|Aktywność meteorowa 12-18 I 2019
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|Autor:||Ireneusz Włodarczyk [ 13 stycznia 2019, 07:44 ]|
|Tytuł:||Aktywność meteorowa 12-18 I 2019|
During this period the moon will reach its first quarter phase on Monday January 14th. At this time the moon will be located 90 degrees east of the sun and will set near midnight local standard time (LST) as seen from mid-northern latitudes. As the week progresses the waxing gibbous moon will set later in the morning, encroaching on the more active morning hours. Hourly meteor rates for evening observers this week is near 3 as seen from mid-northern latitudes (45N) and 2 as seen from tropical southern locations (25S). For morning observers the estimated total hourly rates should be near 12 as seen from mid-northern latitudes and 10 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. Evening rates are reduced 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 January 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 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.
Now that the activity from particles produced by comet 2P/Encke have ceased encountering the Earth, the Taurid showers are over and we resume reporting activity from the Anthelion (ANT) radiant. This is not a true radiant but rather activity caused by the Earth's motion through space. As the Earth revolves around the sun it encounters particles orbiting in a pro-grade motion that are approaching their perihelion point. They all appear to be radiating from an area near the opposition point of the sun, hence the name Anthelion. These were once recorded as separate showers throughout the year but it is now suggested to bin them into their category separate from true showers and sporadics. There are several lists that have the delta Cancrids currently active, but we include them with the Anthelions as the celestial positions overlap. This radiant is a very large oval some thirty degrees wide by fifteen degrees high. Activity from this radiant can appear from more than one constellation. The position listed here is for the center of the radiant which is currently located at 08:20 (125) +20. This position lies in western Cancer, 6 degrees northwest of the 4th magnitude star known as Asellus Australis (delta Cancri). Since the radiant is so large, Anthelion activity may also appear from eastern Gemini as well as Cancer. This radiant is best placed near 01:00 LST when it lies on the meridian and is highest in the sky. Rates at this time should be near 2 per hour as seen from the northern hemisphere and 1 per hour as seen from south of the equator. With an entry velocity of 30 km/sec., the average Anthelion meteor would be of slow velocity.
The alpha Hydrids (AHY) were discovered by Dr. Peter Brown and are mentioned in his article "A meteoroid stream survey using the Canadian Meteor Orbit Radar". This shower is active from December 17 through January 17 with maximum activity occurring on January 3rd. The radiant is currently located at 09:02 (136) -11. This position lies in southwestern Hydra, 5 degrees southwest of the 2nd magnitude star known as Alphard (alpha Hydrae). These meteors are best seen near 0200 LST when the radiant lies highest above the horizon. At 43 km/sec. the alpha Hydrids produce meteors of medium velocity. Expected rates this week are less than 1 per hour no matter your location.
The January xi Ursae Majorids (XUM) is a shower discovered by Japanese observers of SonotoCo based on video observations in 2007-2008. This shower is active from January 15-22, with maximum activity occurring on the 18th. At maximum the radiant is located at 11:15 (169) +33, which lies in southwestern Ursa Major, just west of the 3rd magnitude star known as Alula Borealis (xi Ursae Majoris). These meteors are best seen near 04:00 LST when the radiant lies highest above the horizon. Hourly rates should be near 1 as seen from the northern hemisphere and less than 1 as seen south of the equator. These meteors encounter the atmosphere at 41 km/sec., which would produce meteors of average velocity.
The December Leonis Minorids (DLM) are a shower of long duration active from December 6th through January 18th. Maximum occurs near December 21st when rates may reach 3 an hour. Current rates are likely less than 1 per hour no matter your location. The radiant is currently located at 12:03 (181) +21. This position lies in western Coma Berenices, 7 degrees northeast of the 2nd magnitude star known as Denebola (beta Leonis). These meteors are best seen near 0400 LST when the radiant lies highest above the horizon. At 63 km/sec. the December Leonis Minorids produce mostly swift meteors.
The eta Corvids (ECV) were recently discovered by Sirko Molau and the IMO Video Meteor Network Team. This stream is active from January 16-29, with maximum activity occurring on the 22nd. The current position of the radiant is 12:16 (184) -14, which places the radiant in northern Corvus, 4 degrees northwest of the 3rd magnitude star known as Algorab (delta Corvi). These meteors are best seen near 0400 LST when the radiant lies highest above the horizon. Current hourly rates would be less than 1 per hour no matter your location. At 68 km/sec. these meteors would be fast.
The lambda Bootids (LBO) were discovered by Dr. Peter Brown and his team at the University of Western Ontario, London, Ontario, Canada. They were using radio means to discover new streams. These meteors are active from December 31 through January 17 with maximum activity occurring on the 16th. The radiant currently lies at 14:34 (218) +45. This position lies in northwestern Bootes, 4 degrees southeast of the 4th magnitude star known as Xuange (lambda Bootis). Current rates are expected to be near 1 per hour as seen from the northern hemisphere. Rates would be less than 1 per hour for observers located in the southern hemisphere. At 41 km/sec. these meteors are of medium velocity.
The gamma Ursae Minorids (GUM) were also discovered by Dr. Peter Brown and associates. These meteors are active from January 09-20, with maximum occurring on the 18th. The radiant is currently located at 15:08 (228) +71, which places it southern Ursa Minor, 2 degrees south of the 3rd magnitude star known as Pherkad (gamma Ursae Minoris). These meteors are best seen during the last few hours before dawn, when the radiant lies highest in a dark sky. Expected rates are less than 1 per hour during this period no matter your location. These meteors encounter the atmosphere at 30 km/sec., which would produce meteors of medium-slow velocity.
As seen from the mid-northern hemisphere (45N) one would expect to see approximately 9 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 9 per hour as seen from rural observing sites and 2 per hour during the evening hours.
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 Standard Time North-South
Anthelion (ANT) - 08:20 (125) +20 30 01:00 2 - 1 II
alpha Hydrids (AHY) Jan 03 09:02 (136) -11 43 02:00 <1 - <1 IV
January xi Ursae Majorids (XUM) Jan 18 11:15 (169) +33 41 04:00 1 - <1 IV
December Leonis Minorids (DLM) Dec 21 12:03 (181) +21 63 05:00 <1 - <1 II
eta Corvids (ECV) Jan 22 12:16 (184) -14 68 05:00 <1 - <1 IV
lambda Bootids (LBO) Jan 16 14:34 (218) +45 41 07:00 <1 - <1 IV
gamma Ursae Minorids (GUM) Jan 18 15:08 (228) +71 30 08:00 <1 - <1
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