September offers longer nights in the northern hemisphere that tend to be less hazy than those experienced in mid-summer. In the sky, no major showers are visible from either hemisphere but the northern hemisphere enjoys the advantage of higher sporadic rates. Most of the shower activity this month is produced from the Perseus-Aurigid complex active this time of year. These showers rarely produce more than five meteors per hour but still manage to produce most of the shower activity seen this month. Unfortunately the Perseus-Aurigid complex lies too low in the northern sky for southern hemisphere observers to view very well. Video studies have shown that the Southern Taurids are visible as early as September 7th therefore after this date the Antihelion radiant will no longer be listed until the Taurid showers end in December. The Antihelion meteors are still active but their radiant is superimposed upon that of the more numerous Taurids, therefore it is impossible to properly separate these meteors. Observers in the southern hemisphere suffer from some of their lowest rates of the year this month. The Southern Taurid radiant is not too badly placed so observers south can expect to see a little of this activity this month.
During this period the moon reaches its full phase on Thursday September 23rd. At this time the moon will be located opposite the sun and will rise as the sun sets and sets as the sun rises. This weekend the waxing gibbous moon will set during the early morning hours and will allow a short window of opportunity between moonset and morning twilight to view meteor activity under dark conditions. The estimated total hourly rates for evening observers this week is near two from the northern hemisphere and one for observers south of the equator. For morning observers the estimated total hourly rates should be near sixteen from the northern hemisphere and six 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 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 September 18/19. These positions do not change greatly day to day so the listed coordinates may be used during this entire period. Most star atlases (available at science stores 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. 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, either due north or south along the meridian, depending on your latitude. It must be remembered that meteor activity is rarely seen at the radiant position. Rather they shoot outwards from the radiant so it is best to center your field of view so that the radiant lies at 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 a sporadic. Meteor activity is not seen from radiants that are located 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.
The following showers are expected to be active this week:
The center of the large Southern Taurid (STA) radiant lies at 00:56 (014) +05. This position lies in southern Pisces, three degrees southeast of the fourth magnitude star Delta Piscium. Since the radiant is so large, any meteor from Pisces, western Cetus, or southwestern Pegasus 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. Striking the atmosphere at 29 km/sec., the average Southern Taurid meteor travels slowly through the skies. Rates this week should be near two per hour no matter your location.
Many radiants in the region of Eridanus and Orion have been suspected this time of year. Recent studies have verified a radiant active in Eridanus and moving on into Orion from September 3rd through the 24th with maximum activity occurring on the 6th. The Nu Eridanid (NUE) radiant is currently located at 05:00 (075) +06. This position lies in western Orion, five degrees west of the second magnitude star Bellatrix (Gamma Orionis). Old time observers may recall a radiant active in Orion this time of year called the Sigma Orionids. This may be a verification of that activity. The radiant is best placed near 0500 LDT, when it lies highest above the horizon in a dark sky. Rates should less than one per hour this week. With an entry velocity of 68 km/sec., most activity from this radiant would be swift. With the radiant lying close to the celestial equator, these meteors are seen equally well from both hemispheres.
As seen from the mid-northern hemisphere (45N) one would expect to see approximately fourteen 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 table below presents a condensed version of the expected activity this week. Rates and positions 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 Daylight Time||North-South|
|Southern Taurids (STA)||Oct 10||00:56 (014) +05||29||02:00||2 - 2||II|
|Nu Eridanids (NUE)||Sep 06||05:00 (075) +06||68||07:00||<1 - <1||II|