The Meteor Activity Outlook is a weekly summary of expected meteor activity written by Robert Lunsford, Operations Manager of the American Meteor Society and contributor to this blog. The original unedited version of this week’s Meteor Activity Outlook 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 first quarter phase on Saturday June 19th. At this time the moon will be located ninety degrees east of the sun and will set near 0100 for observers located in mid-northern latitudes. Next week the waxing gibbous moon will set later and later, shrinking the window of opportunity to view in optimum, dark conditions. The estimated total hourly rates for evening observers this week is ~2 for those in the northern hemisphere and ~3 for those south of the equator. For morning observers the estimated total hourly rates should be ~8 from the northern hemisphere and ~18 as seen from the 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.
The radiant positions and rates listed below are exact for Saturday night/Sunday morning June 19/20. 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:
June Bootids (JBO)
Perhaps a few June Bootids (JBO) may be seen this week during the evening hours, radiating from a position near 14h:44m (221) +49. This area of the sky lies in northern Bootes, ten degrees northwest of the fourth magnitude star Beta Bootis. This radiant is best placed as soon as it becomes dark. Rates at this time should be less than one for those located in the northern hemisphere and near zero for observers south of the equator. Maximum activity is expected on June 27th. With an entry velocity of 18 km/sec., the average June Bootid meteor would be of very slow speed.
The wide Antihelion (ANT) radiant is now centered at 18h:44m (281) -23. This area of the sky lies in western Sagittarius some four degrees northeast of the third magnitude star Kaus Borealis (Lambda Sagittarii). This radiant is best placed near 0200 local daylight time (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, southern Serpens Cauda, Sagittarius, Scutum, or southwestern Aquila could be a candidate for this shower. Rates at this time should be near one per hour as seen from the northern hemisphere and two 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.
Delta Piscids (DPI)
Recent studies of the IMO video database by Sirko Molau and Juergen Rendtel have revealed an active radiant in Pisces this time of year. The Delta Piscids (DPI) are only active for five nights (June 20-24) with maximum activity occurring on June 23rd. On that morning the radiant is located at 00h:44m (011) +06. This area of the sky is located in central Pisces near the fourth magnitude star Delta Piscium. This radiant is best placed during the last hour before dawn when it lies highest in a dark sky. Even at maximum activity hourly rates are expected to be less than one. This shower would be better seen from locations south of the equator where the nights are longer and the radiant would located higher in the eastern sky at the start of morning twilight. With an entry velocity of 71 km/sec., the average Delta Piscid meteor would be swift.
As seen from the mid-northern hemisphere (45N) one would expect to see approximately five 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 fourteen 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. Morning rates are slightly reduced due to moonlight.
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 JBO June Bootids 14h 44m +49 18 <1 0 ANT Antihelions 18h 44m -23 30 1 2 DPI Delta Piscids 00h 44m +06 71 <1 <1 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