June is another slow month for meteor activity. There are no major showers active in June and only the Antihelion source can be counted on for continuous activity. Even the Antihelion radiant is located so far south this time of year that rates rarely exceed one per hour as seen from the mid-northern hemisphere (45 N) . Sporadic rates have reached their nadir and are now slowly rising as seen from the northern hemisphere. Sporadic rates seen from the mid-southern hemisphere (45 S) see a slow decline this month and a more moderate decline in July.
During this period the moon reaches its last quarter phase on Monday the 11th. At this time the moon will be located ninety degrees west of the sun and will rise near 0100 local daylight time (LDT) as seen from mid-northern latitudes. This weekend the moon will pose a problem to meteor observers but this can be overcome if you observe during the evening hours before the moon rises or face in the opposite direction if the moon lies above the horizon. Transparent skies would help immensely as moonlight would be less scattered throughout the sky. As the week progresses the waning crescent moon will become less of a problem with each passing night. The estimated total hourly meteor rates for evening observers this week is near two for observers in the northern hemisphere and three for those south of the equator. For morning observers the estimated total hourly rates should be near five as seen from mid-northern latitudes and eight from mid-southern latitudes. 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 during this period are reduced 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 June 9/10. 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 shower is expected to be active this week:
The large Antihelion (ANT) radiant is currently located at 18:12 (273) -23. This position lies in western Sagittarius, three degrees southwest of the fourth magnitude star Mu Sagittarii. Due to the large size of this radiant, Antihelion activity may also appear from eastern Scorpius, southeastern Ophiuchus, and Scutum as well as Sagittarius. This radiant is best placed near 0200 LDT, when it lies on the meridian and is located highest in the sky. Rates at this time should be near one per hour as seen from the northern hemisphere and two as seen from south of the equator. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of slow velocity.
As seen from the mid-northern hemisphere (45N) one would expect to see approximately four sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near one per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near seven per hour as seen from rural observing sites and two per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Morning 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|
|Antihelions (ANT)||-||18:12 (273) -23||30||02:00||1 – 2||II|