2012 Geminids Recap

The 2012 Geminid meteor shower is now over. Dark Moon-less skies allowed for observers to get many hours of prime Geminid observing in. Here in southern Arizona the weather produced a different sort of showers on the night of the maximum as rain fell for the first time in a month. Luckily it was clear the night before maximum and rates were surprisingly strong.

The International Meteor Organization hosts a Live ZHR page that tabulated visual meteor observations from observers from all over the world and updates the shower’s activity profile in real-time. As of Dec 22, 133 observers in 36 countries reported 18,000 meteors.

Peak activity was predicted for 23:30 hours UT on December 13 making the peak effectively 0 hours UT on the 14th. From the ZHR profile below, the best rates did occur within a few hours of the predicted peak. At that time the ZHR reached ~120 meteors per hour. Even under less than perfect skies, a fine show was guaranteed.

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The IMO Live ZHR page also presents a map of the location of all 133 observers. I always find it interesting to see the distribution of meteor observers around the world. The radiant of the Geminids is located at a declination of +33° making this shower easier to see from the Northern Hemisphere. Though still visible from the latitudes of Australia, New Zealand and the middle of South America, the shower would be low on the northern horizon and rates would be much less than seen up north. Still a fair number of Southern Hemisphere observers reported meteors. It is nice to see many more observations coming in from across Asia especially in countries like Iran, India, Nepal and Thailand.

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Meteor Activity Outlook for December 15-21, 2012

The following is a slightly edited version of Bob Lunsford’s excellent weekly summary of meteor activity. The original version can be found at the American Meteor Society’s site.

No matter where you live, the first half of December provides some of the best meteor activity of the year. This activity will be tempered by a bright moon during the first week of the month. The next two weeks are moon-free and offer the meteor observer ample opportunities to view some celestial fireworks. In the northern hemisphere the sporadic rates are still strong plus you can also count on strong activity from the Geminids, which peak on December 13. There are also several minor radiants that add a few meteors each hour. All of these centers of activity are located high in the sky during the early morning hours this time of year. Much of the activity mentioned above can also be seen from the southern hemisphere. While the sporadic rates are not as strong as those seen from the north, they are stronger than the previous months and heading for a maximum in February. The warm, but short summer nights south of the equator make for some great viewing as long as the moon does not interfere.

During this period the moon reaches its first quarter phase on Wednesday December 19th. At this time the moon is located ninety degrees east of the sun and will set near midnight local standard time (LST). This weekend the waxing crescent moon will set during the early evening hours and will not cause any problems to meteor observers. As the week progresses the moon will set later and later, but will still allow unhampered views of the more active morning sky. The estimated total hourly meteor rates for evening observers this week is near four for observers located at mid-northern latitudes and three for observers in mid-southern latitudes. For morning observers the estimated total hourly rates should be near thirty from the mid-northern hemisphere and sixteen from the mid-southern hemisphere. 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. Rates are slightly reduced during the evening hours during this period due to moonlight.

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 15/16. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.

The following showers are expected to be active this week:

Now that the activity from particles produced by comet 2P/Encke has ceased encountering the Earth, the Taurid showers for 2012 are over and we resume reporting activity from the Antihelion (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 prograde 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 Antihelion. 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. 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 06:28 (097) +23. This position lies in western Gemini near the third magnitude star Mebsuta (Epsilon Geminorum). Antihelion activity may also appear from eastern Taurus, northeastern Orion, or southern Auriga. This radiant is best placed near midnight LST when it lies on the meridian and is highest in the sky. Rates at this time should be near three per hour as seen from the northern hemisphere and two per hour from south of the equator. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of slow velocity.

The December Monocerotids (MON) are active from December 7th through the 18th. Peak activity occurred on December 8th so current rates should be less than one per hour no matter your location. The radiant is located at 07:00 (105) +07. This position lies in eastern Monoceros, ten degrees east of the zero magnitude star Procyon (Alpha Canis Minoris).  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) reached maximum activity on Thursday evening/Friday morning December 13/14. This weekend will be your last good opportunity to see any Geminids in 2012 as activity ceases next week. The radiant is currently located at 07:40 (115) +32, which places it in northeastern Gemini, just east of the second magnitude star Castor (Alpha Geminorum). Rates this weekend, when the radiant lies high in the sky, would be 20-40 per hour (depending on your viewing conditions) on the night of 14/15 and 10-20 per hour on the night of 15/16. Geminid meteors strike the atmosphere at 35km/sec, which will produce meteors of medium-slow velocity.

