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Meteor Activity Outlook for April 4-10, 2009

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  • Robert Lunsford
    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
    Message 1 of 1 , Apr 3 8:45 AM
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      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.

      Antihelion (ANT) - 13:52 (208) -11 Velocity - 30km/sec.
      Hourly Rates - Northern Hemisphere - 2 Southern Hemisphere - 2

      Zeta Cygnids (ZCY) - 20:00 (300) +39 Velocity - 41km/sec.
      Hourly Rates - Northern Hemisphere - <1 Southern Hemisphere - <1

      Clear Skies!
      Robert Lunsford
      International Meteor Organization
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