Meteor Activity Outlook for 9-15 December 2023

Gary Mead captured this multi-bursting fireball on July 20, 2023, at 22:37 MDT (4:37 UT on July 21) from the Tony Grove Campground, Utah, USA. ©Gary Mead

During this period, the moon reaches its new phase on Wednesday December 13th. On that night the moon will be near the sun and will be invisible at night. This weekend the waning crescent moon will rise during the early morning hours, still bright enough to be a nuisance.  This can be overcome by simply keeping the moon out of your field of view. The estimated total hourly rates for evening observers this weekend should be near 4 as seen from mid-northern latitudes (45N) and 3 as seen from tropical southern locations (25S) For morning observers, the estimated total hourly rates should be near 40 as seen from mid-northern latitudes (45N) and 20 as seen from tropical southern locations (25S). The actual rates seen 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 brighter 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 9/10. 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. I have also included charts of the sky that display the radiant positions for evening, midnight, and morning. The center of each chart is the sky directly overhead at the appropriate hour. These charts are oriented for facing south but can be used for any direction by rotating the charts to the desired direction. 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. Radiants that rise after midnight will not reach their highest point in the sky until daylight. For these radiants, it is best to view them during the last few hours before dawn. It must be remembered that meteor activity is rarely seen at its radiant position. Rather they shoot outwards from the radiant, so it is best to center your field of view so that the radiant lies toward 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 sporadic. Meteor activity is not seen from radiants that are located far 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

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On the evening of December 12^th, the Earth is predicted to encounter debris from comet 46P/Wirtanen. The timing of this encounter is at 10:14 universal time which favors New Zealand, Australia, and southeast Asia including the Philippines and the many island nations north of Australia. These meteors will have a predicted radiant of 00:29 (007) -39, which places it in southern Sculptor some 4 degrees north of the 2^nd magnitude star known as Ankaa (alpha Phoenicis). This area of the sky lies low in the south at dusk for observers in the northern hemisphere but lies much higher in the sky as seen from the southern hemisphere. These meteors could be faint and difficult to observe. The velocity of these meteors would be very slow at only 10km/sec so they should be easily noticed should activity occur. Should your skies be clear near this date and time everyone is encouraged to check for any activity from this source.

Now that the activity from particles produced by comet 2P/Encke have ceased encountering the Earth, the Taurid showers for 2022 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 pro-grade 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 a 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 06:00 (090) +23. This position lies in western Gemini, 1 degree west of the 4th magnitude star known as 1 Geminorum. This radiant is best placed near 01:00 local standard time (LST) when it lies on the meridian and is highest in the southern sky. Rates at this time should be near 3 per hour as seen from the northern hemisphere and 2 per hour as seen 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 a radiant located at 06:41 (100) +08. This area of the sky is located in northwestern Monoceros, 5 degrees south of the 3rd magnitude star known as Alzirr (xi Geminorum). This position is 7 degrees away from the NOO radiant so care must be taken to differentiate between these two showers. This radiant best placed near 0200 LST, when it lies highest in the southern sky. Rates should be near 2 per hour no matter your location. With an entry velocity of 41 km/sec., most activity from this radiant would be of medium speed. This shower is active from November 23^rd through December 24^th, with maximum activity occurring on December 11^th.

The Geminids (GEM) are active from November 19^th through December 24^th, peaking on December 14^th. The Geminid radiant is currently located at 07:18 (109) +33. This area of the sky lies in northeastern Gemini, 4 degrees northwest of the 2nd magnitude star known as Castor (alpha Geminorum). These meteors are best seen near 02:00 LST, when the radiant lies nearly overhead. Rates are expected to be near 20 per hour this weekend, increasing to 75 per hour by Thursday. Note that these rates are only seen from the northern hemisphere near 02:00, when the radiant lies highest in the sky. Rates from the southern hemisphere should be near 5 per hour this weekend and near 25 at maximum. With an entry velocity of 33km/sec, most of these meteors would appear to possess a medium velocity.

The sigma Hydrids (HYD) are active from a radiant located at 08:27 (127) +02. This area of the sky is located in western Hydra, 3 degrees southwest of the 4^th magnitude star known as Minchir (sigma hydrae). These meteors are active from November 24 through January 7^th, with the main maximum activity occurring on December 7^th. The activity profile is not smooth as there are several minor peaks of activity throughout the activity period. The last peak occurs on Monday morning December 11th. To best see these meteors, face toward the south during the last couple of hours prior to dawn. With an entry velocity of 59km/sec, most of these meteors would appear swift. Expect to see 2 per hour no matter your location.

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. Activity from this source begins around December 1st. The center of this activity is currently located at 08:10 (122) -45. This position lies in western Vela, 2 degrees northeast of the 2nd magnitude star known as gamma Velorum. Peak rates occur near December 7. These meteors are best seen near 0300 LST when the radiant lies highest above the southern 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. Note: these are also listed as the “e Velids” from several sources.

The Comae Berenicids (COM) are a long duration shower active from December 5th through February 4th. Maximum activity occurs on December 16th. The radiant is currently located at 10:08 (152) +35, which places it in Leo Minor, near the spot occupied by the 4^th magnitude star known as 21 Leonis Minoris. These meteors would be best seen near 05:00 LST, when the radiant lies highest in the eastern sky. Current rates would be near 2 per hour as seen from the northern hemisphere and near one as seen from south of the equator. At 63km/sec., these meteors would produce mostly swift meteors.

Sporadic meteors are those meteors that cannot be associated with any known meteor shower. All meteor showers are evolving and disperse over time to the point where they are no longer recognizable. Away from the peaks of the major annual showers, these sporadic meteors make up the bulk of the activity seen each night. As seen from the mid-Northern Hemisphere (45N) one would expect to see during this period approximately 10 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 7 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 these listed figures. Morning rates are slightly reduced due to moonlight.

The list below offers the information in tabular form. Rates and positions are exact for Saturday night/Sunday morning.

Class Explanation: A scale to group meteor showers by their intensity:

• Class I: the strongest annual showers with Zenith Hourly Rates normally ten or better.
• Class II: reliable minor showers with ZHR’s normally two to ten.
• Class III: showers that do not provide annual activity. These showers are rarely active yet have the potential to produce a major display on occasion.
• Class IV: weak minor showers with ZHR’s rarely exceeding two. The study of these showers is best left to experienced observers who use plotting and angular velocity estimates to determine shower association. These weak showers are also good targets for video and photographic work. Observers with less experience are urged to limit their shower associations to showers with a rating of I to III.