(meteorobs) Meteor Activity Outlook for February 18-24, 2012

[Robert Lunsford]

During this period the moon reaches its new phase on Tuesday February 21st. At that time the moon will be located near the sun and will not be visible at night. This will be the best time this month to view meteor activity. This weekend the waning crescent moon will rise during the late morning hours and will not interfere with meteor observations. The estimated total hourly rates for evening observers this week is near three for observers in the northern hemisphere and five for those south of the equator. For morning observers the estimated total hourly rates should be near seven as seen from mid-northern latitudes and fourteen 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.

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 February 18/19. 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 11:00 (165) +05. This position in southwestern Leo is very easy to find as the brilliant planet Mars currently lies only seven degrees to the northeast. Due to the large size of this radiant, Antihelion activity may also appear from Crater, Sextans, southwestern Coma Berenicids, and western Virgo as well as Leo. This radiant is best placed near 0100 local standard time (LST), when it lies on the meridian and is located highest in the sky. Rates at this time should be near one 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 Alpha Centaurids (ACE) may be seen this weekend from a radiant located at 14:53 (223) -62. This position lies in southeastern Centaurus, two degrees southeast of the brilliant zero magnitude star Rigel Kentaurus (Alpha 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 25 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 would be less than 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 six sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near two per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near fourteen per hour as seen from rural observing sites and four per hour during the evening hours. Locations between these two extremes would see activity between the listed figures.

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

Antihelion (ANT) - 11:00 (165) +05   Velocity 30km/sec
Northern Hemisphere - 1 per hr Southern Hemisphere - 1 per hour

Alpha Centaurids (ACE) 14:53 (223) -62   Velocity 56km/sec
Northern Hemisphere - <1 per hr Southern Hemisphere - <1 per hour

Clear Skies!
Robert Lunsford
American Meteor Society