Meteor Activity Outlook for December 8-14, 2012

During this period the moon reaches its new phase on Thursday December 13th. At this time the moon is located near the sun and will be invisible at night. This weekend the waning crescent moon will rise during the early morning hours. It will be a minor inconvenience that can be overcome by simply viewing with the moon at your back. The estimated total hourly meteor rates for evening observers this week is near four for observers located at mid-northern latitudes and three for observers in mid-southern latitudes. For morning observers the estimated total hourly rates should be near twenty from the mid-northern hemisphere and sixteen from the mid-southern hemisphere. 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. Rates are slightly reduced during the morning hours during this period 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 December 8/9. 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:

Meteors from comet 46PWirtanen? There is the possibility that we may be able to see meteor activity from comet 46PWirtanen as the Earth passes through several filaments of material produced when the comet passed through perihelion during the first half of the 20th century. This is strictly an evening display as any meteors from this source would have a radiant of 23:48 (357) +04. This position lies in western Pisces, just east of the circle of faint stars known as the “Circlet”. This area of the sky is best seen as it becomes dark as it culminates between 1800 and 1900 (6pm and 7pm) local standard time. The first of these encounters is with the material shed in 1947. The expected peak is at 06:21 Universal Time (UT) on December 11th. This corresponds to 22:21 (10:21pm) PST and 23:21 (11:21pm) MST on Monday evening December 10th. The radiant is too low for any activity to be seen in the eastern half of North America. The second encounter is material from 1941. This peak is expected to occur at 10:20 UT on December 12th. This is too late for North America but observers in Hawaii may be able to see some of this activity. The third encounter is produced from the 1934 return. This peak is expected to occur at 12:30 UT on December 13th. This timing favors the western Pacific area. The last possible encounter is produced by the 1927 return. This peak is expected to occur at 00:02 UT on December 14th. This corresponds to 19:02 (7:02pm) EST and 18:02 (6:02pm) CST on the evening of December 13th. This timing favors the eastern half of North America. If any meteors are produced from this source, they would be extremely slow.

The last of the Northern Taurids (NTA) can be seen this weekend from a radiant centered at 05:26 (082) +27. This area of the sky lies in northeastern Taurus, two degrees south of the second magnitude star El Nath (Beta Tauri). The radiant is best placed near 0100 LST, when it lies highest above the horizon. Maximum activity occurred on November 13th so current hourly rates would be near one from the northern hemisphere and less than one from south of the equator. Meteors from the Northern Taurids strike the atmosphere at 29km/sec., which would produce meteors of slow velocity.

The Monocerotids (MON) are active from December 7th through the 18th. Peak activity occurs on December 8th with the radiant is located at 06:36 (099) +08. This position lies in northern Monoceros, eight degrees east of the first magnitude orange star Betelgeuse (Alpha Orionis). Current rates should be near one 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) reach maximum activity on Thursday evening/Friday morning December 13/14, when approximately 75 shower members can be seen each hour from rural observing sites. While the Geminids are currently the most active radiant in the sky, rates this weekend will only be near five shower members per hour. Rates will increase dramatically as we approach the maximum date and the moon wanes. The radiant is currently located at 07:14 (109) +33. This position lies in northern Gemini, four degrees west of the second magnitude star Castor (Alpha Geminorum). Although Geminid meteors can be seen all night long, they are best seen near 0200 LST when the radiant lies highest above the horizon. 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. This is one of the few displays that can be well seen prior to midnight. Geminid meteors seen just after dusk will be very long with a long duration. This is due to the fact that the radiant will lie near the horizon and any Geminid meteor seen be just be skimming the upper regions of the atmosphere. Therefore they will take longer to disintegrate in the much less dense portion of the atmosphere. Geminid meteors strike the atmosphere at 35km/sec, which will produce meteors of medium-slow 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 zenith hourly rate (ZHR) of ten at maximum, which occurs near December 7. 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 08:08 (124) -45. This position lies in western Vela, three degrees northeast of the second magnitude star Gamma Velorum. 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. At 40 km/sec. the Puppid-Velids produce meteors of average velocity.

The Sigma Hydrids (HYD) are active from November 26 through December 20. Maximum activity occurred on December 6 and this radiant is currently the third most active in the sky. The radiant is located at 08:24 (126) +02. This position lies in western Hydra, just west of the group of fourth magnitude stars that make up the “head” of the water serpent. These meteors are best seen near 0300 LST when the radiant lies highest above the horizon. Current rates would be near three per hour no matter your location. At 61 km/sec. the Sigma Hydrids produce mostly swift meteors.

The December Leonis Minorids (DLM) are active from a radiant located at 10:08 (152) +36. This position lies in central Leo Minor, approximately twelve degrees north 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 17th 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 64 km/sec. the December Leonis Minorids produce mostly swift meteors.

Lastly, the December Alpha Draconids (DAD) are active from December 4-16. Maximum activity occurred on December 5. The radiant is currently located at 13:40 (205) +60. This position actually lies in northeastern Ursa Major, direct between the fourth magnitude star Thuban (Alpha Draconis) and the second magnitude double star Mizar (Zeta 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. Expected hourly rates would be less than one no matter your location. At 44 km/sec. the Alpha Draconids produce mostly medium speed meteors.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately seven sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near three per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near four 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. Morning rates are reduced 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 .