Meteor Activity Outlook for April 4-10, 2009

Meteor activity picks up a bit during April as two major showers are active during the month. The first of these, the Lyrids, are active from the 16th through the 27th, with a pronounced maximum on the 22nd and 23rd. The Eta Aquariids start appearing near the 27th and reach maximum activity during the first week in May. Sporadic rates are low but steady as seen from the mid-northern hemisphere (45 N). Sporadic rates seen from the mid-southern hemisphere (45 S) rise this month toward a maximum in July.

During this period the moon reaches its full phase on Thursday April 9th. At this time the moon lies opposite the sun in the sky and remains above the horizon all night long. This weekend the waxing gibbous moon will set during the early morning hours allowing a small window of opportunity to observe meteor activity between moonset and the start of morning twilight. The estimated total hourly rates for evening observers this week is near two as seen from the northern hemisphere and three for those situated south of the equator. For morning observers the estimated total hourly rates should be near ten for those located in the mid-northern hemisphere (45 N) and fourteen for those viewing from the mid-southern hemisphere (45 S). Locations between these two extremes would see activity between the listed figures. These rates assume that you are watching from rural areas away from all sources of light pollution. 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 positions and rates listed below are exact for Saturday night/Sunday morning April 4/5. 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 wide Antihelion (ANT) radiant is now centered at 13:52 (208) -11. This area of the sky lies in southeastern Virgo, five degrees east of the first magnitude star Spica (Alpha Virginis). This radiant is best placed near 0200 LDT. Due to the large size of this radiant, any meteor radiating from eastern Virgo, western Libra, or northern Centaurus could be a candidate for this shower. Rates at this time should be near two per hour no matter your location. With an entry velocity of 30km/sec., the average Antihelion meteor would be of medium-slow speed.

The video studies of Sirko Molau have revealed a weak radiant active in Cygnus this time of year. The Zeta Cygnid (ZCY) radiant is currently located at 20:00 (300) +39. This area of the sky is located in western Cygnus, four degrees southwest of the second magnitude star Sadr (Gamma Cygni). Maximum activity occurs on April 10 so current rates are expected to remain less than one per hour. These meteors are best seen during the last dark hour before dawn, when the radiant lies highest above the horizon in a dark sky. This shower is best seen from the northern hemisphere, where the radiant lies high in the sky at dawn. At 41 km/sec. the Zeta Cygnids will usually produce meteors of medium velocity.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately eight 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 due to moonlight.

The table below presents a summary of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning but may be used all week.