Meteor Activity Outlook for October 10-16, 2009
October 12, 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 last quarter phase on Sunday October 11th. At this time the moon rises near 0100 local daylight time (LDT) and remains in the sky the remainder of the night. The situation improves as the week progresses with the moon waning into a crescent phase and rising later in the night with each passing morning. The estimated total hourly rates for evening observers this week is ~4 as seen from the northern hemisphere and ~2 from the southern hemisphere. For morning observers the estimated total hourly rates should be ~15 from the northern hemisphere and ~10 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. Morning rates are reduced by moonlight.
The radiant positions and rates listed below are exact for Saturday night/Sunday morning October 10/11. 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.
A recent study of video radiants by Sirko Molau has revealed a radiant in Pisces active from October 7-11. Maximum activity occurs on the 9th from a radiant located at 0:05 (001) +14. This position is located on the Pisces/Pegasus border, three degrees southwest of the 3rd magnitude star Algenib (Gamma Pegasi). The radiant is best placed near 0100 LDT, when it lies highest above the horizon. Meteors from the October Epsilon Piscids (OPC) strike the atmosphere at only 19km/sec., which would produce slow moving meteors. Expected rates would be < 1 per hour, no matter your location.
The center of the large Southern Taurid (STA) radiant lies at 02:10 (032) +09. This position lies on the Pisces/Cetus border, one degree west of the fourth magnitude star Xi Ceti. Since the radiant is so large, any meteor from eastern Pisces, northern Cetus, or southwestern Aries could be a candidate for this shower. 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 ~3 per hour no matter your location.
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 02:52 (043) +22, which lies in eastern Aries, six degrees south of the faint star 41 Arietis. The radiant is best placed near 0300 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.
Another new radiant has been discovered in Taurus which is active during this period. The Zeta Taurids (ZTA) are active from October 12-17, with maximum occurring on the 16th. The current radiant position lies at 05:06 (076) +15, which lies on the Taurus/Orion border, six degrees east of the bright first magnitude orange star Aldebaran (Alpha Tauri). The radiant is best placed near 0500 LDT, when it lies highest above the horizon. Meteors from the Zeta Taurids strike the atmosphere at 61km/sec., which would produce meteors of swift velocity. Expected rates would be < 1 per hour, no matter your location.
The Orionids (ORI) are now becoming more active from a radiant located at 05:50 (87) +15. This position lies on the Orion/Taurus border, seven degrees north of the orange first magnitude star Betelgeuse (Alpha Orionis). The radiant rises near 2300 LDT and is best placed on the meridian near 0600. With maximum activity predicted for October 22, current rates for all locations would be ~2-3 per hour as seen after midnight. At 66km/sec., the average Orionid is swift.
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 09:12 (138) +63, which lies in western Ursa Major, two degrees west of the faint star 23 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 less than one per hour, no matter your location. This
activity is not visible from the southern hemisphere due to the high northerly declination of the radiant.
As seen from the mid-northern hemisphere (45N) one would expect to see ~8 Sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near four per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near two 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. 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 OPC Oct ε-Piscids 00h05m +14 19 <1 <1 STA Southern Taurids 02h10m +09 29 3 3 SSA Sigma Arietids 02h52m +22 45 <1 <1 ZTA Zeta Taurids 05h06m +15 61 <1 <1 ORI Orionids 05h50m +15 67 3 3 OCU Oct. Ursa Majords 09h12m +63 53 <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