(meteorobs) Meteor Activity Outlook for February 14-20, 2015

[Robert Lunsford]

This week sees the moon finally giving way to dark skies but the meteor activity will be slow despite the absence of moonlight. Most of the activity this week is reserved for observers in the southern hemisphere as there are 3 active radiants in the southern constellation of Centaurus. Southern sporadic rates are also near their peak while northern rates continue to dwindle.

 During this period the moon will reach its new phase on Wednesday February 18th. At this time the moon is located near the sun and is not visible at night. This weekend the waning crescent moon will rise during the mid-morning hours but will not hamper meteor viewing as long as one keeps the moon out of your field of view. The estimated total hourly meteor rates for evening observers this week is near 3 for observers situated at mid-northern latitudes and 5 for observers viewing from the southern tropics (latitude 25 S.). For morning observers the estimated total hourly rates should be near 9 for observers situated at mid-northern latitudes and 14 for observers viewing 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. 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 brightest 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 February 14/15. 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.

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

The center of the large Anthelion (ANT) radiant is currently located at 10:36 (159) +07. This position lies in southern Leo,  just south of the 4th magnitude star known Rho Leonis. Due to the large size of this radiant, Anthelion activity may also appear from Cancer, Sextans, northwestern Virgo as well as Leo. This radiant is best placed near 0100 local standard time (LST), when it lies on the meridian and is located highest in the sky. Rates at this time should be near 2 per hour as seen from the northern hemisphere and 1 per hour from south of the equator. With an entry velocity of 30 km/sec., the average Anthelion meteor would be of slow velocity.

After studies of the IMO video database provided by cameras located in Australia, Sirko Molau has determined that two more of the Centaurid radiants belonging to the southern hemisphere summer Velid-Crux-Centaurus complex may be distinguished by visual observers. These positions differ from those listed in the IAUs Meteor Data Center so actual shower members may not line up perfectly with the positions given here. The lack of cameras and actual data from the southern hemisphere prevents us from provided better parameters for these far southern radiants.  The first of these radiants, the Omega Centaurids (OCA) may be seen from February 12-16 with maximum occurring on the 14th. At maximum the radiant is predicted to be near 13:16 (199) -55. This position lies in southern Centaurus, 4 degrees southwest of the 2nd magnitude star known as Epsilon Centauri. The MDC position lies in the southern portion of the Centaurus between Pi Centauri and Gacrux (Gamma Crucis). These meteors are best seen near 0330 LST when the radiant lies highest above the horizon. Maximum rates are not known but expected to be less than 1 per hour as seen from the southern hemisphere. These meteors are not visible north of 35N latitude. They are best seen from the southern tropics where the radiant rises high into the sky and the summer nights are longer than they are at more southern locations. At 48 km/sec. the Omega Centaurids would produce meteors with average velocities.

The last of the Pi Hydrids (PIH) may be visible this weekend from a radiant located near 13:40 (205) -20. This position lies in southern Virgo, 9 degrees southeast of the 1st magnitude star known as Spica (Alpha Virginis). The closer but fainter Gamma Hydrae also lies 5 degrees southwest from the radiant. Hourly rates during this period would be less than 1 no matter your location. These meteors are best seen near 0400 LST, when the radiant lies highest above the horizon. These meteors encounter the atmosphere at 55 km/sec., which would produce meteors of swift velocity.

The 2nd of these weak Centaurid radiants are the Theta Centaurids (TCN). This radiant is also active February 12-16 with maximum occurring on the 14th. This activity may actually be detected by observers situated at mid-northern latitudes as the position lies near 13:56 (209) -29. This position lies near the Centaurus-Hydra border, 4 degrees southwest of the 3rd magnitude star known as Pi Hydrae. The MDC position lies 11 degrees further south between the stars Theta and Nu Centauri. These meteors are best seen near 0415 LST when the radiant lies highest above the horizon. Maximum rates are not known but expected to be less than 1 per hour as seen from the southern hemisphere. Although this source is visible from most of the northern hemisphere, this radiant are best seen from the southern tropics where the radiant rises higher into the sky  At 65 km/sec. most of the Theta Centaurids would produce meteors with fast velocities.

The Alpha Centaurids (ACE) were predicted to reach maximum activity on February 8th. This shower is active though February 21 so weak activity may still be seen from a radiant located at 14:32 (218) -61. This position lies in southern Centaurus between the brilliant stars Rigel Kentaurus (Alpha Centauri) and Hadar (Beta Centauri). These meteors are best seen near 0445 LST when the radiant lies highest above the horizon. Current rates would be near 1 per hour as seen from the southern hemisphere. These meteors are not visible north of 30N latitude. They are best seen from the southern tropics where the radiant rises high into the sky and the summer nights are longer than they are at more southern locations. At 56 km/sec. the Alpha Centaurids would produce mostly swift meteors.

The Beta Herculids (BHE) were discovered by Sirko Molau and Juergen Rendtel using data from the IMO database. This weak shower is best seen from February 13-16 with maximum activity occurring on the 14th. At maximum the radiant is located at 16:24 (246) +25. This position lies in southwestern Hercules, 3 degrees north of the 3rd magnitude star known as Kornephoros (Beta Herculis). These meteors are best seen during the last dark hour before dawn when the radiant lies highest above the horizon in a dark sky. Hourly rates are expected to be less than 1, even at maximum activity.  At 53 km/sec. the Beta Herculids would produce mostly swift meteors.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately 7 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 12 per hour as seen from rural observing sites and 4 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 a condensed form. Rates and positions are exact for Saturday night/Sunday morning except where noted in the shower descriptions.

Anthelion (ANT) - 10:36 (159) +07  Velocity - 30km/sec. 
Northern Hemisphere - 2 per hr.   Southern Hemisphere - 1 per hr. 
 
Omega Centaurids (OCE) - 13:16 (199) -55  Velocity - 48km/sec. 
Northern Hemisphere - <1 per hr.   Southern Hemisphere - <1 per hr

Pi Hydrids (PIH) - 13:40 (205) -20  Velocity - 55km/sec. 
Northern Hemisphere - <1 per hr.   Southern Hemisphere - <1 per hr

Theta Centaurids (TCN) - 13:56 (209) -29  Velocity - 65km/sec. 
Northern Hemisphere - <1 per hr.   Southern Hemisphere - <1 per hr 
 
Alpha Centaurids (ACE) - 14:32 (218) -61 Velocity - 56km/sec. 
Northern Hemisphere - <1 per hr.   Southern Hemisphere - 1 per hr 
 
Beta Herculids (BHE) - 16:24 (246) +25  Velocity - 53km/sec. 
Northern Hemisphere - <1 per hr.   Southern Hemisphere - <1 per hr 
 
Clear Skies! 
Robert Lunsford 	 
American Meteor Society