|Aktywność meteorowa 19 - 25 XII 2020
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|Autor:||Ireneusz Włodarczyk [ 19 grudnia 2020, 07:04 ]|
|Tytuł:||Aktywność meteorowa 19 - 25 XII 2020|
During this period, the moon reaches its first quarter phase on Tuesday December 22nd. At this time, the moon is located 90 degrees east of the sun and will set near midnight local standard time. This weekend the waxing crescent moon will set during the evening hours and will not interfere with viewing the stronger meteor activity that occurs during the morning hours. The estimated total hourly meteor rates for evening observers this week is near 3 as seen from mid-northern latitudes and 3 as seen from tropical southern locations (25S). For morning observers, the estimated total hourly rates should be near 18 as seen from mid-northern latitudes (45N) and 14 as seen from tropical southern locations (25S). Evening rates are reduced during this period due to moonlight. 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 December 19/20. 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 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.
Radiant Positions at 18:00 LST
Radiant Positions at 18:00 Local Standard Time
Radiant Positions at 00:00 LST
Radiant Positions at 00:00 Local Standard Time
Radiant Positions at 06:00 LST
Radiant Positions at 06:00 Local Standard Time
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 for 2020 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 a category separate from true showers and sporadics. 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 06:44 (101) +23. This position lies in central Gemini, 2 degrees south of the 3rd magnitude star known as Mebsuta (epsilon Geminorum). Since the radiant is so large, Anthelion activity may also appear from southeastern Auriga, eastern Taurus, and northeastern Orion as well as Gemini. This radiant is best placed near 01:00 local standard time (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 December Monocerotids (MON) are active from November 18th through December 26th with the peak activity occurring on December 13th. The radiant is currently located at 07:10 (108) +07. This position lies on the border of Canis Minor and Monoceros, 5 degrees southwest of the 3rd magnitude star known as Gomeisa (beta Canis Minoris). Current rates should be near 1 per hour no matter your location. Monocerotids are best seen near 0200 LST when the radiant lies highest above the horizon. At 39 km/sec. the Monocerotids produce mostly meteors of medium 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 5th. The radiant is currently located at 07:50 (117) -06. This position lies in eastern Monoceros, 4 degrees northeast of the 4th magnitude star known as alpha Monocerotis. This location is also 10 degrees southeast of the brilliant zero magnitude star known as Procyon (alpha Canis Minoris). These meteors are best seen near 0200 LST when the radiant lies highest above the horizon. At 45 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 last of the Geminids (GEM) will be seen this week from a radiant is located at 08:02 (121) +31. This position lies in northeastern Gemini, 5 degrees northeast of the 1st magnitude star known as a Pollux (beat Geminorum). Rates this weekend should be less than 1 per hour no matter your location. This radiant is best placed in the sky near 0200 LST, when it lies highest above the horizon. At 34 km/sec. the Geminids produce mostly meteors of medium velocity.
The sigma Hydrids (HYD) are active from a radiant located at 09:03 (136) -00. This area of the sky is located in western Hydra, 3 degrees southwest of the 4th magnitude star known as theta Hydrae. With maximum activity occurring on December 17th, current rates should be near 1 per hour no matter your location. These meteors are best seen near 0300 LST, when it lies highest above the horizon in a dark sky. With an entry velocity of 58 km/sec., the average sigma Hydrid meteor would be of swift velocity.
The December Leonis Minorids (DLM) are a shower of long duration active from December 6th through January 18th. Maximum occurs near December 17th when rates may reach 3 an hour. During this period, I would expect hourly rates of 2 as seen from the northern hemisphere and 1 as seen from south of the equator. The radiant is currently located at 10:49 (162) +30. This position lies in eastern Leo Minor, 4 degrees south of the 4th magnitude star known as Praecipua (46 Leonis Minoris). These meteors are best seen near 0500 LST when the radiant lies highest above the horizon. At 63 km/sec. the December Leonis Minorids produce mostly swift meteors.
The Comae Berenicids (COM) are active from December 12-23, with maximum activity occurring on the 15th. The radiant for this source currently lies at 12:01 (180) +15. This area of the sky lies in southwestern Coma Berenices, 3 degrees east of the 2nd magnitude star known as Denebola (beta Leonis). This area of the sky is best placed near 06:00 LST, when the radiant lies highest in the sky. Current rates would less than 1 per hour no matter your location. At 65 km/sec. the Comae Berenicids produce mostly swift meteors.
The December chi Virginids (XVI) werediscovered by SonotaCo during studies of new radiants in 2008-2009. This source is active most of December with maximum occurring on December 9th. The radiant is currently located at 13:02 (195) -13, which places it in southern Virgo, 5 degrees southwest of the 1st magnitude star known as Spica (alpha Virginis). Hourly rates should be less than 1 no matter your location. These meteors are best seen during the last dark hour before dawn, when the radiant lies highest above the horizon in a dark sky. At 68 km/sec. the December chi Virginids would produce mostly swift meteors.
The December sigma Virginids (DSV) is a source of long duration discovered by John Greaves using the data of SonotaCo. This source is active from November 22 through January 25. Peak rates occur near December 21st. The current radiant location is at 13:46 (206) +05 which places it in northeastern Virgo, 4 degrees northeast of the 3rd magnitude star known as Heze (zeta Virginis A). Current hourly rates should be near 1 no matter your location. These meteors are best seen during the last dark hour before dawn, when the radiant lies highest above the horizon in a dark sky. At 66 km/sec. the December Sigma Virginids would produce mostly swift meteors.
The Ursids (URS) peak on the morning of December 22nd from a radiant located at 14:22 (215) +76. This area of the sky is located in southern Ursa Minor, near the spot occupied by the faint star known as 5 Ursae Minoris. The bright 2nd magnitude star Kochab (beta Ursae Minoris) also lies 3 degrees to the southeast of this radiant. This area of the sky is best best seen during the last hour before dawn. Rates at maximum are variable usually ranging from 5-15 as seen during the morning hours of December 22nd. At 34 km/sec. this source would produce mostly medium-slow meteors. See the article at: https://www.amsmeteors.org/2020/12/view ... r-in-2020/ for possible outbursts of the Ursids this year.
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 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. 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.
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) – 06:44 (101) +23 30 01:00 2 – 1 II
December Monocerotids (MON) Dec 13 07:10 (108) +07 41 01:00 1 – 1 II
alpha Hydrids (AHY) Jan 05 07:50 (117) -06 34 02:00 <1 – <1 IV
Geminids (GEM) Dec 14 08:02 (121) +31 34 02:00 <1 – <1 I
sigma Hydrids (HYD) Dec 17 09:03 (136) -00 58 03:00 1 – 1 II
December Leonis Minorids (DLM) Dec 17 10:49 (162) +30 63 05:00 2 – 1 II
Comae Berenicids (COM) Dec 15 12:01 (180) +15 65 05:00 <1 – <1 II
December chi Virginids (XVI) Dec 09 13:02 (195) -13 68 06:00 <1 – <1 IV
December Sigma Virginids (DSV) Dec 21 13:46 (206) +05 66 07:00 1 – 1 IV
Ursids (URS) Dec 22 14:22 (215) +76 34 08:00 <1 – <1 I
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