Meteor Activity Outlook for October 1-7, 2011
October 1, 2011 2 Comments
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.
Meteor activity in general increases in October when compared to September. A major shower (the Orionids) is active most of the month along with many minor showers. Both branches of the Taurids become more active as the month progresses, providing slow, graceful meteors to the nighttime scene. The Orionids are the big story of the month reaching maximum activity on the 22nd. This display can be seen equally well from both hemispheres which definitely helps out observers located in the sporadic-poor southern hemisphere this time of year.
During this period the moon reaches its first quarter phase on Tuesday October 4th. At this time the half illuminated moon will lie ninety degrees east of the sun and will set near midnight local daylight time (LDT). This weekend the waxing crescent moon will set during the early evening hours and will not interfere with meteor observing. The estimated total hourly rates for evening observers this week is near four as seen from the northern hemisphere and three as seen from the southern hemisphere. For morning observers the estimated total hourly rates should be near twelve as seen from mid-northern latitudes and seven from mid-southern latitudes. 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 October 1/2. 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:
The Draconids (GIA) (also known as the Giacobinids) reach maximum activity on October 8. This year a possible outburst is predicted to be visible from Asia, Africa, and Europe. Lesser activity may be seen on the 6th and 7th and the 9th and 10th. The nearly full moon this time of month will severely hamper observations. Detailed articles are available on the websites of the International Meteor Organization (http://www.imo.net/draconids2011) and the American Meteor Society (http://www.amsmeteors.org/2011/09/possible-draconid-outburst-in-2011/). The radiant is located at 17:28 (262) +54, which places it in southern Draco, two degrees northwest of the third magnitude star Rastaban (Beta Draconis). This star is one of the four that form the prominent head of Draco, also known as the “Lozenge”. Due to the extreme northern declination, this shower is only visible from the southern tropics northward. The radiant is best placed just as it becomes dark during the evening hours. At 20km/sec., the average Draconid is extremely slow.
The Southern Taurid (STA) radiant is now centered at 01:40 (025) +07. This area of the sky lies in southeastern Pisces, two degrees southwest of the fourth magnitude star Omicron Piscium. This radiant is best placed near 0200 local daylight time (LDT), when it lies on the meridian and is located highest in the sky. Rates at this time should be near two per hour no matter your location. With an entry velocity of 27 km/sec., the average Southern Taurid meteor would be of medium-slow speed. While looking at this area of the sky, notice how bright the variable star Mira (Omicron Ceti) is these nights. It normally is too dim to be seen with the naked eye but now stands at second magnitude, nearly the brightest star in the constellation of Cetus the whale. It lies approximately ten degrees southeast from the center of the STA radiant or just six degrees southeast of the fourth magnitude star Al Rischa (Alpha Piscium). It is probably near peak magnitude and will soon begin fading.
A new shower of bright meteors radiating from near the Draco/Camelopardalis border was discovered in 2005 and has repeated itself in most years since. The October Camelopardalids (OCT) are active on only two nights but shower members are bright and should be easy to observe. The 2011 display is predicted to occur on October 5th and 6th. The estimated position of the radiant on the 5th is 10:48 (162) +79. The nearest easy star to identify the radiant is 4th magnitude SAO1551. This area of the sky is circumpolar from nearly the entire northern hemisphere. The radiant lies highest above the horizon in a dark sky at both dusk and at dawn. Due to this unusual situation this shower would be totally invisible from the southern hemisphere. With an entry velocity of 45km/sec., most members of the October Camelopardalids would be of medium-swift velocity.
As seen from the mid-northern hemisphere (45N) one would expect to see approximately ten 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 five per hour as seen from rural observing sites and one 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 GIA Draconids 17h 28m +54 20 <1 <1 STA Southern Taurids 01h 40m +07 27 2 2 OCT Oct. Camelopardalids 10h 48m +79 45 <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