Meteor Activity Outlook for 9-15 December 2017

During this period the moon will reach its last quarter phase on Sunday December 10th. At that time the half-illuminated moon will lie 90 degrees west of the sun and will rise near midnight local standard time (LST) as seen from mid-northern latitudes. As the week progresses the waning moon will rise even later in the morning creating better viewing conditions. The estimated total hourly meteor rates for evening observers this week is near 4 as seen from mid-northern latitudes (45N) and 3 as seen from tropical southern locations (25S). For morning observers the estimated total hourly rates should be near 32 as seen from mid-northern latitudes and 22 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. Meteor rates are slightly reduced during the morning hours 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 December 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.

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 2017 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 Chi Orionids 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 06:00 (090) +23. This position lies on the Gemini/Taurus border, very close to the 4th magnitude star known as 1 Geminorum. Since the radiant is so large, Anthelion activity may also appear from eastern Taurus, northeastern Orion, southern Auriga as well as western Gemini. This radiant is best placed near midnight local standard time (LST) when it lies on the meridian and is highest in the sky. Rates at this time should be near 3 per hour as seen from the northern hemisphere and 2 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 Monocerotids (MON) are active from November 27th through December 27th with the peak activity occurring on December 13th. The radiant is currently located at 06:40 (100) +08. This position lies in northwestern Monoceros, 4 degrees southwest of the 3rd magnitude star known as xi Geminorum. This position is only 7 degrees south of the radiant of the November Orionids so care must be take to distinguish between the two. Current rates should be near 2 per hour no matter your location. The Monocerotids are best seen near 0100 LST when the radiant lies highest above the horizon. At 41 km/sec. the Monocerotids produce mostly meteors of medium velocity.

The November Orionids (NOO) are active from a radiant located at 06:52 (103) +15. This area of the sky is located in southern Gemini, 3 degrees southeast of the 2nd magnitude star known as Alhena (gamma Geminorum). The radiant is best placed for viewing near 0100 LST when it lies on the meridian and is highest above the horizon. Hourly rates are expected to be near 2 shower members per hour, no matter your location. With an entry velocity of 44 km/sec., the November Orionids would be of medium speed.

The Geminids (GEM) are increasing in strength with each passing night. The peak will occur on Wednesday evening/Thursday morning December 13/14. This weekend the radiant is located near 07:20 (110) +33. This position lies in northern Gemini some 3 degrees west of the 2nd magnitude star known as Castor (alpha Geminorum). Rates this weekend should be near 10 per hour as seen from mid-northern latitudes and 5 as seen from the southern tropics. At 34 km/sec. the Geminids produce mostly meteors of medium velocity. Be sure to read the article on the Geminids

The Puppid-Velids (PUP) are a vast complex of weak radiants located in the constellations of Puppis and Vela. Visual plots and photographic studies have revealed many radiants in this area during November and December. The combined strength of these radiants can produce a ZHR of ten. Actual hourly rates will be much less unless you happen to be observing from the deep Southern Hemisphere. Activity from this source begins around December 1st. The center of this activity is currently located at 08:20 (125) -45. This position lies in western Vela, 3 degrees northeast of the 2nd magnitude star known as gamma Velorum. Peak rates occur near December 7. These meteors are best seen near 0300 LST when the radiant lies highest above the horizon in a dark sky. Observers located in the Southern Hemisphere have an advantage viewing this shower as the radiant will rise higher into their sky allowing more activity to be seen. Since the radiant lies low in the south for most northern hemisphere observers, meteors seen from north of the equator tend to be long in length and long-lasting. At 40 km/sec. the Puppid-Velids produce meteors of average velocity.

The Sigma Hydrids (HYD) are active from November 26 through December 21, with maximum activity occurring on December 6. The radiant is currently located at 08:28 (127) +02 , which places it in extreme western Hydra, 2 degrees southwest of the 4th magnitude star known as sigma Hydrae. These meteors are best seen near 0400 LST when the radiant lies highest above the horizon. Hourly rates are expected to be near 3 no matter your location. With an entry velocity of 61 km/sec., most activity from this radiant would be of swift speed.

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. During this period I would expect an hourly rates near 1 from a radiant located at 10:00 (150) +34. This position lies in western Leo Minor, 1 degree southwest of the faint star known as 21 Leo Minoris. 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 Psi Ursa Majorids (PSU) were discovered by observers in Japan using data from SonotaCo. This shower is active from December 1-16 with maximum activity occurring on December 4. The radiant is currently located at 11:44 (176) +42. This position lies in southern Ursa Major, 5 degrees southeast of the third magnitude star known as Psi Ursae Majoris. This area of the sky is best placed during the last hour before dawn, when it lies highest above the horizon in a dark sky. Current rates would most likely be less than one per hour no matter your location. At 62km/sec., the average Psi Ursa Majorid meteor would be swift.

The December Sigma Virginids (DSV) was discovered by John Greaves using the data of SonotaCo. IMO video cameras confirmed that this source is active during most of December. Visual observers have their best chance at catching these meteors from December 17-31. Peak rates occur near December 24th. The current radiant location is at 13:12 (198) +07 which place it in northern Virgo some 4 degrees southeast of the 3rd magnitude star known as Vindemiatrix (epsilon Virginis). Current hourly rates would be less than 1 shower member no matter you 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 December Alpha Draconids (DAD) were discovered by the Japanese observers using data from SonotaCo and is active from November 30-Decemeber 15. They are predicted to peak on December 8th from a radiant located at 13:36 (204) +58. This position actually lies in northeastern Ursa Major, 4 degrees northeast of the second magnitude star known as Mizar (zeta Ursae Majoris). These meteors are best seen during the last dark hour before dawn, when the radiant lies highest above the horizon in a dark sky. This shower is not well seen from the southern hemisphere. Current rates would most likely be near 1 per hour as seen from the northern hemisphere. Observers south of the equator would see rates less than 1 per hour due to the lower radiant elevation.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately 12 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 4 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 8 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.

The table below presents a list of radiants that are expected to be active this week. Rates and positions are exact for Saturday night/Sunday morning except where noted in the shower descriptions.