During this period the moon reaches its new phase on Saturday July 26th. At this time the moon will located near the sun and will be invisible at night. Later this week the waxing crescent moon will enter the evening sky but will set during the evening hours. The more active morning hours will not be affected by moonlight. The estimated total hourly meteor rates for evening observers this week is near 4 as seen from the northern hemisphere and 3 as seen from southern tropical latitudes. For morning observers the estimated total hourly rates should be near 30 no matter your location. 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. 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 brightest 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 July 26/27. 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.
These sources of meteoric activity are expected to be active this week:
The Gamma Draconids (GDR) were discovered by members of SonotaCo during their study of video radiants in 2007 and 2008. This is a weak, short-lived display with activity limited to July 24-31. Maximum activity occurs on the 28th when rates may approach 1 meteor per hour. The radiant location at maximum is 18:42 (281) +51, which places it in southern Draco, 8 degrees west of the 2nd magnitude star Eltanin (Gamma Draconis). Activity from this source is best seen near 2200 (10pm LDT) when it lies highest in the sky. These meteors are poorly seen from the southern hemisphere due to a lower radiant altitude. With an entry velocity of 27 km/sec., the average Gamma Draconid meteor would be of slow velocity.
The Alpha Capricornids (CAP) are active for over a month lasting from July 6 through August 10. Unlike most showers, the Alpha Caps have a plateau-like maximum with maximum activity lasting from July 25-30. The radiant is currently located at 20:20 (305) -11. This area of the sky is located in northwestern Capricornus, just north of the naked eye double known as Algiedi (Alpha Capricornii). The radiant is best placed near midnight local daylight time (LDT) when it lies on the meridian and is highest in the sky. Rates this weekend should be near 3 per hour no matter your location. While most members of the Alpha Caps are faint, this shower has been know to produce fireballs so don’t be surprised to witness an extraordinarily bright meteor from this source. With an entry velocity of 22 km/sec., the average Alpha Capricornid meteor would be of slow velocity. Please note that with this radiant and the Anthelions are located in the same area of the sky. The only way to properly differentiate between them would be to have both radiants included within your field of view. Even then it could be difficult as any potential meteor could trace back to more than 1 radiant area, especially since the sizes of the CAP’s and ANT’s are larger than normal.
The center of the large Anthelion (ANT) radiant is currently located at 21:08 (317) -16. This position lies in north-central Capricornus, very close to the 4th magnitude star known as Dorsum (Theta Capricorni). These meteors may be seen all night long but the radiant is best placed near 0100 LDT when it lies on the meridian and is positioned highest in the sky. Due to the large radiant area, meteors from this source may also appear to radiant from the constellation of Microscopium, eastern Sagittarius, southeastern Aquila, Aquarius, and western Pisces Austrinus as well as Capricornus. Rates at this time should be near 2 per hour no matter you location. With an entry velocity of 30 km/sec., the average Anthelion meteor would be of slow velocity.
The Delta Aquariids (SDA) will reach maximum activity on Wednesday morning July 30, from a radiant located at 22:42 (340) -16. This position is located in southern Aquarius, 3 degrees west of the third magnitude star known as Skat (Delta Aquarii). Hourly rates at maximum will depend on your latitude. Those viewing from the southern tropics will see the best rates of near 20-30 per hour. Rates seen from mid-northern latitudes will range from 5-15 per hour, depending on the haziness of your skies. Note that these rates will only be seen under very dark skies in rural locations during the late morning hours when the radiant lies highest above the horizon. The radiant rises near 2200 (10pm) LDT for observers located in the mid northern latitudes, but is best placed near 0300 LDT, when it lies highest in the sky. With an entry velocity of 42 km/sec., most activity from this radiant would be of average velocities.