The Sigma Hydrids (HYD) are active from November 26 through December 20. Maximum activity occurred on December 6, so current rates would be near one per hour no matter your location. The radiant is located at 08:47 (132) +01. This position lies in western Hydra, just south of the group of fourth magnitude stars that make up the “head” of the water serpent. These meteors are best seen near 0300 LST when the radiant lies highest above the horizon. At 61 km/sec. the Sigma Hydrids produce mostly swift meteors.

The December Leonis Minorids (DLM) are active from a radiant located at 10:32 (158) +32. This position lies in central Leo Minor, approximately ten degrees northeast of the third magnitude star Zeta Leonis. These meteors are best seen near 0500 LST when the radiant lies highest above the horizon. This shower peaks on December 17th so current rates would be near two per hour as seen from the northern hemisphere and less than one per hour as seen from south of the equator. At 64 km/sec. the December Leonis Minorids produce mostly swift meteors.

On the nights of December 19-21, weak activity from the Rho Leonids  (RLE) may be noticed. Sirko Molau and Juergen Rendtel of the IMO have found the actual activity range is December 17-23, but away from the nights mentioned above, the display is very weak. Previous radiants for this shower were further north. Video results give a position at maximum near 10:34 (159) -05. This actually places it in central Sextans, some fifteen degrees southeast of the first magnitude star Regulus (Alpha Leonis). Rates could approach one shower member per hour during the last few hours before dawn on the nights previously mentioned. At 69 km/sec. the Rho Leonids would produce mostly swift meteors.

On the nights of December 15/16 and 16/17, weak activity from the Virgo/Corvus border may be noticed. This currently unnamed source is active from December 5-27, but incredibly weak except for the two nights mentioned above. The exact radiant position for IMO Shower #239 is 12:52 (193) -11. This places it some ten degrees west of the first magnitude star Spica (Alpha Virginis). At 70 km/sec. These meteors are best seen during the last dark hour before dawn, when the radiant lies highest above the horizon in a dark sky. IMO Shower #239 would produce mostly swift meteors.

Another shower found by Sirko Molau and Juergen Rendtel of the IMO are the December Sigma Virginids (DSV). This radiant is active through most of December and the first week of January. Visual observers have their best chance at catching these meteors from December 17 through January 1st. Maximum activity occurs on December 31st. The current radiant location is 13:32 (203) +05, which places it in northern Virgo some five degrees north of the third magnitude star Heze (Zeta Virginis). 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 Sigma Virginids would produce mostly swift meteors.

Activity from the Ursids (URS) should begin to appear during the mid-week period from a radiant located at 13:58 (210) +76. This position lies in eastern Ursa Minor, fifteen degrees east of the second magnitude star Kochab (Beta Ursa Minoris). It must be remembered that the length of degrees are smaller in high declinations so the radiant is actually closer to this star than these figures imply. 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. Maximum activity is not expected until Saturday December 22th, so current hourly rates this week would probably be less than one. On the morning of maximum, hourly rates of between 5-10 Ursids may be seen. At 33 km/sec. the Ursids produce mostly medium-slow meteors.

Lastly, the December Alpha Draconids (DAD) are active from December 4-16. Maximum activity occurred on December 5. The radiant is currently located at 14:08 (212) +57. This position actually lies in northeastern Ursa Major, ten degrees northeast of the second magnitude double star 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. Expected hourly rates would be less than one no matter your location. At 44 km/sec. the Alpha Draconids produce mostly medium speed meteors.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately eleven sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near three per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near seven per hour as seen from rural observing sites and two per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Evening rates are slightly reduced due to moonlight.

The list below presents a condensed version of the expected activity this week.
Rates and positions are exact for Saturday night/Sunday morning.

