May 28, 2011
The following is a slightly edited version of Bob Lunsford’s excellent weekly summary of meteor activity. The original version can be found at the American Meteor Society’s site.
June is another slow month for meteor activity. There are no major showers active in June and only the Antihelion source can be counted on for continuous activity. Even the Antihelion is located so far south this time of year that rates rarely exceed two per hour as seen from the northern hemisphere. Sporadic rates reach their nadir in June as seen from the mid-northern hemisphere (45 N). Sporadic rates seen from the mid-southern hemisphere (45 S) continue to rise this month toward a maximum in July.
During this period the moon reaches its new phase on Wednesday June 1st. At this time the moon will lie near the sun and will not be visible at night. This weekend the waning crescent moon will not cause any problems viewing meteor activity as it is very thin and rises late in the morning. The estimated total hourly rates for evening observers this week is near three as seen from the northern hemisphere and four as seen from the southern hemisphere. For morning observers the estimated total hourly rates should be near eight from the northern hemisphere and eighteen as seen from south of the equator. 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 May 28/29. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.
The following showers are expected to be active this week:
According to Peter Jenniskens, the Earth will pass only 0.0011 AU (100,000 miles) from the 1952 trail of comet 73P/Schwassmann-Wachmann 3 near 05:45 UT on June 2. This corresponds to 1:45am EDT, 12:45am CDT, 11:45pm MDT (on June 1st), and 10:45pm PDT (on June 1st). Unfortunately the comet was relatively inactive on this return and this trail is not expected to produce any activity this year. Still, I would urge observers to try and verify any activity near
the times listed above. This variable shower is known as the Tau Herculids (TAH) and last produced activity back in 1995, when parent comet broke up into several pieces. The radiant is expected to be near the position of 15:44 (236) +41. This area of the sky is located where the boundaries of Bootes, Corona Borealis, and Hercules meet. The nearest easily seen star is Mu Bootis, which lies four degrees southwest of the radiant in northern Bootes. This area of the sky lies high in the east once it becomes dark. It passes nearly overhead near 0100 local daylight time. Luckily, the moon is near new and will not interfere with observing at all. Please post your results either positive or negative to meteorobs as soon as possible. If no activity occurs as expected, then the next close approach will occur in 2017 from the 1941 trail. Looking even further ahead, in 2022, the Earth encounters many trails of SW3, including two of the very active 1995 trails, and an outburst of activity is expected.
The wide Antihelion (ANT) radiant is now centered at 17:24 (261) -23. This area of the sky lies in southeastern Ophiuchus, two degrees northeast of the third magnitude star Theta Ophiuchi. This radiant is best placed near 0200 LDT when it lies on the meridian and is located highest in the sky. Due to the large size of this radiant, any meteor radiating from southern Ophiuchus, western Sagittarius, Serpens Cauda, or Scorpius could be a candidate for this shower. Rates at this time should be near two per hour as seen from the northern hemisphere and three per hour as seen from south of the equator. 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) 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 fifteen 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.
The list below presents a condensed version of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning.
Shower Name RA DEC Vel Rates km/s NH SH TAU Tau Herculids 15h 44m +41 15 <1 <1 ANT Antihelions 17h 24m -23 30 2 3 RA - Right Ascension DEC - Declination Vel - Velocity relative to Earth (in km per sec) Rates - Rate of visible meteors per hour from a dark site NH - Northern Hemisphere SH - Southern Hemisphere