Meteor Activity Outlook for October 16-22, 2010
October 14, 2010
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 usually the big story of the month but this year the Orionid peak coincides with the full moon, which will severely reduce the number of meteors seen. Orionid activity can be seen before and after maximum when the moon is not so troublesome. Unfortunately on these nights the Orionid rates will be low, most likely less than five per hour.
During this period the moon waxes from just past its first quarter phase to nearly full at the end of the period. This weekend the waxing gibbous moon will set during the early morning hours and will allow a couple of hours of dark skies before the beginning of twilight. This window of opportunity will shrink as the week progresses becoming essentially zero by the end of the week. The estimated total hourly rates for evening observers this week is near three from the northern hemisphere and two for observers south of the equator. For morning observers the estimated total hourly rates should be near twenty four from the northern hemisphere and twelve 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 this week due to lunar interference.
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 16/17. 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)
Studies of the IMO video database by Sirko Molau and Juergen Rendtel has revealed a radiant located in Draco this time of year. Earlier visual observations placed the radiant in Ursa Minor therefore this shower is known as the October Ursa Minorids (OUI). This shower is active from October 16-28 with maximum occurring on the 24th. The moon will greatly hamper observations of this shower, especially near maximum on the 24th. On Saturday evening the radiant is located at 18:44 (281) +76. This position lies in western Draco some fifteen degrees south (above) Polaris (Alpha Ursae Minoris). Although the radiant is circumpolar (never sets) for most of the northern hemisphere, it is best placed as soon as it becomes dark. Striking the atmosphere at 28 km/sec., the average October Ursa Minorid meteor travels medium-slow through the sky. This shower is best seen from high northern latitudes. It is almost impossible to see from the southern hemisphere. Even at maximum, rates should be less than one per hour no matter your location.
Northern Taurids (NTA)
Recent studies of the IMO video database has revealed that activity from the Northern Taurids (NTA) does not begin until October 19th. This is nearly one month after pervious published 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 current radiant position lies near 02:28 (037) +18, which is located in central Aries, six degrees southeast of the second magnitude star Hamal (Alpha Arietis). The radiant is best placed near 0200 local daylight time (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 near one per hour, no matter your location.
Southern Taurids (STA)
The center of the large Southern Taurid (STA) radiant lies at 02:32 (038) +10. This position lies on the Aries/Cetus border, three degrees west of the fourth magnitude star Mu Ceti. Since the radiant is so large, any meteor from eastern Pisces, northeastern Cetus, Aries, western Taurus, or northeastern Eridanus could be a candidate for this shower. The radiant is best placed near the meridian near 0200 LDT, but activity may be seen all night long. Although maximum activity occurred on the 10th, this is a flat plateau-like peak so activity should still be good this week. Expect to see up to three Southern Taurids per hour, no matter your location, when the radiant lies highest in the sky. Striking the atmosphere at 29 km/sec., the average Southern Taurid meteor travels slowly through the skies. This shower is also responsible for many of the fireball reports seen in October.
Sigma Arietids (SSA)
Another shower derived from the IMO video database is the Sigma Arietids (SSA). This shower is active from October 12-19 with a peak on the 19th. The radiant is located at 03:16 (049) +22. This position lies in eastern Aries, four degrees northeast of the fourth magnitude star Delta Arietis. The radiant is best placed near 0300 LDT, when it lies highest above the horizon. Rates should less than one per hour. With an entry velocity of 46 km/sec., most activity from this radiant would be of medium velocity. These meteors are well seen from all but the polar regions of the Earth.
Zeta Taurids (ZTA)
Another shower derived from the IMO video database is the Zeta Taurids (ZTA). This shower is active from October 12-17 with a peak on the 16th. The radiant is located at 05:26 (081) +11. This position actually lies in Orion, three degrees northwest of the third magnitude star Lambda Orionis. The radiant is best placed near 0500 LDT, when it lies highest above the horizon. Rates should less than one per hour. With an entry velocity of 61 km/sec., most activity from this radiant would be swift. These meteors would be seen equally well from either hemisphere.
The Orionids (ORI) reach maximum activity on Friday October 22nd. Unfortunately a nearby full moon will spoil the display. The radiant is currently located at 06:08 (092) +16. This position lies in northeastern Orion, very close to the fourth magnitude star Nu Orionis. The radiant rises near 300 LDT and is best placed on the meridian near 0500. Current rates for all locations would be near three to five per hour as seen after midnight. At 67km/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 06:40 (100) +29. This position lies on the Gemini/Auriga border, four degrees northwest of the third magnitude star Mebsuta (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 probably near one per hour for the northern hemisphere and less than one as seen from south of the equator. 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 Ura Majorids (OCU)
Another shower derived from the IMO video database is the October Ursa Majorids (OCU). This shower is active from October 12-19 with a peak on the 15th. On the 12th the radiant is located at 09:52 (148) +63. This position lies in western Ursa Major, fifteen degrees west of the second magnitude star Dubhe (Alpha Ursae Majoris). The radiant is best placed during the last dark hour before dawn when it lies highest above the horizon in a dark sky. Rates should less than one per hour. With an entry velocity of 53 km/sec., most activity from this radiant would be medium-swift. With the high northern declination of the radiant, these meteors are best seen from the northern hemisphere. It would be difficult to see any of this activity from locations south of the equator.
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 less than one this week. This radiant is currently located at 10:16 (154) +35, which places it in northeastern Leo Minor, two degrees southwest 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 fifteen 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 four 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. Evening rates are reduced 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.
Shower Name RA DEC Vel Rates km/s NH SH OUI October Ursa Minorids 18h 44m +76 28 <1 <1 NTA Northern Taurids 02h 28m +18 29 1 1 STA Southern Taurids 02h 32m +10 30 3 3 SSA Sigma Arietids 03h 16m +22 46 <1 <1 ZTA Zeta Taurids 05h 26m +11 61 <1 <1 ORI Orionids 06h 08m +16 67 2 2 EGE Epsilon Geminids 06h 40m +29 70 1 <1 OCU October Ursa Majorids 09h 12m +64 53 1 <1 LMI Leonis Minorids 10h 16m +35 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