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суббота, 9 марта 2019 г.

Meteor Activity Outlook for March 9-15, 2019

Yes Matilda, there are fireballs in the southern hemisphere. This is a good example taken by Steve Traynor from Cherbourg, Queensland, Australia on March 18, 2018. This fireball, with a notable flare, travels among the stars of Chamaeleon and Mensa in the deep southern sky. The notable cluster in the upper right corner is the eta Carina complex. The southern celestial pole lies between the fireball and the top of the pole. © Steve Traynor

During this period the moon will reach its first quarter phase on Thursday March 14th. At this time the half-illuminated moon will be located 90 degrees east of the sun and will set near 0200 local daylight saving time (DST) as seen from mid-northern latitudes. This weekend the waxing crescent moon will set during the late evening hours and will not interfere with the more active morning hours. Hourly meteor rates for evening observers this week is near 3 as seen from mid-northern latitudes (45N) and 4 as seen from tropical southern locations (25S). For morning observers the estimated total hourly rates should be near 8 as seen from mid-northern latitudes and 11 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 slightly reduced during this period due to 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 March 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 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.

Radiant Positions at 8:00pm Local Daylight Saving Time

Radiant Positions at 1:00am Local Daylight Saving Time

Radiant Positions at 6:00am Local Daylight Saving Time

These sources of meteoric activity are expected to be active this week.

The center of the large Anthelion (ANT) radiant is currently located at 12:08 (182) -01. This position lies in western Virgo, 2 degrees west of the 4th magnitude star known as Zaniah (eta Virginis). Due to the large size of this radiant, Anthelion activity may also appear from eastern Leo, and Crater as well as Virgo. This radiant is best placed near 0200 DST, when it lies on the meridian and is located highest in the sky. Rates at this time should be near 2 per hour no matter your location. With an entry velocity of 30 km/sec., the average Anthelion meteor would be of slow velocity.

The xi Herculids (XHE) were discovered by Sirko Molau and Javor Kac of the International Meteor Organization using video data from the IMO network. These meteors are active from March 9-13 with maximum activity occurring on the 11th. The current radiant position lies near 17:12 (258) +48, which lies in northern Hercules, 5 degrees southwest of the 3rd magnitude star known as Rastaban (beta Draconis). Rates are expected to be 1 per hour as seen from the northern hemisphere and less than 1 as seen from south of the equator. These meteors are best seen during the last dark hour of the morning when the radiant lies highest above the horizon in a dark sky. At 35 km/sec. this source would produce meteors of average velocities.

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 1 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 3 per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Evening rates are slightly reduced during this period due to moonlight.

RA (RA in Deg.) DEC Km/Sec Local Daylight Saving Time North-South
Anthelion (ANT) 11:16 (169) +04 30 02:00 2 – 2 II
xi Herculids (XHE) Mar 11 17:12 (258) +48 35 07:00 1 – <1 IV

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