October 30, 2011 2 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.
As seen from the northern hemisphere, meteor rates continue to be strong in November. While no major activity is expected this month, the two Taurid radiants plus the Leonids keep the skies active. The addition of strong sporadic rates make November one of the better months to view meteor activity from north of the equator. Skies are fairly quiet as seen from the southern hemisphere this month. Activity from the three showers mentioned above may be seen from south of the equator, but the sporadic rates are much lower than those seen in the northern hemisphere.
During this period the moon reaches its first quarter phase on Wednesday November 2nd. At this time the moon will lie ninety degrees east of the sun and will set near midnight local daylight time (LDT). This weekend the waxing crescent moon will set during the early evening hours and will not interfere with meteor observing during the more active morning hours. The estimated total hourly rates for evening observers this week is near four as seen from the northern hemisphere and three as seen from the southern hemisphere. For morning observers the estimated total hourly rates should be near eighteen as seen from mid-northern latitudes and thirteen from mid-southern latitudes. 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 moonlight.
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 29/30. 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:
The Northern Taurids (NTA) are active from a large radiant centered at 03:12 (048) +21, which lies in eastern Aries, very close to the position 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 near two per hour, no matter your location.
The center of the Southern Taurid (STA) radiant now lies 03:15 (049) +12. This position lies in southeastern Aries, eight degrees south of the fourth magnitude star Delta Arietis 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 near two per hour no matter your location.
A new radiant has been discovered in Taurus which is active during this period. The Eta Taurids (ETT) are active from October 24 through November 3, with maximum occurring on the 24th. The radiant position currently lies at 04:04 (061) +24, which lies in western Taurus, four degrees east of 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 less than one per hour, no matter your location.
The Orionids (ORI) have now passed maximum and hourly rates are now falling with each passing night. Rates are expected to be less than five per hour this week. The radiant is currently located at 06:49 (102) +16. This position lies in southern Gemini, two degrees southeast of the second magnitude star Alhena (Gamma Geminorum). The radiant is best placed near 0500 LDT, when it lies highest above the horizon. At 67km/sec., the average Orionid is swift.
Recent studies by Sirko Molau and Juergen Rendtel have revealed a radiant in Canis Minor that is active this time of year. Old radiant positions placed it within the borders of Cancer. The Beta Cancrids (BCN) are active from October 25 through November 3, with maximum occurring on the 27th. The radiant position currently lies at 07:32 (113) -03, which lies in central Canis Minor, five degrees south 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 less than one per hour, no matter your location.
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 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 NTA Northern Taurids 03h 12m +21 29 2 2 STA Southern Taurids 03h 15m +12 27 2 2 ETT Eta Taurids 04h 04m +24 47 <1 <1 ORI Orionids 06h 49m +16 61 3 3 BCN Beta Cancrids 07h 32m -03 65 <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