Meteor Activity Outlook for October 24-30, 2009
October 25, 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 first quarter phase on Monday October 26th. On that date the moon lies ninety degrees east of the sun and sets near 0100 local daylight time (LDT), depending on your location. As the week progresses the waxing gibbous moon sets later in the morning, lessening the window of opportunity to view meteor activity in a dark sky. The estimated total hourly rates for evening observers this week is ~5 as seen from the northern hemisphere and ~2 from the southern hemisphere. For morning observers the estimated total hourly rates should be ~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. Evening rates are reduced by moonlight.
The radiant positions and rates listed below are exact for Saturday night/Sunday morning October 24/25. 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 18:09 (272) +74. This position lies in eastern Draco near the faint star Chi 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)
The Northern Taurids (NTA) are active from a large radiant centered at 02:52 (043) +20, which lies in central Aries, five degrees west of the fourth magnitude star Delta Arietis. The radiant is best placed near 0200 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 02:58 (044) +11. This position lies on the Aries/Cetus border, three degrees east of the fourth magnitude star Mu Ceti. The radiant is best placed near the meridian at 0200 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 ~2 per hour no matter your location.
Eta Taurids (ETT)
A new radiant has been discovered in Taurus which is active during this period. The Eta Taurids (ETT) are active from October 25 through November 3, with maximum occurring on the 25th. The current radiant position lies at 03:42 (056) +24, which lies in western Taurus in the area of sky occupied by the famous Pleiades star cluster. The radiant is best placed near 0300 LDT, when it lies highest above the horizon. Meteors from the Eta Taurids strike the atmosphere at 47km/sec., which would produce meteors of average velocity. Expected rates would be < 1 per hour, no matter your location.
The Orionids (ORI) reached maximum activity on the nights of October 21 and 22. Rates are now falling and will do so until the last Orionids are seen near November 14. The radiant is currently located at 06:34 (98) +16. This position lies in western Gemini very close to the second magnitude star Alhena (Gamma Geminorum). The radiant is best placed near 0530 LDT, when it lies highest above the horizon. Current rates would be ~5 per hour. 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 occurred on the 19th. The radiant is currently located at 07:09 (107) +27. This position lies in central Gemini, three degrees south of the fourth magnitude star Tau Geminorum. This position is also close to the Orionid radiant so care must taken for correct shower association, especially since they have similar velocities. The Orionids will be more numerous. Current rates are most likely less than one 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.
Beta Cancrids (BCN)
Recent studies by Sirko Molau has revealed a radiant in Cancer that is active this time of year. The Beta Cancrids (BCN) are active from October 25 through November 3, with maximum occurring on the 27th. The current radiant position lies at 07:16 (109) -09, which lies in southwestern Canis Minor, seven degrees southwest of the brilliant zero magnitude star Procyon (Alpha Canis Minoris. The radiant is best placed near 0600 LDT, when it lies highest above the horizon.Meteors from the Beta Cancrids strike the atmosphere at 65km/sec., which would produce meteors of swift velocity. Expected rates would be < 1 per hour, no matter your location.
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 should be near one this weekend. This radiant is currently located at 10:52 (163) +36, which places it in northeastern Leo Minor, just northwest of the fourth magnitude star 46 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 ~16 Sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near ~3 per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near ~5 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 18h09m +74 28 1 1 NTA Northern Taurids 02h52m +20 29 <1 <1 STA Southern Taurids 02h58m +11 29 2 2 ETT Eta Taurids 03h42m +24 47 <1 <1 ORI Orionids 06h34m +16 67 5 5 EGE Epsilon Geminids 06h44m +28 70 <1 <1 BCN Beta Cancrids 07h16m -09 65 <1 <1 LMI Leonis Minorids 10h52m +36 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