(meteorobs) Meteor Activity Outlook for December 7-13, 2014

[Robert Lunsford]

During this period the moon reaches its first quarter phase on Monday December 9th. At this time the moon will lie 90 degrees east of the sun and will set near midnight local standard time (LST). This weekend the waxing crescent moon will set shortly before midnight and will not cause any interference to meteor observers out during the more active morning hours. As the week progresses though the moon sets later and later, causing considerable interference until it sets in the west.  This window of dark skies shrinks from 6 hours on Monday down to only 2 by the end of the week. The estimated total hourly meteor rates for evening observers this week is near 3 for observers located in the northern hemisphere and 2 for those viewing south of the equator. For morning observers the estimated total hourly rates should be near 28 for observers in the northern hemisphere and 24 for observers situated south of the equator. Evening rates are reduced during this period due to moonlight. 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.

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 7/8. 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 sources of meteoric activity are expected to be active this week:

The December Phoenicids (PHO) are a periodic shower that rarely produces noticeable activity. The only impressive display produced by this shower occurred in 1956 when ZHR's were near 100. Peak activity occurs on December 6. Little activity is expected away from the peak night. The radiant is currently located at 01:20 (020) -53. This position lies in southeastern Phoenix, 4 degrees northwest of the first magnitude star Archernar (Alpha Eridani). These meteors are best seen near 2000 (8pm) local standard time (LST), when the radiant lies highest above the horizon in a dark sky. Due to the southerly declination of the radiant, this shower is not visible north of the northern tropical areas. The deep southern hemisphere has the best chance of seeing any activity. At 22 km/sec. the Phoenicids produce very slow meteors.

Now that the activity from particles produced by comet 2P/Encke have ceased encountering the Earth, the Taurid showers for 2013 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 Anthelion. 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. There are several lists that have the Chi Orionids currently active, but we include them with the Anthelions as the celestial positions overlap. 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 05:52 (088) +23. This position lies on the borders of Taurus, Orion, and Gemini, 15 degrees north of the first magnitude orange star known as Betelgeuse (Alpha Orionis).  Anthelion activity may appear from eastern Taurus, northeastern Orion, southern Auriga as well as western Gemini. 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 1 per hour as seen from the northern hemisphere and less than 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 occurs on December 9th when the radiant is located at 06:40 (100) +08. This position lies in northern Monoceros directly between the bright stars Procyon (Alphs Canis Minoris) and Betelgeuse (Alpha Orionis) Current rates should be near 2 per hour no matter your location. 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) are in full swing during this period, peaking on Friday morning December 13. This weekend the radiant is located near 07:12 (108) +33. This position lies in northern Gemini, 4 degrees northwest of the 2nd magnitude star known as Castor (Alpha Geminorum). Rates this weekend should be near 5 per hour, increasing to near 50 per hour at maximum on Friday morning. Unfortunately as the week progresses the moon will begin to interfere with observations during the early morning hours. On the 13th, the 85% illuminated moon will not set until 2 hours before dawn. While this will cause major interference during the evening and early morning hours, there will be a short window of opportunity to view the display in dark skies after the moon has set. 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. At 35 km/sec. the Geminids produce mostly meteors of medium velocity.

The Puppid-Velids (PUP) are a vast complex of weak radiants located in the constellations of Puppis and Vela. Visual plots and photographic studies have revealed many radiants in this area during November and December. The combined strength of these radiants can produce a ZHR of 10. Actual hourly rates will be much less unless you happen to be observing from the deep Southern Hemisphere. The center of this activity is currently located at 08:16 (124) -45. This position lies in western Vela, 5 degrees northeast of the second magnitude star Suhail (Gamma Velorum). Peak rates occur near December 7. These meteors are best seen near 0300 LST when the radiant lies highest above the horizon in a dark sky. Observers located in the Southern Hemisphere have an advantage viewing this shower as the radiant will rise higher into their sky allowing more activity to be seen. Since the radiant lies low in the south for most northern hemisphere observers, meteors seen from north of the equator tend to be long in length and long-lasting. At 40 km/sec. the Puppid-Velids produce meteors of average velocity.

The Sigma Hydrids (HYD) are active from November 26 through December 21, with maximum activity occurring on December 6. The radiant is currently located at 08:24 (126) +02, which places it in western Hydra, just west of the small circular group of stars that form the head of Hydra. This position is also 10 degrees southeast of the brilliant zero magnitude star known as Procyon (Alpha Canis Minoris). These meteors are best seen near 0300 LST when the radiant lies highest above the horizon. Current rates should be near 5 per hour no matter your location. With an entry velocity of 62 km/sec., most activity from this radiant would be of swift speed.

The December Leonis Minorids (DLM) are active from a radiant located at 10:04 (151) +34. This position lies in western Leo Minor, near tje faint star known as 21 Leo Minoris. These meteors are best seen near 0400 LST when the radiant lies highest above the horizon. This shower peaks on December 17th so current rates would be near 1 per hour as seen from the northern hemisphere and less than 1 from south of the equator. At 64 km/sec. the December Leonis Minorids produce mostly swift meteors.

The December Alpha Draconids (DAD) are active from December 5-13. They are predicted to peak on December 8th from a radiant located at 13:01 (210) +60. This position actually lies in northeastern Ursa Major, 4 degrees northeast of the second magnitude star known as Alioth (Epsilon Ursae Majoris). 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. Current rates would most likely be near 1 per hour as seen from the northern hemisphere.  Observers south of the equator would see rates less than 1 per hour due to the lower radiant elevation.This is another shower discovered by Japanese observers using data from SonotaCo.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately 12 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 4 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 8 per hour as seen from rural observing sites and 3 per hour during the evening hours. Locations between these two extremes would see activity between the listed figures.

The list below presents a list of radiants that are expected to be active this 
week. Rates and positions are exact for Saturday night/Sunday morning unless 
stated in the activity descriptions.  
 
December Phoenicids (PHO) - 01:20 (020) -53   Velocity - 22km/sec. 
Northern Hemisphere - <1 per hr.   Southern Hemisphere - <1 per hr 
 
Anthelions (ANT) - 05:52 (088) +23  Velocity - 29km/sec. 
Northern Hemisphere - 1 per hr.   Southern Hemisphere - <1 per hr 
 
Monocerotids (MON) - 06:40 (100) +08   Velocity - 41km/sec. 
Northern Hemisphere - 2 per hr.   Southern Hemisphere - 2 per hr 
 
Geminids (GEM) - 07:12 (108) +33   Velocity - 41km/sec. 
Northern Hemisphere - 5 per hr.   Southern Hemisphere - 3 per hr 
 
Puppid-Velids (PUP) - 08:16 (124) -45   Velocity - 40km/sec. 
Northern Hemisphere - <1 per hr.   Southern Hemisphere - 5 per hr 
 
Sigma Hydrids (HYD) - 08:24 (126) +02   Velocity - 62km/sec. 
Northern Hemisphere - 5 per hr.   Southern Hemisphere - 5 per hr 
 
Dec. Leonis Minorids (DLM) - 10:04 (151) +34   Velocity - 64km/sec. 
Northern Hemisphere - 1 per hr.   Southern Hemisphere - <1 per hr 
 
Dec. Alpha Draconids (DAD) - 13:01 (210) +60	Velocity - 43km/sec. 
Northern Hemisphere - 1 per hr.   Southern Hemisphere - <1 per hr 
 
Clear Skies! 
Robert Lunsford 	 
American Meteor Society