
During this period, the moon reaches its new phase on Sunday September 21st. On that date the moon will be located near the sun and will be invisible at night. As the week progresses, the waxing crescent moon enter the evening sky but will set long before the more active morning hours arrive. The estimated total hourly rates for evening observers this weekend should be near 4 as seen from mid-northern latitudes (45N) and 3 as seen from tropical southern locations (25S). For morning observers, the estimated total hourly rates should be near 11 as seen from mid-northern latitudes (45N) and 8 as seen from tropical southern locations (25S). The actual rates seen will also depend on factors such as personal light and motion perception, local weather conditions, alertness, and experience in watching meteor activity. Note that the hourly rates listed below are estimates as viewed from dark sky sites away from urban light sources. Observers viewing from urban areas will see less activity as only the brighter meteors will be visible from such locations.
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 September 20/21. These positions do not change greatly day to day so the listed positions may be used during this entire period. Most star atlases (available online and at bookstores and planetariums) will provide maps with grid lines of the celestial coordinates so that you may find out exactly where these positions are located in the sky. I have also included charts of the sky that display the radiant positions for evening, midnight, and morning. The center of each chart is the sky directly overhead at the appropriate hour. These charts are oriented for facing south but can be used for any direction by rotating the charts to the desired direction. A planisphere or computer planetarium program is also useful in showing the sky at any time of night on any date of the year. Activity from each radiant is best seen when it is positioned highest in the sky (culmination), either due north or south along the meridian, depending on your latitude. Radiants that rise after midnight will not reach their highest point in the sky until daylight. For these radiants, it is best to view them during the last few hours before dawn. It must be remembered that meteor activity is rarely seen at its radiant position. Rather they shoot outwards from the radiant, so it is best to center your field of view so that the radiant lies toward the edge and not the center. Viewing there will allow you to easily trace the path of each meteor back to the radiant (if it is a shower member) or in another direction if it is sporadic. Meteor activity is not seen from radiants that are located far below the horizon. The positions below are listed in a west to east manner in order of right ascension (celestial longitude). The positions listed first are located further west therefore are accessible earlier in the night while those listed further down the list rise later in the night.
These sources of meteoric activity are expected to be active this week
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The last of any chi Cygnids (CCY) activity is expected early this week. The radiant should be located near 20:16 (304) +35, a position in southern Cygnus, 2 degrees east of the 4th magnitude star known as eta Cygni. These meteors can be seen all night long but are best seen near 22:00 local summer time (LST) when the radiant lies nearly overhead as seen from the northern hemisphere. Rates are expected to be low but anyone seeing any of these meteors should report them to the International Meteor Organization on their online visual meteor report form or respond to this article directly online. With an entry velocity of 15 km/sec., the average meteor from this source would be of very slow velocity. Unfortunately, these meteors are not well seen from the southern hemisphere as Cygnus does not rise high into the sky from those locations.
We are now encountering inbound debris from comet 2P/Encke, which has its source superimposed upon the anthelion radiant. Since it has been shown that meteors from 2P/Encke are more numerous than the Anthelions, we will recognize this activity as the Southern Taurids (STA) from now until late November, when we no longer encounter remnants from comet 2P/Encke. Like the anthelion radiant, the source area is large and diffuse so observers can be liberal with the shower association of these meteors. Recent investigations of the Southern Taurids have revealed two clearly distinct components. The first component, also known as the October Arietids, represents the early and annual activity of Southern Taurids. It displays very little variation year to year. The latter component represents the main source of activity and is periodic. The early STA’s are active from September 20th through November 12th and peaks on October 14th. The main component of the STA’s are active from October 13 through November 20th and peaks on November 5th. The center of the large STA radiant is currently located at 01:12 (018) +05. This position lies in southeastern Pisces, 2 degrees southeast of the 4th magnitude star known as epsilon Piscium. This radiant is best placed near 0200 LST, when it lies on the meridian and is located highest in the southern sky. Rates at this time should be near 3 per hour no matter your location. With an entry velocity of 27 km/sec., the average STA meteor would be of medium-slow velocity.
The last of the September epsilon Perseids (SPE) are expected this weekend from a radiant located at 04:00 (060) +41. This area of the sky lies in central Perseus, 1 degree north of the 3rd magnitude star known as epsilon Persei. To best see these meteors, face half-way up toward the northeast during the last hour prior to dawn. Rates at this are expected to be less than 1 no matter your location. With an entry velocity of 64 km/sec., the average meteor would be of swift velocity.
The Daytime Sextantids (DSX) are active from September 20th – October 6th, with maximum activity occurring on October 1st. The current position of the radiant is 09:56 (149) -02. This position lies in western Sextans, 3 degrees southwest of the 4th magnitude star known as alpha Sextantis. Rates at this time should be less than 1 per hour no matter your location. With an entry velocity of 32 km/sec., the average DSX meteor would be of medium-slow velocity. No matter your location, these meteors are difficult to observe as the radiant lies roughly 30 degrees from the sun. Therefore, these meteors may only be seen during the last hour prior to dawn, shooting upward from the eastern horizon.
Sporadic meteors are those meteors that cannot be associated with any known meteor shower. All meteor showers are evolving and disperse over time to the point where they are no longer recognizable. Away from the peaks of the major annual showers, these sporadic meteors make up the bulk of the activity seen each night. As seen from the mid-northern hemisphere (45N) one would expect to see during this period approximately 10 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 3 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 7 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 these listed figures.
The list below offers information in tabular form. Rates and positions in the table are exact for Saturday night/Sunday morning.
SHOWER | DATE OF MAXIMUM ACTIVITY | CELESTIAL POSITION | ENTRY VELOCITY | CULMINATION | HOURLY RATE | CLASS |
RA (RA in Deg.) DEC | Km/Sec | Local Summer Time | North-South | |||
chi Cygnids (CCY) | Sep 16 | 20:16 (304) +35 | 15 | 21:00 | <1 – <1 | III |
Southern Taurids (STA) | Nov 05 | 01:12 (018) +05 | 27 | 02:00 | 3 – 3 | II |
Sept. epsilon Perseids (SPE) | Sep 09 | 04:00 (060) +41 | 64 | 04:00 | <1 – <1 | II |
Daytime Sextantids (DSX) | Oct 01 | 09:56 (149) -02 | 32 | 11:00 | <1 – <1 | IV |
Class Explanation: A scale to group meteor showers by their intensity:
- Class I: the strongest annual showers with Zenith Hourly Rates normally ten or better.
- Class II: reliable minor showers with ZHR’s normally two to ten.
- Class III: showers that do not provide annual activity. These showers are rarely active yet have the potential to produce a major display on occasion.
- Class IV: weak minor showers with ZHR’s rarely exceeding two. The study of these showers is best left to experienced observers who use plotting and angular velocity estimates to determine shower association. These weak showers are also good targets for video and photographic work. Observers with less experience are urged to limit their shower associations to showers with a rating of I to III.