Meteor Activity Outlook for August 14-20, 2010
August 15, 2010
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.
Meteor activity kicks into high gear in August as seen from the northern hemisphere. The main reason for this activity surge is the Perseid shower that peaks on August 13. This shower is active most of the month and remains above the level of the sporadic background for a week centered on August 13. The sporadic activity is also increasing as seen from the northern hemisphere and is now nearly double the rates from just three months ago. As seen from south of the equator, meteor rates are still decent but falling rapidly. The sporadic rates seen at the beginning of the month will be twice as high as those seen during the last days of the month. The Perseid radiant does not rise high into the sky as seen in the southern hemisphere so rates from this shower are greatly reduced when compared to the northern hemisphere.
During this period the moon reaches its first quarter phase on Monday August 16th. At this time the moon will be located ninety degrees east of the sun and will set near 0100 local daylight time (LDT) for locations in the mid-northern latitudes of the northern hemisphere. This weekend the waxing crescent moon will set just prior to midnight for the locations mentioned above, and will be gone from the sky during the active morning hours. The estimated total hourly rates for evening observers this week is ~3 no matter your location. For morning observers the estimated total hourly rates should be ~35 from the northern hemisphere and ~20 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. During this period, moonlight reduces activity seen during the morning hours.
The radiant positions and rates listed below are exact for Saturday night/Sunday morning August 14/15. 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:
August Draconids (AUG)
Activity from the August Draconids (AUD) can be first detected near August 11th from a radiant located at 18:14 (273) +62. This position lies in southern Draco, ten degrees north of the second magnitude star Eltanin (Gamma Draconis). Maximum activity is not predicted until August 21st so current rates would be low, <1 per night. With an entry velocity of 23 km/sec. most of these meteors will appear to move slowly. The radiant is best placed near 2200 Local Daylight Time (10pm LDT) when it lies highest in the sky. Due to its high northern declination this shower is not well seen from the southern hemisphere.
Kappa Cygnids (KCG)
The Kappa Cygnids (KCG) are active from a wide radiant located at 19:06 (287) +52. This position is further south than previous publications. It has been updated through the use of video observations by the International Meteor Organization. The new location lies on the Cygnus/Draco border, three degrees southwest of the faint star Kappa Cygni. Maximum activity is now predicted to occur on August 14th. Current rates would be ~2 per hour from the northern hemisphere and <1 shower member per hour from south of the equator. With an entry velocity of 23 km/sec. most of these meteors will appear to travel slower than average. The radiant is best placed near 2300 LDT (11pm LDT) when it lies nearly overhead for much of the Northern Hemisphere. Due to its high northern declination this activity is not well seen from the southern hemisphere.
The wide Antihelion (ANT) radiant is now centered at 22:20 (335) -08. This area of the sky lies in central Aquarius, 3 degrees southeast of the 4th magnitude Theta Aquarii. 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 northern Piscis Austrinus, Capricornus, Aquarius, or southern Pegasus could be a candidate for this shower. Rates at this time should be ~2 per hour no matter your location. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of medium-slow speed.
Delta Aquariids (SDA)
The Delta Aquariids (SDA) reach maximum activity on Friday July 30th. The shower is still active from a radiant located at 23:36 (354) -12. This position lies in eastern Aquarius, 3 degrees northwest of the 4th magnitude star Omega2 Aquarii. The radiant is best placed near 0300 LDT, when it lies highest in the sky. The optimal latitudes for viewing this shower lie in the southern tropics where the radiant passes overhead. With an entry velocity of 42 km/sec., most activity from this radiant would be of average velocities. Expect rates of <1 per hour north of the equator and 1 per hour from the southern hemisphere.
August Piscids (AUP)
A new shower discovered by Sirko Molau and Juergen Rendtel from the IMO’s video database are the August Piscids (AUP). This shower is only active on eight nights from August 2-9 with maximum activity occurring on the 4th. At maximum, the radiant is located at 00:44 (011) +19. This area of the sky is located in northern Pisces, 10 degrees north of the 4th magnitude star Delta Piscium. This radiant is best placed during the last hour before dawn when it lies highest in a dark sky. Hourly rates are expected to be <1. With an entry velocity of 66 km/sec., the average August Piscid meteor would be swift.
A second new shower discovered by Sirko Molau and Juergen Rendtel from the IMO’s video database are the Eridanids (ERI). This shower is active from August 4th through the 18th with maximum activity occurring on the 9th. Hourly rates could reach ~2 per hour at maximum. The radiant is currently located at 03:12 (048) -09. This shower was observed by me during the Perseid maximum last week. The radiant is currently located at 03:12 (048) -09. This area of the sky is located in western Eridanus, 3 degrees east of the faint star Eta Eridani. This radiant is best placed during the last hour before dawn when it lies highest in a dark sky. Hourly rates are expected to be <1. With an entry velocity of 64 km/sec., the average Eridanid meteor would be swift.
The Perseids (PER) reached maximum activity on Friday August 13th with zenith hourly rates (ZHR’s) near 90. They are still active from a radiant located at 03:24 (051) +58. This position actually lies in southern Camelopardalis, eight degrees north of the second magnitude star Mirfak (Alpha Persei). The radiant is best placed during the last hour before the start of morning twilight when it lies highest in a dark sky. Current rates would be ~20 per hour, falling to <10 by the end of the week. Activity from the Perseids is not well seen south south of the equator and completely invisible south of 40 degrees south latitude. With an entry velocity of 61 km/sec., most activity from this radiant 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 AUG August Draconids 18h 14m +61 23 <1 <1 KCG Kappa Cygnids 19h 06m +52 23 1 <1 ANT Antihelions 22h 20m -08 30 2 3 SDA Delta Aquariids 23h 36m -12 42 1 2 ERI Eridanids 03h 12m -09 64 2 2 PER Perseids 03h 24m +58 61 3 2 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