(meteorobs) Meteor Activity Outlook for December 13-19, 2014

[Robert Lunsford]

During this period the moon reaches its full phase on Sunday December 14th. At this time the moon rises near midnight local standard time (LST) and will remain in the sky the remainder of the night. Viewing conditions improve with each passing night as the moon wanes and rises later each morning. The estimated total hourly meteor rates for evening observers this week is near 4 as seen from the northern hemisphere (45N) and 3 as seen from southern tropical latitudes (25S). For morning observers the estimated total hourly rates should be near 65 as seen from the northern hemisphere and 30 as seen from below 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. Note that the hourly rates listed below are estimates as viewed from dark sky sites away from urban light sources. Observers viewing from urban areas will see less activity as only the brightest meteors will be visible from such locations. Morning rates are reduced during this period due to the bright moon.

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 December 13/14. 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.

These sources of meteoric activity are expected to be active this week.

Now that the activity from particles produced by comet 2P/Encke has ceased encountering the Earth, the Taurid showers for 2014 are over and we resume reporting activity from the Anthelion (ANT) radiant. This is not a true radiant but rather activity caused by the Earth's motion through space. As the Earth revolves around the sun it encounters particles orbiting in a prograde motion that are approaching their perihelion point. They all appear to be radiating from an area near the opposition point of the sun, hence the name Anti-helion. These were once recorded as separate showers throughout the year but it is now suggested to bin them into their category separate from true showers and sporadics. This radiant is a very large oval some thirty degrees wide by fifteen degrees high. Activity from this radiant can appear from more than one constellation. The position listed here is for the center of the radiant which is currently located at 06:20 (095) +23. This position lies in western Gemini, 5 degrees west of the third magnitude star known as Mebsuta (Epsilon Geminorum). Anthelion activity may also appear from eastern Taurus, northeastern Orion, or southern Auriga. This radiant is best placed near midnight LST when it lies on the meridian and is highest in the sky. Rates at this time should be near 2 per hour as seen from the northern hemisphere and 1 per hour from south of the equator. With an entry velocity of 30 km/sec., the average Anthelion meteor would be of slow velocity.

The Monocerotids (MON) are active from November 27th through December 17th. Peak activity occurred on December 9th so current rates should be near 1 per hour no matter your location. The radiant is located at 07:00 (105) +07. This position lies in eastern Monoceros, 10 degrees west of the zero magnitude star Procyon (Alpha Canis Minoris).  The Monocerotids are best seen near 0100 LST when the radiant lies highest above the horizon. At 41 km/sec. the Monocerotids produce mostly meteors of medium velocity.

The Geminids (GEM) will peak on Saturday evening/Sunday morning December 13/14 from a radiant located at 07:37 (113.3) +32. This position is located very close to the bright 2nd magnitude star known as Castor (Alpha Geminorum). Expected maximum rates depend on your location and sky transparency. The half-illuminated moon will also compromise rates seen after midnight. Midnight rates should be near 20 per hour for urban observers. Those viewing from suburbs should see 30 Geminids per hour near midnight. Rural observers should be treated to at least 50 Geminids per hour. These rates should hold from midnight through 2am before falling as the radiant sets and the moonlight intensifies.    Geminid activity can be seen from the southern hemisphere but at much reduced rate. As seen from south of the equator, Geminid activity could only be seen for a few hours before and after 0200 LST. Rates will fall drastically with each passing night no more will be seen after the 17th. At 34 km/sec. the Geminids produce mostly meteors of medium velocity.

The Sigma Hydrids (HYD) are active from November 24 through December 21, with maximum activity occurring on December 6. The radiant is currently located at 08:40 (130) +01 , which places it in western Hydra, 2 degrees south of the 4th magnitude star known as Sigma Hydrae. These meteors are best seen near 0400 LST when the radiant lies highest above the horizon. Current rates should be near 2 per hour no matter your location. With an entry velocity of 61 km/sec., most activity from this radiant would be of swift speed.

The Eta Hydrids (EHY) were recently discovered by members of of the Croatian Meteor Network. This radiant is active from December 10-18 with maximum activity occurring on December 12. The radiant is currently located at 09:00 (135) +02 , which places it in western Hydra, 2 degrees west of the 4th magnitude star known as Theta Hydrae. This position is close to the Sigma Hydrids so care must be taken to separate the two sources. These meteors are best seen near 0400 LST when the radiant lies highest above the horizon. Current rates should be less than 1 per hour no matter your location. With an entry velocity of 63 km/sec., most activity from this radiant would be of swift speed.

