Meteor Activity Outlook for October 17-23, 2009
October 16, 2009
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 in general increases in October when compared to September. A major shower (the Orionids) is active most of the month along with several 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 Sunday October 18th. At this time the moon lies near the sun and is invisible at night. Later in the period the waxing crescent moon will enter the evening sky but will not interfere with meteor observing. The estimated total hourly rates for evening observers this week is near five as seen from the northern hemisphere and two from the southern hemisphere. For morning observers the estimated total hourly rates should be near ~25 from the northern hemisphere and ~15 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 October 17/18. 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.
October Ursa Minorids (OUI)
A new radiant has been discovered in Ursa Minor which is active during this
period. The October Ursa Minorids (OUI) are active from October 16-28, with maximum occurring on the 24th. The current radiant position lies at 18:40
(280) +76. This position lies in northern Draco near the faint star 50 Draconis. The radiant is best placed just as soon as it becomes dark, when it lies highest in a dark sky. Meteors from the October Ursa Minorids strike the atmosphere at 28km/sec., which would produce meteors of slow velocity. Expected rates would be < 1 per hour, as seen from the northern hemisphere. Activity from this shower is not visible in the southern hemisphere due to the high northerly location of the radiant.
Northern Taurids (NTA)
A recent study of video radiants by Sirko Molau has revealed that activity from the Northern Taurids (NTA) does not begin until October 19th. This is nearly one month after pervious dates. Maximum activity does not occur until November 13th so current rates will be low, lower than its southern counterpart until late in the month. The radiant position lies at 02:32 (038) +19, which lies in central Aries, six degrees southeast of the second magnitude star Hamal (Alpha Arietis). The radiant is best placed near 0130 LDT, when it lies highest above the horizon. Meteors from the Northern Taurids strike the atmosphere at 29km/sec., which would produce meteors of slow velocity. Expected rates would be < 1 per hour, no matter your location.
Southern Taurids (STA)
The center of the large Southern Taurid (STA) radiant lies at 02:34 (038) +10. This position lies on the Aries/Cetus border, three degrees west of the fourth magnitude star Upsilon Ceti. Since the radiant is so large, any meteor from eastern Pisces, northern Cetus, or southern Aries could be a candidate for this shower. The radiant is best placed near the meridian at 0130 LDT, but activity may be seen all night long. Striking the atmosphere at 29 km/sec., the average Southern Taurid meteor travels slowly through the skies. Rates should be near ~3 per hour no matter your location.
Sigma Arietids (SSA)
A new radiant has been discovered in Aries which is active during this period. The Sigma Arietids (SSA) are active from October 12-19, with maximum occurring on the 19th. The current radiant position lies at 03:26 (051) +22,
which lies on the Aries/Taurus border, lying directly between the Pleiades star cluster and the fourth magnitude star Delta Arietis. The radiant is best placed near 0230 LDT, when it lies highest above the horizon. Meteors from the Sigma Arietids strike the atmosphere at 45km/sec., which would produce meteors of average velocity. Expected rates would be < 1 per hour, no matter your location.
The Orionids (ORI) are predicted to peak on Thursday morning October 22nd. This is a broad maximum so activity on the 21st and 23nd should also be good. The radiant is currently located at 06:12 (93) +15. This position lies in northwestern Orion one degree north of the fourth magnitude star Xi Orionis. The radiant rises near 2300 LDT and is best placed on the meridian near 0530 LDT. With maximum activity predicted for October 22, current rates for all locations would be near ~5 per hour as seen after midnight. At 66km/sec., the average Orionid is swift.
Epsilon Geminids (EGE)
The Epsilon Geminids (EGE) are active from October 16th through the 27th. Maximum activity occurs on the 19th. The radiant is currently located at 06:44 (101) +28. This position lies in northwestern Gemini, three degrees northwest of the third magnitude star Epsilon Geminorum. This position is also close to the Orionid radiant. Care must taken for correct shower association. The Orionids will be far more numerous. Current rates are most likely < 1 per hour. The radiant is best placed near 0600 LDT, when it lies highest above the horizon. At 70km/sec., the average Epsilon Geminid is swift.
October Ursa Majorids (OCU)
Activity from Ursa Major this time of year has been known for several years now. Recent studies by Sirko Molau has provided more precise data on this activity. The October Ursa Majorids (OCU) are active from October 12-19, with maximum occurring on the 15th. The current radiant position lies at 09:58 (149) +63, which lies in western Ursa Major, four degrees north of the third magnitude star Nu Ursae Majoris. The radiant is best placed during the last dark hour before the start of morning twilight, when it highest above the horizon in a dark sky. Meteors from the October Ursa Majorids strike the atmosphere at 53km/sec., which would produce meteors of medium-swift velocity. Expected rates would be < 1 per hour, no matter your location. This activity is not visible from the southern hemisphere due to the high northerly declination of the radiant.
Leonis Minorids (LMI)
The Leonis Minorids (LMI) are active from October 16-27 with maximum activity occurring on October 23rd. ZHR’s are usually low but the radiant is far removed from the Orionids and Epsilon Geminids so that any possible shower members should be easily identified. Hourly rates would be < 1 this week. This radiant is currently located at 10:21 (155) +37, which places it in northeastern Leo Minor, very close to 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 ~15 Sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near ~4 per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near ~4 per hour as seen from rural observing sites and ~1 per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Rates are reduced during the morning hours 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 except for showers of short duration, when the position on the night of maximum is listed.
Shower Name RA DEC Vel Rates km/s NH SH OUI Oct Ursa Minorids 18h40m +76 28 <1 <1 NTA Northern Taurids 02h32m +19 29 <1 <1 STA Southern Taurids 02h34m +10 29 3 3 SSA Sigma Arietids 03h26m +22 45 <1 <1 ORI Orionids 06h12m +15 67 5 5 OCU Oct. Ursa Majords 09h58m +63 53 <1 <1 LMI Leonis Minorids 10h21m +37 60 <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