The Piscids Austrinids (PAU) are a minor shower not well seen from the northern hemisphere. This radiant is active from July 15 through August 10. Maximum activity occurs on July 28 when the zenith hourly rate (ZHR) may reach five. These rates are only seen from the southern hemisphere where the radiant passes overhead. From mid-northern latitudes, rates of one per hour at maximum are usually seen. The radiant is currently located at 22:44 (341) -32. This position lies in eastern Piscis Austrinus, 4 degrees southwest of the bright first magnitude star Fomalhaut (Alpha Piscis Austrinus). The radiant is best placed near 0300 LDT, when it lies highest in the sky. With an entry velocity of 35km/sec., most activity from this radiant would be of average velocities.
Recent information from the multi-station Canadian Meteor Orbit Radar website indicates that there is an active radiant just north of Cassiopeia. They indicate that this activity is from the Psi Cassiopeiids (PCA). Yet information provided by the IMO on this shower indicates that activity from this source ended on July 18. The position of the radiant also does not match that of the PCA’s, even if stretched to the current date. Regardless, it may be an interesting project to monitor activity from the Cassiopeia area and try to verify any activity. Any activity from this area of the sky would be fairly swift and best seen during the late morning hours before dawn.
The Perseids (PER) are active from a radiant located at 01:36 (024) +53. This position lies in extreme western Perseus, 4 degrees southeast of the 4th magnitude star known as Marfark (Theta Cassiopeiae). The radiant is best placed during the last hour before the start of morning twilight when it lies highest in a dark sky. Since the maximum is not until August 13th, current rates would be only near 5 per hour at best, as seen from the northern hemisphere. Activity from this source is not visible south of 40 degrees south latitude. With an entry velocity of 61 km/sec., most activity from this radiant would be swift with a large percentage of persistent trains produced by the brightest meteors.
The Alpha Triangulids (ATR) are now active from a radiant located at 02:07 (032) +41. This position actually lies in eastern Andromeda just southeast of the famous bright double star known as Almach (Gamma Andromedae). This source of meteors is best seen from July 25 through August 20 with maximum activity occurring on July 27. Hourly rates at maximum should range from 2 as seen from the northern hemisphere to near 1 as seen south of the equator. The radiant is best placed during the last hour before the start of morning twilight when it lies highest in a dark sky. With an entry velocity of 68 km/sec., most activity from this radiant would be swift.
Activity from the Eta Eridanids (ERI) should begin this week. This shower is best seen from July 31 through August 17 with maximum activity occurring on August 4. The radiant is currently located at 02:08 (032) -16. This location actually lies in southeastern Cetus, 5 degrees southwest of the 4th magnitude star known as Pi Ceti. Hourly rates should be near 3 as seen from the southern hemisphere and 2 as seen from north of the equator. The radiant is best placed during the last hour before the start of morning twilight when it lies highest in a dark sky. With an entry velocity of 66 km/sec., most activity from this radiant would be swift.
As seen from the mid-northern hemisphere (45N) one would expect to see approximately 11 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 9 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 list of radiants that are expected to be active this week. Rates and positions are exact for Saturday night/Sunday morning except where noted in the shower descriptions.
|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|
|Gamma Draconids (GDR)||Jul 28||18:42 (281) +51||27||22:00||<1 – <1||IV|
|Alpha Capricornids (CAP)||Jul 27||20:20 (305) -11||22||00:00||3 – 3||II|
|Anthelions (ANT)||–||21:08 (317) -16||29||01:00||2 – 2||II|
|Delta Aquariids (SDA)||Jul 30||22:42 (340) -16||42||03:00||5 – 8||I|
|Piscids Austrinids (PAU)||Jul 28||22:44 (341) -32||35||03:00||1 – 2||II|
|Perseids (PER)||Aug 13||01:36 (024) +53||61||06:00||5 – 3||I|
|Alpha Triangulids (ATR)||Jul 27||02:07 (032) +41||68||07:00||2 – 1||IV|
|Eta Eridanids (ERI)||Aug 04||02:08 (032) -16||66||07:00||2 – 3||IV|