(meteorobs) Meteor Activity Outlook for February 5-11, 2011

[lunro.imo.usa at cox.net]

During this period the moon reaches its first quarter phase on Thursday February 11th. At that time the moon lies ninety degrees east of the sun and is in the night sky from sunset to near midnight. This weekend the waxing crescent moon will set during the early evening hours and will not cause any problems with observing. The estimated total hourly rates for evening observers this week is near three as seen from the northern hemisphere and four as seen from the southern hemisphere. For morning observers the estimated total hourly rates should be near thirteen from the northern hemisphere and twenty as seen from south of the equator. 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 February 5/6. 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 showers are expected to be active this week: 

The wide Antihelion (ANT) radiant is now centered at 10:00 (150) +11. This area of the sky lies in southwestern Leo, very close to 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, Sextans, 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. 

The Alpha Centaurids (ACE) are active from a radiant located at 13:50 (208) -58. This position lies in southern Centaurus, only two degrees northwest of the brilliant first magnitude star Hadar (Beta Centauri). The radiant is best placed during the last dark hour before dawn, when it lies highest above the horizon. 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. At maximum activity on February 8th, rates rates from the southern hemisphere should be between 5-10 per hour. At 56km/sec. the Alpha Centaurids would produce mostly swift meteors. 

Studies by Sirko Molau and Juergen Rendtel of the IMO's video data base of nearly a half million meteors has revealed a weak radiant active in Hydra this time of year. The Pi Hydrids (PIH) is only active from February 4-8, when maximum activity occurring on the 8th. Activity this weekend would be produced from a radiant located at 14:12 (213) -23. This position lies in extreme eastern Hydra, four degrees north of the fourth magnitude star Pi Hydrae. Second magnitude Menkent (Theta Centauri) also lies a dozen degrees to the south. These meteors are best seen near 0500 LST when the radiant lies highest above the horizon. This shower is better seen from the southern hemisphere where the radiant lies much higher in the sky. At maximum I would expect rates to be less than one as seen from the northern hemisphere and one per hour as seen from south of the equator. At 70km/sec. the Pi Hydrids would produce mostly swift meteors. This shower may be part of the Centaurid complex that is active during February. 

Another radiant discovered by Sirko Molau and Juergen Rendtel, active this time of year, are the Beta Herculids (BHE). Like the Pi Hydrids, this is a shower of short duration with an activity period from February 10-14. Maximum activity occurs on February 13th. The radiant position for the morning of February 10th would be 16:13 (243) +26. This position lies in on the Corona Borealis/Hercules border, four degrees northwest of the third magnitude star Kornephoros (Beta Herculis). These meteors are best seen near 0500 LST when the radiant lies highest above the horizon in a dark sky. Rates on the morning of the 10th would most likely be less than one shower member per hour, no matter your location. At 56km/sec. the Beta Herculids would produce mostly swift meteors. 

As seen from the mid-northern hemisphere (45N) one would expect to see approximately eleven 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 be near fourteen per hour as seen from rural observing sites and three 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. 

Antihelion (ANT) - 10:00 (150) +11   Velocity 30km/sec
Northern Hemisphere - 2 per hr Southern Hemisphere - 2 per hour

Alpha Centaurids (ACE) 13:26 (202) -57   Velocity 56km/sec
Northern Hemisphere - <1 per hr Southern Hemisphere - 3 per hour

Pi Hydrids (PIH) 14:12 (213) -23   Velocity 70km/sec
Northern Hemisphere - <1 per hr Southern Hemisphere - 1 per hour

Beta Herculids (BHE) 16:13 (243) +26   Velocity 56km/sec
Northern Hemisphere - <1 per hr Southern Hemisphere - <1 per hour

For a detailed explanation on the different classes of meteor showers and other
astronomical terms, please visit:
http://www.amsmeteors.org/2010/12/2011-meteor-shower-list/

Clear Skies!
Robert Lunsford
American Meteor Society