|Aktywność meteorowa 9-15 VI 2018
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|Autor:||Ireneusz Włodarczyk [ 08 czerwca 2018, 17:56 ]|
|Tytuł:||Aktywność meteorowa 9-15 VI 2018|
During this period the moon will reach it's new phase on Wednesday June 13th. At that time the moon will be located near the sun and will be invisible at night. This weekend the waning crescent moon will rise during the late morning hours but should not interfere with viewing meteor activity as long as you keep the moon out of your field of view. The estimated total hourly meteor rates for evening observers this week is 3 as seen from mid-northern latitude (45N) and 4 from the southern tropics (25S). For morning observers the estimated total hourly rates should be near 8 as seen from mid-northern latitudes (45N) and 11 from the southern tropics (25S). 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 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 June 09/10. 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 near 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.
The tau Herculids (TAH) may be active from a radiant located near 15:36 (234) +38. This position lies in northwestern Corona Borealis, 2 degrees northeast of the 4th magnitude star known as mu Bootis. This area of the sky is best placed as soon as it becomes dark. No activity is expected from this source this year but one might monitor this area of the sky just in case. These meteors are best suited for viewing from the northern hemisphere as the radiant is located low in the sky for observers situated in the southern hemisphere. With an entry velocity of 15 km/sec., the average tau Herculid meteor would be of very slow velocity.
The center of the large Anthelion (ANT) radiant is currently located at 18:08 (272) -23. This position lies western Sagittarius, 3 degrees southwest of the 4th magnitude star known as Polis (mu Sagittarii). Due to the large size of this radiant, Anthelion activity may also appear from southeastern Ophiuchus as well as Sagittarius. This radiant is best placed near 0200 local summer time (LST), when it lies on the meridian and is located highest in the sky. Hourly rates at this time should be near 2 as seen from mid-northern latitudes and 3 as seen from tropical southern latitudes. With an entry velocity of 30 km/sec., the average Anthelion meteor would be of slow velocity.
The Northern June Aquilids (NZC) may be seen this week from a radiant located at 19:12 (288) -11. This area of the sky is located in southern Aquila, 6 degrees south of the 3rd magnitude star known as Al Thalimain (lambda Aquilae). This radiant is best placed near 0300 LST, when it lies on the meridian and is located highest in the sky. With the July 3rd maximum still 3 weeks away, hourly rates at this time will be less than 1 no matter your location. With an entry velocity of 38 km/sec., the average meteor from this source would be of medium-slow velocity.
The June mu Cassiopeiids (JMC) were discovered by Dr, Peter Brown and associates using data from the Canadian Meteor Orbit Radar (CMOR) installation. These meteors are active from May 18-June 15, with maximum activity occurring on June 7th. The radiant position currently lies at 01:16 (019) +57. This area of the sky lies in southeastern Cassiopeia, just north of the 4th magnitude star known as Marfark (theta Cassiopeiae). These meteors are best seen near during the last dark hour of the night when the radiant lies highest in a dark sky. These meteors are better seen from the northern hemisphere where the radiant rises higher into the sky before the start of morning twilight. Hourly rates are expected to be less than 1. With an entry velocity of 42 kilometers per second, a majority of these meteors will appear to move with medium velocities.
The Daytime Arietids (ARI) are a strong shower but difficult to view due to the proximity of the radiant to the sun. These meteors are active from May 22 through June 24 with a peak on June 7. The radiant is currently located at 03:08 (047) +25. This area of the sky is located in eastern Aries, 5 degrees north of the position occupied by the 4th magnitude star known as Botein (delta Arietis). The best time to view this activity is during the hour before the start of morning twilight, when the radiant lies highest in a dark sky. With the radiant low in the east it would be best to face halfway up in the sky in a northeast direction. With an entry velocity of 42 kilometers per second, these meteors will appear to move at a medium velocity.
As seen from the mid-northern hemisphere (45N) one would expect to see approximately 5 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 2 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 3 per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Morning rates during this period are reduced due to moonlight.
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.
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
tau Herculids (TAH) Jun 02 15:36 (234) +38 15 00:00 <1 - <1 III
Anthelion (ANT) - 18:08 (272) -23 30 02:00 2 - 3 II
Northern June Aquilids (NZC) Jul 03 19:12 (288) -11 38 03:00 <1 - <1 IV
June mu Cassiopeiids (JMC) Jun 07 01:16 (019) +57 42 09:00 <1 - <1 IV
Daytime Arietids (ARI) Jun 07 03:08 (047) +25 41 11:00 1 - <1 IV
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