Meteor Activity Outlook for December 25-31

During this period the moon reaches its last quarter phase on Tuesday December 28th. At this time the moon lies ninety degrees west of the sun and rises near midnight local standard time (LST) for those located in the mid-northern latitudes. With the moon waning and rising later each morning, this opens up another opportunity to view meteor activity under improving conditions. The estimated total hourly rates for evening observers this week is near four from the northern hemisphere and three for observers south of the equator. For morning observers the estimated total hourly rates should be near fifteen from the northern hemisphere and twelve as seen from the 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. Morning rates are reduced this week 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 25/26. 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:

Now that the activity from particles produced by comet 2P/Encke has ceased encountering the Earth, the Taurid showers for 2010 are over and we resume reporting activity from the Antihelion (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 Antihelion. 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 07:08 (107) +22. This position lies in central Gemini, two degrees west of the fourth magnitude star Delta Geminorum. Since the radiant is so large, Antihelion activity may also appear from eastern Taurus, northeastern Orion, western Cancer, 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 three per hour as seen from the northern hemisphere and two per hour from south of the equator. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of slow velocity.

Activity from the Alpha Hydrids (AHY) begin to appear on the morning of December 30th. This shower reaches maximum activity on the 31st from a radiant located at 08:24 (126) -08. This position lies in extreme western Hydra, fifteen degrees west of the second magnitude star Alphard (Alpha Hydrae). These meteors are best seen near 0200 LST when the radiant lies highest above the horizon. Hourly rates from this shower will be less than one per hour away from the night of maximum activity. Rates as high as two per hour may be seen on the morning of the 30th, no matter your location. At 45 km/sec. the Alpha Hydrids produce meteors of medium velocity.

The December Leonis Minorids (DLM) are active from a radiant located at 11:06 (167) +27. This position lies in a blank area of the sky where the borders of Leo Minor, Leo, and Ursa Major meet. The nearest bright stars are Nu and Xi Ursae Majoris which lie five degrees to the northeast. These meteors are best seen near 0500 LST when the radiant lies highest above the horizon. This shower peaked on December 20th 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.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately ten 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 eight 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 by moonlight during this period.The table below presents a condensed version of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning.