November 26, 2012 Leave a comment
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 full phase on Wednesday November 28th. At this time the moon is located opposite the sun and will remain in the sky all night long. This weekend the waxing gibbous moon will set during the early morning hours and will allow a couple of hours between moon set and morning twilight to view the meteor activity under good conditions. The estimated total hourly meteor rates for evening observers this week is near three for observers located at mid-northern latitudes and two for observers in mid-southern latitudes. For morning observers the estimated total hourly rates should be near eighteen from the mid-northern hemisphere and ten from the mid-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. Rates are reduced during this period 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 November 24/25. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.
The following radiants are expected to be active this week:
Remnants from the famous Andromedid (AND) shower, noted for intense storms during the 19th century, may still be seen throughout November. The current position of this large radiant is 01:38 (024) +41. This position lies in eastern Andromeda, close to the position occupied by the faint stat known as Upsilon Andromedae. The radiant is so diffuse that Andromedid meteors may be seen coming from Triangulum, northern Pisces, as well as Andromeda. Visual activity is expected to be low, but detectable. An inconspicuous maximum occurred on November 9, when this source was the 5th most active radiant in the sky. The Andromedid meteors are best seen near 2200 (10pm) local standard time (LST), when the radiant lies on the meridian and lies highest in the sky. At 19km/sec., the average Andromedid will appear as a very slow moving meteor.
Studies of the IMO video database by Sirko Molau and Juergen Rendtel has revealed another active radiant in Taurus this time of year. Now that the Southern Taurids are no longer detectable, the Gamma Taurids (GTA) may be distinguished within the Taurid complex. The Gamma Taurid radiant is centered at 04:22 (065) +15. This area of the sky lies in western Taurus, three degrees southwest of the orange first magnitude star Aldebaran (Alpha Tauri). The radiant is best placed near 0100 LST, when it lies highest above the horizon. Maximum activity occurred on November 10th so current rates would be near one shower member per hour, no matter your location. Meteors from the Gamma Taurids strike the atmosphere at 27km/sec., which would produce meteors of slow velocity.
The Northern Taurids (NTA) are active from a radiant centered at 04:40 (070) +25. This area of the sky lies in northern Taurus, nine degrees north of the orange first magnitude star Aldebaran (Alpha Tauri). The radiant is best placed near 0100 LST, when it lies highest above the horizon. Maximum activity occurred on November 13th so current hourly rates would be near two from the northern hemisphere and one from south of the equator. Meteors from the Northern Taurids strike the atmosphere at 29km/sec., which would produce meteors of slow velocity.
The November Orionids (NOO) are now the most active radiant in the sky and will remain #1 throughout the remainder of November. This radiant is located at 05:50 (087) +15. This area of the sky is located on the Orion/Taurus border, eight degrees north of the first magnitude orange star Betelgeuse (Alpha Orionis). The peak occurs on November 30th so current rates will be 2-3 per hour, no matter your location. If the moon lies above the horizon rates will be lower due to the lunar glare. The radiant is best placed for viewing near 0200 LST when it lies on the meridian and is highest above the horizon. With an entry velocity of 44 km/sec., the November Orionids would be of medium speed.
The Leonids (LEO) are still active from a radiant located at 10:34 (159) +20. This position lies in northwestern Leo, two degrees east of the second magnitude double star Algeiba (Gamma Leonis). Current rates should be 1-2 per hour, no matter your location. The Leonid radiant is best placed during the last hour before morning twilight when the radiant lies highest in a dark sky. Leonids may be seen from the southern hemisphere but the viewing conditions are not quite as favorable as those north of the equator.
Studies of the IMO video database by Sirko Molau and Juergen Rendtel has revealed an active radiant in Draco this time of year. The November Iota Draconids (NID) radiant is located at 12:44 (191) +68. This area of the sky lies in western Draco, two degrees southeast of the fourth magnitude star Kappa Draconis. The radiant is best placed near 0100 LST, when it lies highest above the horizon. Maximum activity occurs on November 26th so current rates would be less than one shower member per hour, no matter your location. Due to the high northerly declination of the radiant these meteors are not visible from most of the southern hemisphere. Only southern equatorial regions would have any chance of seeing activity from this source Meteors from the November Iota Draconids strike the atmosphere at 43km/sec., which would produce meteors of medium velocity.
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. 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 but may be used
for the entire period.
Andromedids (AND) – 01:38 (024) +41 Velocity – 19km/sec.
Northern Hemisphere – <1 per hr. Southern Hemisphere – <1 per hr.
Gamma Taurids (GTA) – 04:22 (065) +15 Velocity – 29km/sec.
Northern Hemisphere – 1 per hr. Southern Hemisphere – 1 per hr.
Northern Taurids (NTA) – 04:40 (070) +25 Velocity – 29km/sec.
Northern Hemisphere – 2 per hr. Southern Hemisphere – 1 per hr.
November Orionids (NOO) – 05:50 (087) +15 Velocity – 44km/sec.
Northern Hemisphere – 3 per hr. Southern Hemisphere – 2 per hr.
Leonids (LEO) – 10:34 (159) +20 Velocity – 71km/sec.
Northern Hemisphere – 2 per hr. Southern Hemisphere – 1 per hr.
November Iota Draconids (NID – 12:44 (191) +68 Velocity – 43km/sec.
Northern Hemisphere -<1 per hr. Southern Hemisphere – <1 per hr.
American Meteor Society