(meteorobs) Meteor Activity Outlook for January 15-21, 2011

[lunro.imo.usa at cox.net]

During this period the moon reaches its full phase on Wednesday January 19th. At that time the moon lies opposite of the sun and is present in the sky all night long. This weekend the waxing gibbous moon will set during the early morning hours, allowing a brief window of opportunity to view under conditions free of interfering moonlight during the last few hours before the start of morning twilight. 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. 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 15/16. 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 08:32 (128) +17. This area of the sky lies in central Cancer, three degrees west of the fourth magnitude star Delta Cancri. 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 eastern Gemini, Canis Minor, southern Lynx, northwestern Hydra, western Leo, 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. 

Studies by Sirko Molau and Juergen Rendtel of the IMO video database has revealed another radiant active in Cancer this time of year. The Southern Delta Cancrids (SCC) are only active from January 15th through the 18th. Maximum activity occurs on the 18th from a radiant located at 08:46 (132) +11. This position lies in southern Cancer, three degrees southwest of the fourth magnitude star Acubens (Alpha Cancri). This radiant is best placed near 0100 (LST) when it lies on the meridian and is located highest in the sky. At 29 km/sec. the Southern Delta Cancrids would produce meteors of medium-slow velocity. 

The December Leonis Minorids (DLM) are active from a radiant located at 12:15 (184) +19. This position lies in western Coma Berenices, five degrees northeast 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 one per hour as seen from the northern hemisphere and less than one per hour as seen from south of the equator. At 64km/sec. the December Leonis Minorids produce mostly swift meteors. 

An outburst of the Gamma Ursa Minorids (GUM) was recorded by Finnish video meteor observers on the night of January 20/21, 2010. Approximately ten bright members of this shower were recorded revealing a tight radiant near the position of 15:16 (229) +67. This position lies in southern Ursa Minor, five degrees south of the third magnitude star Gamma Urase Minoris. This radiant is best placed near 0500 (LST) when it lies highest above the horizon in a dark sky. At 30 km/sec. the Gamma Ursa Minorids would produce meteors of slow velocity. This shower is expected to be active from January 16-27. Very little activity is expected to be seen away from the night of maximum activity. No outburst is expected this year, especially with the full moon occurring two days before maximum activity. Observers with clear, transparent skies are urged to watch nonetheless. If the activity that occurred over Finland repeats itself this year, then I would expect it to occur over the western Atlantic region including the eastern coast of North America. 

Studies by Sirko Molau and Juergen Rendtel of the IMO video database has revealed a radiant active on the Corona Borealis/Hercules border this time of year. The Xi Corona Borealids (XCB) are only active from January 15th through the 20th. Maximum activity occurs on the 15th from a radiant located at 16:33 (248) +29. This position lies on the Corona Borealis/Hercules border, three degrees southwest of the third magnitude star Zeta Herculis. This radiant is best placed near 0500 (LST) when it lies highest above the horizon in a dark sky. At 50 km/sec. the Xi Corona Borealids would produce meteors of medium to swift velocity. 

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. 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. 

Antihelion (ANT) - 08:32 (128) +17   Velocity 30km/sec
Northern Hemisphere - 2 per hr Southern Hemisphere - 1 per hour

Southern Delta Cancrids (SCC) 08:46 (132) +11   Velocity 29km/sec
Northern Hemisphere - <1 per hr Southern Hemisphere - <1 per hour

December Leonis Minorids (DLM) 12:15 (184) +19   Velocity 64km/sec
Northern Hemisphere - 1 per hr Southern Hemisphere - <1 per hour

Gamma Ursa Minorids (GUM) 15:16 (229) +67   Velocity 30km/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/showers.html#X2010 

Clear Skies!
Robert Lunsford 
American Meteor Society