The December Leonis Minorids (DLM) are active from December 6th through January 18th. The radiant is currently located at 10:25 (156) +33. This position lies in central Leo Minor, approximately 10 degrees northeast of the third magnitude star Zeta Leonis. These meteors are best seen near 0500 LST when the radiant lies highest above the horizon. This shower peaks on December 21st so current rates would be near 2 per hour as seen from the northern hemisphere and 1 per hour as seen from south of the equator. At 63 km/sec. the December Leonis Minorids produce mostly swift meteors.

The last of the Psi Ursa Majorids (PSU) will be seen this week from a radiant located at 12:00 (180) +39. This position lies in a remote area of southeastern Ursa Major, 15 degrees south of the 2nd magnitude star known as Phecda (Gamma Ursae Majoris). This area of the sky is best placed during the last hour before dawn, when it lies highest above the horizon in a dark sky. Current rates would most likely be less than one per hour no matter your location. At 61km/sec., the average Psi Ursa Majorid meteor would be swift.

The December Chi Virginids (XVI) were discovered by members of SonotaCo based on video observations obtained in 2007 and 2008. This radiant is active from December 8-24 with maximum activity occurring on the 17th. The radiant is currently located at 12:43 (191) -10. This area of the sky is located in southern Virgo, 10 degrees west of the bright, 1st magnitude star known as Spica (Alpha Virginis). Rates would most likely be less than 1 per hour no matter your location. At 69km/sec., the average December Chi Virginid meteor would be swift.

The December Sigma Virginids (DSV) were discovered by John Greaves using data from SonotoCo.  This radiant is active from December 6-31 with maximum occurring on the 24th. The current radiant location is 13:04 (196) +06, which places it in central Virgo, 5 degrees south of the third magnitude star Vindemiatrix (Epsilon Virginis). These meteors are best seen during the last dark hour before dawn, when the radiant lies highest above the horizon in a dark sky. At 68 km/sec. the December Sigma Virginids would produce mostly swift meteors.

Activity from the Ursids (URS) should begin to appear during the late-week period from a radiant located at 13:58 (210) +76. This position lies in eastern Ursa Minor, fifteen degrees east of the second magnitude star Kochab (Beta Ursa Minoris). It must be remembered that the length of degrees are smaller in high declinations so the radiant is actually closer to this star than these figures imply. These meteors are best seen during the last dark hour before dawn, when the radiant lies highest above the horizon in a dark sky. This shower is not well seen from the southern hemisphere. Maximum activity is not expected until Monday December 22th, so current hourly rates this week would probably be less than one. On the morning of maximum, hourly rates of between 5-10 Ursids may be seen. At 30 km/sec. the Ursids produce mostly medium-slow meteors.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately 8 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 3 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 5 per hour as seen from rural observing sites and 2 per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Morning rates are reduced during this period due to moonlight.

Anthelion (ANT) - 06:20 (095) +23  Velocity - 30km/sec. 
Northern Hemisphere - 2 per hr.   Southern Hemisphere - 1 per hr. 
 
Monocerotids (MON) - 07:00 (105) +07  Velocity - 41km/sec. 
Northern Hemisphere - 1 per hr.   Southern Hemisphere - 1 per hr. 
 
Geminids (GEM) - 07:37 (113) +32  Velocity - 34km/sec. 
Northern Hemisphere - 50 per hr.   Southern Hemisphere - 20 per hr. 
 
Sigma Hydrids (HYD) -08:40 (130) +01	  Velocity - 61km/sec. 
Northern Hemisphere - 2 per hr.   Southern Hemisphere - 2 per hr. 
  
Eta Hydrids (EHY) - 09:00 (135) +02  Velocity - 63km/sec. 
Northern Hemisphere - <1 per hr.   Southern Hemisphere - <1 per hr 
 
Dec. Leonis Minorids (DLM) - 10:25 (156) +33  Velocity - 63km/sec. 
Northern Hemisphere - 2 per hr.   Southern Hemisphere - 1 per hr. 
 
Psi Ursa Majorids (PSU) - 12:00 (180) +39  Velocity - 61km/sec. 
Northern Hemisphere - <1 per hr.   Southern Hemisphere - <1 per hr. 
 
Dec. Chi Virginids (XVI) - 12:43 (191) -10  Velocity - 69km/sec. 
Northern Hemisphere - <1 per hr.   Southern Hemisphere - <1 per hr 
 
Dec. Sigma Virginids (DSV) - 13:04 (196) +06 Velocity - 68km/sec. 
Northern Hemisphere - <1 per hr.   Southern Hemisphere - <1 per hr 

Ursids (URS) - 13:58 (210) +76  Velocity - 30km/sec. 
Northern Hemisphere - <1 per hr.   Southern Hemisphere - <1 per hr 
  
Clear Skies! 
Robert Lunsford 	 
American Meteor Society