Meteor Activity Outlook for 16-22 December 2017

During this period the moon will reach its new phase on Monday December 18th. At that time the moon will lie near the sun and will be invisible at night. As the week progresses the waxing crescent moon will enter the evening sky but will not interfere with meteor observations. The estimated total hourly meteor rates for evening observers this week is near 5 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 23 as seen from mid-northern latitudes and 18 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 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 16/17. 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 06:32 (098) +23. This position lies in western Gemini, 3 degrees north of the 4th magnitude star known as nu 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 07:08 (107) +07. This position lies on the Monoceros/Canis Minor border, 7 degrees northwest of the brilliant zero magnitude star known as Procyon (alpha Canis Minoris). Current rates should be near 1 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 Geminids (GEM) are winding down to a small trickle from a torrent of meteors seen on the morning of December 14. This weekend the radiant is located near 07:44 (116) +32. This position lies in northern Gemini just 1 degree east of the 2nd magnitude star known as Castor (alpha Geminorum). Rates this weekend should be near 2 per hour as seen from mid-northern latitudes and 1 as seen from the southern tropics. At 34 km/sec. the Geminids produce mostly meteors of medium velocity.

The Sigma Hydrids (HYD) are active from November 26 through December 21, with maximum activity occurring on December 6 and a secondary maximum occurring on December 18. The radiant is currently located at 08:52 (133) +01 , which places it in extreme western Hydra, 3 degrees southeast of the group of 4th magnitude stars known as the “head” 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. The radiant located at 10:28 (157) +31, which lies in southern Leo Minor, 7 degrees south of the 4th magnitude star known as beta 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 December chi Virginids (XVI) was discovered by Japanese observers using the data of SonotaCo. This source is active from December 16-24 with maximum activity occurring on the 19th. The current radiant location is at 12:46 (192) -11, which places it in south-central Virgo, 10 degrees west of the bright star known as Spica (alpha Virginis). Current rates would most likely be less than 1 per hour 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 69 km/sec. the December Chi Virginids would produce mostly swift meteors.

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 13:36 (204) +04 which place it in northern Virgo some 4 degrees north of the 3rd magnitude star known as zeta Virginis. Current hourly rates would be near 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 Ursids (URS) should be active most of the week with maximum activity occurring on December 22. The radiant is currently located at 14:00 (210) +76, which places it in western Ursa Minor, just southwest of the faint star known as 5 Ursae Minoris. This area of the sky is circumpolar for most of the northern hemisphere and lies highest above the horizon in a dark sky just before dawn. Rates will be low early in the week but will peak on Friday December 22, when hourly rates should reach 5-10 per hour. At 33 km/sec. the Ursids would produce mostly medium speed meteors.

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 4 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.

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.