January 31, 2011
February offers the meteor observer in the northern hemisphere a couple of weak showers plus falling sporadic rates. This may not seem too exiting but you never know when surprises are in store. An errant earthgrazer from the Centaurid complex may shoot northward. Better yet, a bright fireball may light up the sky. February is the start of the fireball season, when an abundance of fireballs seem to occur. This lasts well into April and seems to occur mostly during the early evening hours.
Observers in the southern hemisphere are treated to the Alpha Centaurid peak on the 8th plus the entire Centaurid complex of radiants is active all month long. Sporadic rates are slightly less than those seen in January, but still stronger than those witnessed north of the equator.
During this period the moon reaches its new phase on Thursday February 3rd. At that time the moon lies near the sun and is invisible at night. This weekend the waning crescent moon will rise during the early morning hours but will not cause any problems as long as you keep it out of your field of view. The estimated total hourly rates for evening observers this week is near three no matter your location. For morning observers the estimated total hourly rates should be near thirteen no matter your location. 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 January 29/30. 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 09:32 (143) +13. This area of the sky lies in western Leo, eight degrees northwest of the first magnitude star Regulus (Alpha Leonis). This radiant is best placed near 0100 local standard time (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 northwestern Hydra, western Leo, or Cancer could be a candidate for this shower. Rates at this time should be near two per hour no matter your location. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of medium-slow speed.
December Leonis Minorids (DLM)
This is the last week to see activity from the December Leonis Minorids (DLM) until next December. Activity would be produced from a radiant located at 13:07 (197) +13. This position lies in northern Virgo, two degrees northeast of the second magnitude star Vindemiatrix (Epsilon Virginis). 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 less than one per hour no matter your location. At 64km/sec. the December Leonis Minorids produce mostly swift meteors.
Alpha Centaurids (ACE)
The Alpha Centaurids (ACE) are now active from a radiant located at 13:26 (202) -57. This position lies in southeastern Centaurus, three degrees southwest of the second magnitude star Epsilon Centauri. The radiant is best placed during the last dark hour before dawn, when it lies highest above the horizon in a dark sky. At this position, these meteors are only visible south of 35 degrees north latitude. The further one is located south (down to 60S) the better the radiant is situated in the sky. Current rates rates from the southern hemisphere is near one per hour. At 56km/sec. the Alpha Centaurids would produce mostly swift meteors.
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 two per hour. As seen from the mid-southern hemisphere (45S), morning rates would also be near twelve 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 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 09h 32m +13 30 2 2 DLM Dec Leonis Minorids 13h 07m +13 64 <1 <1 ACE Alpha Centaurids 13h 26m -57 56 <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