Meteor Activity Outlook for November 21-27, 2009
November 19, 2009 55 Comments
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.
As seen from the northern hemisphere, meteor rates continue to be strong in November. While no major showers are active 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 Tuesday November 24th. On that date the moon lies ninety degrees east of the sun and will set near midnight local standard time (LST). This weekend the waxing crescent moon will set long before the more active morning hours arrive, allowing dark skies for those who venture out during the morning hours. As the week progresses the moon sets later each night narrowing the window of opportunity to view under dark conditions. The estimated total hourly rates for evening observers this week is near four as seen from the northern hemisphere and three from the southern hemisphere. For morning observers the estimated total hourly rates should be near twenty from the northern hemisphere and ten 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. Rates are reduced during the evening hours due to moonlight.
The radiant positions and rates listed below are exact for Saturday night/Sunday morning November 21/22. 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.
Sirko Molau’s studies of video radiants has revealed that activity from the famous Andromedid shower, noted for intense storms during the 19th century, may still be seen throughout November. This position lies in eastern Andromeda, two degrees south of the fourth magnitude star Nu Andromedae. The nearest bright star is second magnitude Almach (Gamma Andromedae), which lies four degrees to the northeast. Visual activity is expected to be low, but detectable. The Andromedid radiant is best placed near 2200 (10pm) local standard time (LST) when it lies on the meridian. At 19km/sec., the average Andromedid will appear as a very slow moving meteor. Sirko mentions that these meteors are “conspicuously slow and of almost constant activity” during this period.
Northern Taurids (NTA)
The Northern Taurids (NTA) are active from a large radiant centered at 04:29 (067) +24, which lies in northern Taurus, eight 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, but activity may be seen all night long. Meteors from the Northern Taurids strike the atmosphere at 29km/sec., which would produce meteors of slow velocity. Expected rates would be ~3 per hour as seen from the northern hemisphere and ~2 per hour as seen south of the equator.
November Orionids (NOO)
The November Orionids (NOO) were recently discovered by analyzing video data. This shower is active from November 18 through December 9. Maximum activity occurs on November 30. The radiant is currently (11/18) located at 05:44 (086) +15. This position lies on the Orion/Taurus border, six degrees north of the third magnitude star Lambda Orionis. These meteors are also best seen near 0300 LST when the radiant lies on the meridian and highest above the horizon. At 44 km/sec. the November Orionids produce mostly medium velocity meteors.
Alpha Monocerotids (AMO)
The Alpha Monocerotids (AMO) are active from November 15-25, with maximum occurring on the 21st. This shower has produced outbursts in the past but none are expected for many years to come. Rates are expected to be < 1 shower member per hour, even on the night of maximum activity. The radiant is currently located at 07:52 (118) +01. This position lies in southeastern Canis Minor, five degrees southeast of the zero magnitude star Procyon (Alpha Canis Minoris). These meteors are also best seen near 0500 LST when the radiant lies highest above the horizon in a dark sky. At 65 km/sec. the Alpha Monocerotids produce mostly swift meteors.
The Leonids (LEO) reached maximum activity on the morning of November 17th with ZHR’s exceeding 100 as seen over Asia. Current rates would be near one per hour no matter your location. The radiant is currently located at 10:27 (157) +20. This position lies in western Leo, just one degree northeast of the famous second magnitude double star Algeiba (Gamma Leonis). At 70km/sec., the average Leonid is swift with a high percentage of trains. The radiant does not rise until the late evening hours so it is advised to wait until after midnight before beginning serious observations. The radiant is most favorably located during the last dark hour before the onset of morning twilight when it lies highest in a dark sky.
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 ~3 per hour. As seen from the mid-southern hemisphere (45S), morning rates would be ~6 per hour as seen from rural observing sites and ~2 per hour during the evening hours. Locations between these two extremes would see activity between the listed figures.
The table 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 all week long.
Shower Name RA DEC Vel Rates km/s NH SH AND Andromedids 01h 38m +39 19 <1 <1 NTA Northern Taurids 04h 29m +24 29 3 2 AMO Alpha Monocerotids 07h 52m +01 65 <1 <1 LEO Leonids 10h 27m +20 70 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