is near four for those north of the equator and three for observers south of the equator. For morning observers the estimated total hourly rates should be near thirty for northern observers and sixteen 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 this week.

The radiant positions listed below are exact for Saturday night/Sunday morning December 9/10. 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. This method 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.

These showers are expected to be active this week:

The Antihelion (ANT) radiant is now centered at 06:00 (090) +23. This area of the sky lies in western Gemini near the fourth magnitude star 1 Geminorum. This radiant is best placed near 0100 LST when it lies on the meridian and is highest in the sky. Rates at this time should be near two per hour as seen from the northern hemisphere and one per hour for observers located south of the equator. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of medium-slow speed. Don't confuse these meteors with the much stronger Geminid radiant, which lies a bit further east.

The Monocerotids (MON) are currently active from a radiant located at 06:40 (100) +08. This area of the sky is located in northern Monoceros, eight degrees south of the 2nd magnitude star Alhena (Gamma Geminorum). These meteors are best seen near 0100 local standard time when the radiant lies highest above the horizon. The peak for the Monocerotids occurred on December 8 with an expected ZHR of three. This shower would be equally well seen from both hemispheres. At 42 km/sec. the Monocerotids produce meteors of average velocity.

The Geminids (GEM) peak on the night of December 13/14. Rates will rise steadily this week as we approach the maximum and the moon wanes. The current radiant is located at 07:12 (108) +33. This area of the sky is located in northern Gemini, five degrees west of the second magnitude star Castor (Alpha Geminorum). These meteors are best seen near 0200 local standard time when the radiant lies highest above the horizon. This shower is best suited for the Northern Hemisphere but some activity can be seen south of the equator when the radiant culminates low in the northern sky. At 35 km/sec. the Geminids produce meteors of average velocity. A detailed article on how to observe and photograph the Geminids is available at: http://www.amsmeteors.org/showers.html#geminids

The Puppid-Velids (PUP) is a vast complex of weak radiants located in the constellations of Puppis and Vela. Visual plots and photographic studies have revealed many radiants in this area during November and December. The combined strength of these radiants can produce a ZHR of ten. Actual hourly rates will be much less unless you happen to be observing from the deep Southern Hemisphere. The center of this activity is currently located at 08:20 (125) -45. This position lies in western Vela, three degrees northeast of the second magnitude star Gamma Velorum. These meteors are best seen near 0300 LST when the radiant lies highest above the horizon in a dark sky. Observers located in the Southern Hemisphere have an advantage viewing this shower as the radiant will rise higher into their sky allowing more activity to be seen. At 40 km/sec. the Puppid-Velids produce meteors of average velocity.

The Sigma Hydrids (HYD) are currently active from a radiant located at 08:24 (126) +02. This area of the sky is located in western Hydra, three degrees southwest of the fourth magnitude star Sigma Hydrae. These meteors are best seen near 0300 local standard time when the radiant lies highest above the horizon. The predicted peak for the Sigma Hydrids occurs on December 12 when the ZHR reaches two. Recent studies have indicated that this shower may peak earlier in the month so careful monitoring this week of any activity would be valuable. Current rates would be near one shower member per hour. At 58 km/sec. the Sigma Hydrids produce meteors of average to swift velocity.

The Coma Berenicids (COM) are usually noticed a bit later in the month. Video studies by Sirko Molau have shown that the shower actually begins near December 5 and peaks near December 20. During the early portion of its activity it provides approximately five percent of the overall meteor activity. The current location of this radiant would near 10:04 (151) +35. This area of the sky is located in central Leo Minor. This radiant is probably responsible for the many reports of activity in Leo during the month of December. These meteors are best seen near 0500 local standard time when the radiant lies highest above the horizon. At 65 km/sec. the Coma Berenicids will usually produce meteors of swift velocity.

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 passed their annual minimum and are rising again. One would expect to see approximately five random meteors per hour during the last hour before dawn and two per hour during the first dark hour after the end of evening twilight. Rates near midnight would be near three per hour. Morning rates are reduced due to moonlight this week.

Clear Skies!