Meteor Activity Outlook for 12-18 August 2017

During this period the moon will reach its last quarter phase on Tuesday August 15. At this time the moon will be located 90 degrees west of the sun and will rise near midnight local summer time (LST). This weekend the waning gibbous moon will rise during the late evening hours and will illuminate the sky for the remainder of the night, reducing the number of meteors seen. The estimated total hourly meteor rates for evening observers this week is near 6 for those viewing from the northern hemisphere and 3 for those located south of the equator. For morning observers the estimated total hourly rates should be near 32 as seen from mid-northern latitudes and 16 from the southern tropics. 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. Morning rates are reduced during this period due to interfering moonlight. 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 August 12/13. 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 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 August Draconids (AUD) were discovered by Zdenek Sekanina in his study of meteor streams using radio methods. This stream is active from August 13-19 with maximum activity occurring on the 16th. The radiant is currently located at 18:04 (271) +59, which places it in southern Draco, 8 degrees north of the 2nd magnitude star known as Eltanin (gamma Draconis). This radiant is best placed near 2200 LST, when it lies on the meridian and is located highest in the sky. With an entry velocity of 21 km/sec., the average August Draconid meteor would be of slow velocity. Rates this week are expected to be less than 1 per hour no matter your location

The kappa Cygnids (KCG) are one of the few meteor showers best seen during the evening hours. This stream is active from August 8-17 with maximum activity occurring on the 13th. The radiant is currently located at 19:00 (285) +50, which places it in extreme southeastern Draco between the bright stars Eltanin (gamma Draconis) and delta Cygni. The radiant also lies 10 degrees northeast of the brilliant zero magnitude star Vega (alpha Lyrae). This radiant is best placed near 2300 LST, when it lies on the meridian and is located highest in the sky. With an entry velocity of 21 km/sec., the average kappa Cygnid meteor would be of slow velocity. Rates this weekend are expected to be near 1 per hour as seen from the northern hemisphere and less than 1 as seen from south of the equator.

The center of the large Anthelion (ANT) radiant is currently located at 22:12 (333) -11. This position lies in western Aquarius, 3 degrees south of the 4th magnitude star known as Ancha (theta Aquarii). Due to the large size of this radiant, Anthelion activity may also appear from eastern Capricornus as well as Aquarius. This radiant is best placed near 0200 LST, when it lies on the meridian and is located highest in the sky. Hourly rates at this time should be near 1 as seen from mid-northern latitudes and 2 as seen from tropical southern latitudes. With an entry velocity of 30 km/sec., the average Anthelion meteor would be of medium-slow velocity.

The Northern delta Aquariids (NDA) are active from July 23 through August 27. The radiant is currently located at 23:04 (346) +02. This position is located in western Pisces, just west of the group of faint stars known as the “Circlet”. Hourly rates should be near 1 per hour no matter your location. The radiant is best placed near 0300 LST, when it lies highest in the sky. With an entry velocity of 38 km/sec., these meteors would be of medium velocities. This shower seems to be a continuation of the Northern June Aquilids, which had been active since early June.

The Southern Delta Aquariids (SDA) reach maximum activity on July 30 from a radiant located at 23:36 (354) -11. This position is located in eastern Aquarius, 4 degrees southeast of the group of faint stars known as psi Aquarii. Hourly rates will range from 1 per hour as seen from the northern hemisphere to 2 as seen from south of the equator. The radiant is best placed near 0400 LST, when it lies highest in the sky. With an entry velocity of 41 km/sec., most activity from this radiant would be of average velocities.

The Piscids Austrinids (PAU) are an obscure shower, not well seen from the northern hemisphere. Recent studies by the IMO Video Network shows no activity at all. Other studies have indicated that this shower is active later than previously thought. We will go along with that idea until more information is available. It is now thought that this radiant is active from July 30 through August 18, with maximum activity occurring on the 8th. Using these parameters, the current position of the radiant would be 23:48 (357) -19. This area of the sky is located in southern Aquarius, 12 degrees northeast of the bright 1st magnitude star known as Fomalhaut (alpha Piscis Austrini). The radiant is best placed near 0400 LST, when it lies highest in the sky. Current rates would most likely be less than 1 per hour, no matter your location. With an entry velocity of 44km/sec., most activity from this radiant would be of average velocities.

The beta Hydrusids (HDY) are only known through an outburst reported on August 17, 1985. Activity from this stream is seen from August 15-19 with maximum activity occurring on the 17th. At maximum the radiant lies at 02:25 (036) -75, which places it in southern Hydrus between the bright stars known as beta and gamma Hydri. Due to the far southern location, these meteors are not visible from the northern hemisphere. For southern observers, this area of the sky is best seen during the last dark hour before dawn when the radiant lies highest in a dark sky. Current rates are expected to be less than 1 per hour during this period no matter your location. With an entry velocity of 23 km/sec., the average meteor from this source would be of slow velocity.

The eta Eridanids (ERI) were discovered by Japanese observers back in 2001. Activity from this stream is seen from July 23 though September 17 with maximum activity occurring on August 11. The radiant currently lies at 03:04 (046) -12, which places it in western Eridanus, 4 degrees southeast of the 4th magnitude star known as eta Eridani. This area of the sky is best seen during the last dark hour before dawn when the radiant lies highest in a dark sky. Current rates are expected to be near 1 per hour during this period no matter your location. With an entry velocity of 65 km/sec., the average meteor from this source would be of swift velocity.

The Perseids (PER) are active from a radiant located at 03:12 (048) +58. This position lies close to the area where the borders of Perseus, Cassiopeia, and Camelopardalis meet. The 4th magnitude star known as eta Persei lies 4 degrees to the southwest. This area of the sky is best placed for viewing during the last dark hour before dawn when it lies highest in the sky. Rates will be strong (~20 per hour) this weekend as seen from the northern hemisphere. Rates seen from the southern hemisphere are expected to be less than 5 per hour. These rates will decrease by 50% each night as we pass the date of maximum. With an entry velocity of 59 km/sec., the average meteor from this source would be of swift velocity.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately 7 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 4 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 5 per hour as seen from rural observing sites and 2 per hour during the evening hours. Morning rates are reduced during this period due to moonlight. Locations between these two extremes would see activity between the listed figures.

The list below offers the information from above in tabular form. Rates and positions are exact for Saturday night/Sunday morning except where noted in the shower descriptions.