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Meteor Activity Outlook for February 11-17, 2012

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  • Robert Lunsford
    During this period the moon reaches its last quarter phase on Tuesday February 14th. At that time the moon will be located ninety degrees west of the sun and
    Message 1 of 1 , Feb 9, 2012
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      During this period the moon reaches its last quarter phase on Tuesday February 14th. At that time the moon will be located ninety degrees west of the sun and will rise near 0100 local standard time (LST) for observers located in the mid-northern latitudes. This weekend the waning gibbous moon will severely hamper meteor observations as the moon will be above the horizon most of the night. Only a few hours after dusk will be free of interfering moonlight. Unfortunately meteor rates are lowest at this time but you might get lucky and see a fireball as now through April are good times to try and see early evening fireball activity. The estimated total hourly rates for evening observers this week is near two for observers in the northern hemisphere and five for those south of the equator. For morning observers the estimated total hourly rates should be near five as seen from mid-northern latitudes and eight from mid-southern latitudes. 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 this week due to 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 February 11/12. 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 large Antihelion (ANT) radiant is currently located at 10:24 (156) +08. This position lies in southwestern Leo, five degrees southwest of the bright first magnitude star Regulus (Alpha Leonis). Due to the large size of this radiant, Antihelion activity may also appear from Cancer, Sextans, Crater, and western Virgo as well as Leo. This radiant is best placed near 0100 LST, when it lies on the meridian and is located highest in the sky. Rates at this time should be near one per hour no matter your location. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of slow velocity.

      Studies of video radiants by Sirko Molau and Juergen Rendtel has revealed a radiant active in Hercules this time of year. The Beta Herculids (BHE) are only active for five nights and reach maximum activity on Monday February 13th. Hourly rates on that morning should be near one shower member per hour as seen from the northern hemisphere. Those situated south of the equator should average slightly less than one meteor per hour. The first signs of activity from this radiant appear on the morning of February 10th. The radiant position on the 13th lies at 16:24 (246) +24. This position lies in western Hercules, three degrees north of the third magnitude star Beta Herculis. The radiant is best placed during the last dark hour before dawn, when it lies highest above the horizon in a dark sky. At 56km/sec. the Beta Herculids would produce mostly swift meteors.

      The Alpha Centaurids (ACE) are active from a radiant located at 14:20 (215) -60. This position lies in southeastern Centaurus directly between the two brilliant stars 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 in a dark sky. 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 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 three 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 six per hour as seen from rural observing sites and four per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Morning rates are reduced this week due to moonlight.

      The table below presents a condensed version of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning.

      Antihelion (ANT) - 10:24 (156) +08 Velocity 30km/sec
      Northern Hemisphere - 1 per hr Southern Hemisphere - 1 per hour

      Alpha Centaurids (ACE) 14:20 (215) -60 Velocity 56km/sec
      Northern Hemisphere - <1 per hr Southern Hemisphere - 1 per hour

      Beta Herculids (BHE) 16:24 (246) +24 Velocity 56km/sec
      Northern Hemisphere - 1 per hr Southern Hemisphere - <1 per hour

      Clear Skies!
      Robert Lunsford
      International Meteor Organization
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