(meteorobs) Meteor Activity Outlook for January 28-February 3, 2012

[Robert Lunsford]

February offers the meteor observer in the northern hemisphere a couple of weak showers plus falling sporadic rates. This may not seem too exiting but you never know when surprises are in store. An errant earthgrazer from the Centaurid complex may shoot northward. Better yet, a bright fireball may light up the sky. February is the start of the fireball season, when an abundance of fireballs seem to occur. This lasts well into April and seems to occur mostly during the early evening hours.

Observers in the southern hemisphere are treated to the Alpha Centaurid peak on the 8th plus the entire Centaurid complex of radiants is active all month long. Sporadic rates also peak this month south of the equator this month adding to the celestial show.

During this period the moon reaches its first quarter phase on Tuesday January 31st. At this time the moon will be located ninety degrees east of the sun and will set near 0100 local standard time (LST) for observers located in the mid-northern latitudes. This weekend moonlight will be restricted to the evening hours, allowing the more active morning hours to be free from interfering moonlight.  The estimated total hourly rates for evening observers this week is near two for observers in the northern hemisphere and three for those south of the equator. For morning observers the estimated total hourly rates should be near nine as seen from mid-northern latitudes and fifteen from mid-southern latitudes. 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.

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 28/29. 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:

The large Antihelion (ANT) radiant is currently located at 09:28 (142) +13. This position lies in western Leo, ten degrees northwest of the bright first magnitude star Regulus (Alpha Leonis). Due to the large size of this radiant, Antihelion activity may also appear from Cancer, Sextans, and northwestern Hydra as well as Leo. 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 no matter your location. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of slow velocity.

The last of the December Leonis Minorids (DLM) are seen this week from a radiant located at 13:04 (196) +16. This position lies in southern Coma Berenices, two degrees southwest of the fourth magnitude star Diadem (Alpha Comae Berenices). These meteors are best seen near 0500 local standard time (LST) when the radiant lies highest above the horizon. This shower peaked on December 20th so current rates would be less than one per hour no matter your location. At 64 km/sec. the December Leonis Minorids produce mostly swift meteors.

The Alpha Centaurids (ACE) are now active from a radiant located at 13:20 (200) -57. This position lies in southeastern Centaurus, five degrees southwest of the second magnitude star Epsilon Centauri. The radiant is best placed during the last dark hour before dawn, when it lies highest above the horizon in a dark sky. At this position, these meteors are only visible south of 35 degrees north latitude. The further one is located south (down to 60S) the better the radiant is situated in the sky. Current rates from the southern hemisphere is near one per hour. At 56km/sec. the Alpha Centaurids would produce mostly swift 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 one per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near twelve 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. Evening rates are reduced this week due to moonlight.

The list below presents a condensed version of the expected activity this week.
Rates and positions are exact for Saturday night/Sunday morning.

Antihelion (ANT) - 09:28 (142) +13   Velocity 30km/sec
Northern Hemisphere - 2 per hr Southern Hemisphere - 2 per hour

December Leonis Minorids (DLM) 13:04 (196) +16   Velocity 64km/sec
Northern Hemisphere - <1 per hr Southern Hemisphere - <1 per hour

Alpha Centaurids (ACE)  13:20 (200) -57   Velocity 56km/sec
Northern Hemisphere - <1 per hr Southern Hemisphere - 1 per hour

Clear Skies!
Robert Lunsford
American Meteor Society