Meteor Activity Outlook for April 11-17, 2008

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 25th, with a pronounced maximum on the 22nd. Unfortunately this date coincides with a full moon this year so activity will be reduced. The Eta Aquarids start appearing near the 20th 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 first quarter phase on Saturday April 12th. At this time the moon will be located ninety degree east of the sun and will set near 0100 daylight time. With the moon situated well north of the celestial equator at this time, moonset will occur substantially later for observers at high northern latitudes and substantially earlier for high southern latitudes. Next week the waxing gibbous moon will set later in the morning limiting the time observers can view under dark skies. As seen from the mid-northern hemisphere (45 N) the estimated total hourly rates during the evening observers would be only one. For morning observers the estimated total hourly rates should be near nine. For those located in the mid-southern hemisphere (45 S) morning rates would be near fifteen and evening rates near two. 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 by moonlight.

The radiant positions and rates listed below are exact for Saturday night/Sunday morning April 12/13. 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 14:24 (216) -14. This area of the sky lies on the Virgo/Libra border near the faint star lambda Virginis. This radiant is best placed near 0200 LDT time when it lies on the meridian and is highest in the sky. Actually any meteor from southern Virgo or western Libra 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 30 km/sec., the average Antihelion meteor would be of medium-slow speed.

As seen from the mid-northern hemisphere (45N) the Sporadic rates are low, but fairly steady. One would expect to see approximately seven random meteors during the last hour before dawn from rural observing sites and only one per hour during the evening hours. As seen from the mid-southern hemisphere (45S) morning rates would be near thirteen per hour as seen from rural observing sites and two per hour during the evening hours. Evening rates are reduced due to moonlight.

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