October 15, 2012 3 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 all month long 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 new phase on Monday October 15th. At this time the moon is located near the sun and is invisible at night. As the week progresses the waxing crescent moon will enter the evening sky but will not interfere with meteor observing. The estimated total hourly meteor rates for evening observers this week is near four for observers located at mid-northern latitudes and three for observers in mid-southern latitudes. For morning observers the estimated total hourly rates should be near twenty from the mid-northern hemisphere and thirteen from the mid-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 (the area of the sky where meteors appear to shoot from) positions and rates listed below are exact for Saturday night/Sunday morning October 13/14. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.
The following radiants are expected to be active this week:
The center of the large Southern Taurid (STA) radiant is currently located at 02:24 (036) +10. This position lies near on the Cetus/Aries border. The fourth magnitude star Xi 2 Ceti lies two degrees southeast from the center of the radiant. The radiant is so large that Southern Taurid activity may also appear from eastern Pisces, Aries, northern Cetus, northern Eridanus, and western Taurus. This radiant is best placed near 0200 local daylight time (LDT), when it lies on the meridian and is located highest in the sky. Maximum occurred on October 9th, but rates remain near maximum levels of three per hour for a week after this date. With an entry velocity of 29 km/sec., the average Southern Taurid meteor would be of slow velocity.
The Orionids (ORI) are producing 3-5 shower members per hour during the last few hours before dawn, when the radiant lies highest in the sky. The radiant is currently located at 06:00 (090) +16, which is in the northeastern Orion, eight degrees northwest of the brilliant first magnitude orange star Betelgeuse (Alpha Orionis). Orionid meteors are equally well seen either side of the equator. With an entry velocity of 67 km/sec., most activity from this radiant would be swift. Maximum activity is predicted to occur on the 22nd when hourly rates should be near twenty.
The Epsilon Geminids (EGE) are active all month long with low hourly rates. Even at maximum activity only three shower members per hour are expected. Recent research by the IMO has indicated an earlier maximum of October 15th, rather than October 19th. The radiant position is currently located at 06:27 (097) +29. This position actually lies within the borders of Auriga, just east of the faint star Kappa Aurigae. The radiant is also best placed during the last dark hour before dawn, when it lies highest above the horizon in a dark sky. Rates would be near two per hour as seen from the northern hemisphere and less than one per hour as seen south of the equator. With an entry velocity of 70 km/sec., most activity from this radiant would be swift.
Studies of the IMO’s video database by Sirko Molau and Juergen Rendtel has revealed a radiant active in Lynx this time of year. Earlier visual observations of this activity placed the radiant in eastern Auriga. Therefore the radiant is known as the Psi Aurigids (PSA). This radiant is active from October 8-18, with maximum activity occurring on the 12th. The radiant drift is not well established as positions jump around quite a bit during its ten day activity period. At maximum the radiant is located at 07:36 (113) +47. This position lies in a remote area of central Lynx. The nearest bright star is second magnitude Castor (Alpha Geminorum), which lies fifteen degrees to the south. This is a weak display and even at maximum activity rates would most likely be less than one shower member per hour, no matter you location. With an entry velocity of 68 km/sec., most activity from this radiant would be swift.
Studies of the IMO’s video database by Sirko Molau and Juergen Rendtel has also revealed a radiant active in Ursa Major this time of year. The October Ursae Majorids (OCU). are active from October 15-20, with maximum activity occurring on the 16th. At maximum the radiant is located at 09:36 (144) +65. This position lies in western Ursa Major, near the faint star 23 Ursae Majoris. This area of the sky is best placed during the last hour before morning twilight, when it lies highest above the horizon in a dark sky. At maximum activity rates would most likely be 1-2 per hour. Due to the high northern location of this radiant, these meteors are not well seen from the southern hemisphere. With an entry velocity of 54km/sec., most activity from this radiant would be medium-swift.
The Leonis Minorids (LMI) are active from October 16-27 with maximum activity occurring on October 23rd. Hourly rates would be less than one this week. This radiant is currently located at 10:16 (154) +38, which places it in northern Leo Minor, two degrees northwest of the fourth magnitude star Beta Leonis Minoris . The radiant is best placed just before dawn when it lies highest in a dark sky. This shower is better situated for observers situated in the northern hemisphere where the radiant rises far higher into the sky before the start of morning twilight. At 60km/sec., the average Leonis Minorid is swift.
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 three 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 two per hour during the evening hours. Locations between these two extremes would see activity between the listed figures.
The list 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.
Southern Taurids (STA) – 02:24 (036) +10 Velocity 29km/sec
Northern Hemisphere – 3 per hr Southern Hemisphere – 3 per hour
Orionids (ORI) 06:00 (090) +16 Velocity 67km/sec
Northern Hemisphere – 4 per hr Southern Hemisphere – 4 per hour
Epsilon Geminids (EGE) 06:27 (097) +29 Velocity 70km/sec
Northern Hemisphere – 2 per hr Southern Hemisphere – <1 per hour
Psi Aurigids (PSA) 07:36 (114) +47 Velocity 68km/sec
Northern Hemisphere – <1 per hr Southern Hemisphere – <1 per hour
October Ursae Majorids (OCU) – 09:36 (144) +65 Velocity 54km/sec
Northern Hemisphere – 1 per hr Southern Hemisphere – <1 per hour
Leonis Minorids (LMI) – 10:16 (154) +38 Velocity 60km/sec
Northern Hemisphere – <1 per hr Southern Hemisphere – <1 per hour
American Meteor Society