Antihelions (ANT) – 06:28 (097) +23   Velocity – 30km/sec.
Northern Hemisphere – 3 per hr.   Southern Hemisphere – 2 per hr

Dec. Monocerotids (MON) – 07:00 (105) +07   Velocity – 41km/sec.
Northern Hemisphere – <1 per hr.   Southern Hemisphere – <1 per hr

Geminids (GEM) -07:40 (115) +32   Velocity – 35km/sec.
Northern Hemisphere – 10 per hr.   Southern Hemisphere – 5 per hr

Sigma Hydrids (HYD) -08:47 (132) +01   Velocity – 61km/sec.
Northern Hemisphere – 1 per hr.   Southern Hemisphere – 1 per hr

December Leonis Minorids (DLM) – 10:32 (158) +32   Velocity – 64km/sec.
Northern Hemisphere – 2 per hr.  Southern Hemisphere – <1 per hr

Rho Leonids (RLE) – 10:34 (159) -05   Velocity – 69km/sec.
Northern Hemisphere – 1 per hr.  Southern Hemisphere – 1 per hr

IMO #239  – 12:52  (193) -11   Velocity – 69km/sec.
Northern Hemisphere – 2 per hr. Southern Hemisphere – <1 per hr

Dec. Sigma Virginids (DSV) – 13:32 (203) +05   Velocity – 44km/sec.
Northern Hemisphere – <1 per hr. Southern Hemisphere – <1 per hr

Ursids (URS)  – 13:58 (210) +76    Velocity – 33km/sec.
Northern Hemisphere – <1 per hr. Southern Hemisphere – <1 per hr

December Alpha Draconids (DAD) – 14:08 (212) +57   Velocity – 44km/sec.
Northern Hemisphere – <1 per hr. Southern Hemisphere – <1 per hr

Clear Skies!
Robert Lunsford
American Meteor Society

Geminids Peak

The Geminids meteor shower was forecast to reach its peak last night (Dec. 13/14, Thu/Fri night). According to reports submitted to the International Meteor Organization, Zenithal Hourly Rates (ZHR) may have reached as high as 140-150 per hour around midnight last night Tucson time. This high peak seems to have been rather sharp and other observers recorded ZHRs in the 60-100 range.

ZHR rates for the 2012 Geminids from the IMO's Live ZHR page. Credit: International Meteor Organization.

ZHR rates for the 2012 Geminids from the IMO’s Live ZHR page. Credit: International Meteor Organization.

Here in Tucson we had a different kind of shower as it rained for the first time in a month. With ~0.58″ of rain last night it was the wettest event since late August. Luckily it does appear that Geminid rates on Wed/Thu night were almost, if not, as good as rates during the peak night. The Geminid rates routinely fall off rapidly after the peak so though some Geminids should be visible tonight rates may be much lower than the past two nights.

Salvador Aguirre operates an allsky fireball camera in Hermosilla, Sonora. The youtube video below is his compilation of meteors from Wed/Thu night. More can be seen on his blog.

Great Geminids Display Last Night

The Geminids aren’t expected to peak till tonight and yet last night they were definitely alive and kicking. In fact, I would rank last night’s display as one of the better (non-Leonid outburst) showers that I have ever seen. Makes me wonder if tonight will be even better or are the Geminids peaking early.

Tonight it is supposed to rain here in Tucson so I decided to make last night my dedicated Geminid watch night. Within about 2-3 minutes of stepping outside I had already seen 4 Geminids. Things were looking good. Between 8:08 and 10:26 UT (1:08 and 3:26 am local time) I counted 154 Geminids and 24 sporadics (really non-Geminids since I wasn’t keeping track of any of the other active showers) under a sky with a limiting magnitude of +6.1. The Geminids came in bunches. There were multiple occurrences of 3-4 Geminids visible within a span of 10-30 seconds. At the other extreme there were a few dry spells when no meteors were seen for about 4 minutes. The brightness of the Geminids also seemed to be patchy with 10-20 minutes of bright 0th to 2nd magnitude meteors followed by 10-20 minutes of only 3rd magnitude or fainter ones.

The best meteor of the night was not a Geminid but a nice -4 magnitude sporadic that flared a few times right in the middle of my view. Its motion was consistent with being a Sigma Hydrid, one of the lesser showers active last night.

The IMO’s Live ZHR graph showed the Geminids reaching a ZHR rate of ~110 meteor per hour last night.

