(meteorobs) Meteor Activity Outlook for February 12-18, 2011

[lunro.imo.usa at cox.net]

During this period the moon reaches its full phase on Friday February 18th. At that time the moon lies opposite the sun in the sky and is in the sky all night long. This weekend the waxing gibbous moon will set during the early morning hours, allowing a few hours of dark sky before the onset of morning twilight. This window of opportunity shrinks with each passing night until it is essentially zero on Thursday February 17th. The estimated total hourly rates for evening observers this week is near two as seen from the northern hemisphere and three 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 12/13. 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 10:28 (157) +08. This area of the sky lies in southern Leo, two degrees west of the fourth magnitude star Rho 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, western Virgo, or eastern 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 14:24 (216) -61. This position lies in southeastern Centaurus, directly between the brilliant first magnitude star Hadar (Beta Centauri) and Rigel Kentaurus (Alpha 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 30 degrees north latitude. The further one is located south (down to 60S) the better the radiant is situated in the sky. Current rates from the southern hemisphere should be between 3-5 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 Hercules this time of year. The Beta Herculids (BHE) 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 13th would be 16:24 (246) +24. This position lies in western Hercules, three degrees north 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 are most likely 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 one 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 two per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Evening rates are reduced 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.

Antihelion (ANT) - 10:28 (157) +08   Velocity 30km/sec
Northern Hemisphere - 2 per hr Southern Hemisphere - 2 per hour

Alpha Centaurids (ACE) 14:24 (216) -61 Velocity 56km/sec
Northern Hemisphere - <1 pe  r hr Southern Hemisphere - 4 per hour

Beta Herculids (BHE) 16:24 (246) +24   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