During this period the moon reaches its full phase on Wednesday January 15th. At this time the moon will lie opposite the sun and will above the horizon all night long. This weekend the waning gibbous moon will set during the a few hours before dawn, allowing a couple of hours to view under dark conditions. The estimated total hourly meteor rates for evening observers this week is near 3 no matter your location. For morning observers the estimated total hourly rates should be near 10 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 this week due to moonlight. 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 January 11/12. 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 center of the large Antihelion (ANT) radiant is currently located at 08:16 (124) +18. This position lies in western Cancer, 5 degrees west of the 4th magnitude star Asellus Australis (Delta Cancri). Due to the large size of this radiant, Antihelion activity may also appear from western Leo, Gemini, Canis Minor, northwestern Hydra as well as Cancer. This radiant is best placed near 0100 LST, when it lies on the meridian and is located highest in the sky. Rates at this time should be near two per hour as seen from the northern hemisphere and one per hour from south of the equator. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of slow velocity.
There is a very remote chance that some meteor activity may occur this week due to the Earth’s close approach to the orbit of comet C/2012 S1 (ISON). It has been calculated that the particles from this comet are too far and too small to produce meteors in the Earth’s atmosphere. Yet we encourage observers to watch this week as nothing is certain. The most promising dates appear to be January 14-16. Unfortunately this coincides with the full moon and any activity will be difficult to observe due to the moon’s glare. The radiant would be located in central Leo just east of the 4th magnitude star Al Jabhah (Eta Leonis). This portion of the sky rises during the mid-evening hours and any activity would be best seen after midnight when Leo lies high in the sky. The expected entry velocity would be near 51 km/sec. which would produce meteors of medium-fast velocity.
The December Leonis Minorids (DLM) are active from a radiant located at 12:04 (181) +20. This position lies in western Coma Berenices, 6 degrees northeast of the 2nd magnitude star Denebola (Beta Leonis). These meteors are best seen near 0400 LST when the radiant lies highest above the horizon. This shower peaked on December 17th so current rates would be less than 1 per hour no matter your location. At 64 km/sec. the December Leonis Minorids produce mostly swift meteors.
The Canum Venaticids (CVN) are a new shower discovered by Peter Brown and his associates at the University of Western Ontario, using meteor orbits obtained by radar. This activity was verified by the IMO video network which has 271 possible candidates in its database. This shower is best seen from January 11-17, with maximum activity occurring on the 11th. Rates never exceed one shower member per hour yet it is the 3rd strongest radiant in the sky on the mornings of January 13 and 14. The radiant is located near 14:08 (212) +36, which places it in southeastern Canes Venatici. This position also lies 5 degrees southwest of the famous third magnitude double star known as Cor Caroli (Alpha Canum Venaticorum). Do not be too strict with this position as the radiant is not well defined at this point. Any meteors from this area this time of year should be suspected as possible Canum Venaticids. I would suggest using radiant distance and velocity to further determine possible shower association. These meteors encounter the atmosphere at 59 km/sec., which would produce mostly swift meteors. These meteors are best seen during the last few hours before dawn, when the radiant lies highest in a dark sky. This activity would be difficult to view from the southern hemisphere as the radiant lies low in the north at dawn.
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 2 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 9 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. Evening rates are lower during this period due to moonlight.
The table below presents a list of radiants that are expected to be active this week. Rates and positions are exact for Saturday night/Sunday morning except where noted in the shower descriptions.
|SHOWER||DATE OF MAXIMUM ACTIVITY||CELESTIAL POSITION||ENTRY VELOCITY||CULMINATION||HOURLY RATE||CLASS|
|RA (RA in Deg.) DEC||Km/Sec||Local Standard Time||North-South|
|Anthelions (ANT)||–||08:16 (124) +18||29||00:00||2 – 1||II|
|ISON||Jan 15||10:12 (153) +17||51||02:00||<1 – <1||IV|
|Dec. Leonis Minorids (DLM)||Dec 17||12:04 (181) +20||64||04:00||<1 – <1||II|
|Canum Venaticids (CVN)||Jan 11||14:08 (212) +36||59||06:00||<1 – <1||IV|