Meteor activity picks up a bit during April as the Lyrids become active during the month. They are active from the 18th through the 25th, with a pronounced maximum on the 22nd. Sporadic rates during April are steady as seen from both hemispheres with southern observers enjoying twice the activity that can be seen from the mid-northern hemisphere.
During this period the moon reaches its last quarter phase on Wednesday April 3rd. At this time the moon is located ninety degrees west of the sun and will rise near 0200 local daylight time as seen from mid-northern latitudes. This weekend the waning gibbous moon will rise during the late evening hours, allowing a short period of dark skies between dusk and moon rises. The remainder of the night will be compromised by bright moonlight. The estimated total hourly meteor rates for evening observers this week is near two as seen from the northern hemisphere and three as seen from south of the equator. For morning observers the estimated total hourly rates should be near five from the mid-northern hemisphere and seven from the mid-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. Rates are reduced during the morning hours due to interfering 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 March 30/31. 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 Anthelion (ANT) radiant is currently located at 13:32 (203) -09. This position lies in southern Virgo, only two degrees northeast of the first magnitude star Spica (Alpha Virginis). These meteors may be seen all night long but the radiant is best placed near 0200 LDT when it lies on the meridian and is 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 Anthelion meteor would be of slow velocity.
Studies of the IMO video database by Sirko Molau and Juergen Rendtel has revealed a weak radiant active in the constellation of Cygnus this time of year. The Nu Cygnids (NCY) are active from April 2 through May 4 with maximum activity occurring on April 18. The current radiant position (April 2) lies at 19:52 (298) +35. This position lies in central Cygnus, close to the fourth magnitude star known as Eta Cygni. No matter your location, rates at this time are expected to be less than one per hour. At 42km/sec. the Nu Cygnids would produce meteors of average velocity.
The Zeta Cygnids (ZCY) are active from March 22 through April 10, with maximum activity occurring on the morning of April 6th. This stream was first noticed by Z. Sekanina in a study of radio meteor streams. It has been recently verified in the IMO video database producing low activity during late March and early April. The radiant is currently located near 19:56 (299) +40. This position lies in western Cygnus, five degrees west of second magnitude Sadr, (Gamma Cygni). This position is close to that of the Nu Cygnid radiant so care must be taken once that shower becomes active on April 2nd. With the moon situation this week, the best mornings to try to view this activity would be from April 3rd through the following weekend. The radiant is best placed in a dark sky just before dawn. At 45km/sec. this shower would produce meteors of medium velocityFinding Nemo-Combo Banner.
As seen from the mid-northern hemisphere (45N) one would expect to see approximately three 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 six per hour as seen from rural observing sites and three per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Rates are reduced during the morning hours during this period 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 .
|SHOWER||DATE OF MAXIMUM ACTIVITY||CELESTIAL POSITION||ENTRY VELOCITY||CULMINATION||HOURLY RATE||CLASS|
|RA (RA in Deg.) DEC||Km/Sec||Local Daylight Time||North-South|
|Anthelions (ANT)||–||13:04 (196) -07||30||02:00||2 – 2||II|
|Nu Cygnids (NCY)||Apr 18||19:52 (298) +35||42||08:00||<1 – <1||IV|
|Zeta Cygnids (ZCY)||Apr 06||19:56 (299) +40||45||08:00||<1 – <1||IV|