The Meteor Activity Outlook is a weekly summary of expected meteor activity written by Robert Lunsford, Operations Manager of the American Meteor Society and contributor to this blog. The original unedited version of this week’s Meteor Activity Outlook can be found at the American Meteor Society’s site.
January sees a peak of sporadic activity for the southern hemisphere while rates seen north of the equator begin a steady downward turn that continues throughout the first half of the year. The sporadic activity is good for both hemispheres, but not as good as it was for northern observers in December. Once the Quadrantids have passed the shower activity for January is very quiet.
During this period the moon reaches its first quarter phase on Wednesday January 12th. At this time the moon lies ninety degrees east of the sun and sets near midnight LST (Local Standard Time). This weekend the waxing crescent moon will set during the mid-evening hours allowing a majority of the night to be free from interfering moonlight. The estimated total hourly rates for evening observers this week is near three from the northern hemisphere and three for observers south of the equator. For morning observers the estimated total hourly rates should be near eighteen from the northern hemisphere and sixteen 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. Evening rates are reduced by 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 January 8/9. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.
The following showers are expected to be active this week:
The wide Antihelion (ANT) radiant is now centered at 08:04 (121) +19. This area of the sky lies in western Cancer, ten degrees southeast of the bright first magnitude star Pollux (Beta Geminorum). This radiant is best placed near 0100 (LST) when it lies on the meridian and is located highest in the sky. Due to the large size of this radiant, any meteor radiating from eastern Gemini, Canis Minor, southern Lynx, northwestern Hydra, or Cancer could be a candidate for this shower. 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.
December Leonis Minorids (DLM)
The December Leonis Minorids (DLM) are active from a radiant located at 11:55 (179) +22. This position lies in a blank area near the Leo/Coma Berenices border, seven degrees north of the second magnitude star Denebola (Beta Leonis). These meteors are best seen near 0500 LST when the radiant lies highest above the horizon. This shower peaked on December 20th so current rates would be near two per hour as seen from the northern hemisphere and one per hour as seen from south of the equator. At 64km/sec. the December Leonis Minorids produce mostly swift meteors.
The Quadrantids (QUA) or January Bootids are active from January 1st through the 10th. A sharp maximum occurred between 2300 on January 3 and 0400 Universal Time on the 4th when zenith hourly rates exceeded 100 per hour. The last remnants of this shower for 2011 may be seen this weekend from a radiant located at 15:32 (233) +49. This position lies in a bare region of extreme northern Bootes, ten degrees south of the fourth magnitude star Iota Draconis. At 42 km/sec. the Quadrantids produce meteors of medium velocity.
As seen from the mid-northern hemisphere (45N) one would expect to see approximately fourteen Sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near two per hour. As seen from the mid-southern hemisphere (45S), morning rates would also be near fourteen 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. Rates are reduced during the evening hours due to moonlight.
The list below presents a condensed version of the expected activity this week.
Rates and positions are exact for Saturday night/Sunday morning.
Shower Name RA DEC Vel Rates km/s NH SH ANT Antihelions 08h 04m +19 30 2 1 DLM Dec Leonis Minorids 11h 55m +22 64 2 1 QUA Quadrantids 15h 32m +49 42 <1 <1 RA - Right Ascension DEC - Declination Vel - Velocity relative to Earth (in km per sec) Rates - Rate of visible meteors per hour from a dark site NH - Northern Hemisphere SH - Southern Hemisphere