The weather is expected to be bad for Tucson tonight so I doubt I’ll be able to watch. But for those of you under clear skies, the Geminids will surely put on a nice show. The best time to watch is between 10 pm and dawn. Though the meteors appear to radiate from the constellation of Gemini (from the northeast between 10 pm and midnight, overhead between midnight and 4am and from the northwest from 4am till dawn) the meteors can be seen anywhere in the sky. Where you look isn’t as important as finding a comfortable position (reclining chairs are the best) with an unobstructed view free from lights, buildings and trees. Also remember it is cold out there and meteor watching involves lots of sitting still so dress even warmer than you would otherwise.

Happy viewing!

See the Geminids this Week

The next few nights bring the peak the Geminids, one of the year’s better meteor showers. It’s usually a toss up as to which is better, the Perseids of August or the Geminids, though lately the Geminids have been routinely out-producing the Perseids. If the sky is clear it will provide one of the few nights of the year when it’s almost guaranteed that you will be able to observe a meteor after about 10-20 minutes of observing.

From a dark, moon-less sky, the Geminids have been known to consistently produce rates of over 100 meteors per hour at their peak. Unlike most showers that can only be observed in the early hours of the morning, the Geminids can be seen in good numbers as early as 10 pm and are great anytime after midnight. The Geminids will appear to radiate from the constellation of Gemini near the bright star Castor.

For observers in the US the best time should be Thursday/Friday night. Still a good display should be visible tonight (Wed/Thu night) as well. Last night (Tue/Wed night) rates reached a ZHR of ~30-40 per hour. Tonight rates should be even better, probably in the range of 40-60. Note that ZHR rates of 40-60 will only be visible to observers under very dark skies with the radiant overhead. Most of us will see lower rates due to light pollution. The brighter your sky the less meteors you’ll see.

For more information on observing the Geminids, check out Bob Lunsford’s post at the American Meteor Society.

The International Meteor Organization has a live real-time display of Geminid rates.

For more on Phaethon, the source asteroid of the Geminids, check out this NASA Science News report.

December 11 Meteors

Possible meteor activity from the 1947 dust trail of periodic comet 46P/Wirtanen was predicted for last night. I decided to go out and watch for an hour centered on the time of the expected peak (06:21 UT). Unfortunately no ‘Wirtanen-ids’ were seen. I did catch 8 Geminids and 5 sporadic (those not affiliated with any meteor shower, or at least none that I was monitoring) meteors. The highlight of the night was three meteors (1 Geminid and 2 sporadics) seen in rapid succession all within a span of 20 or so seconds.

So far there have been no reports of any ‘Wirtanen-id’. Bob Lunsford was also observing at nearly the same time as I was except he was observing in southern CA and he also did not see any activity.

It will be interesting to see if any activity is seen during the three remaining dust trail crossings: the 1941 trail at 10:20 UT on Dec. 12, the 1934 trail at 12:30 UT on Dec. 13 and the 1927 trail at 00:02 UT on Dec. 14. The Dec 12 and 13 crossings will not be visible from the United States while the Dec 14 crossing will be visible from the eastern US. Of course, our understanding of meteor trails and even the motion of 46P prior to its discovery in 1948 is not exact so it is possible that trail crossings might happen at other times, if at all.

Meteor Activity Outlook for December 8-14, 2012

The following is a slightly edited version of Bob Lunsford’s excellent weekly summary of meteor activity. The original version can be found at the American Meteor Society’s site.

No matter where you live, the first half of December provides some of the best meteor activity of the year. This activity will be tempered by a bright moon during the first week of the month. The next two weeks are moon-free and offer the meteor observer ample opportunities to view some celestial fireworks. In the northern hemisphere the sporadic rates are still strong plus you can also count on strong activity from the Geminids, which peak on December 13. There are also several minor radiants that add a few meteors each hour. All of these centers of activity are located high in the sky during the early morning hours this time of year. Much of the activity mentioned above can also be seen from the southern hemisphere. While the sporadic rates are not as strong as those seen from the north, they are stronger than the previous months and heading for a maximum in February. The warm, but short summer nights south of the equator make for some great viewing as long as the moon does not interfere.

During this period the moon reaches its new phase on Thursday December 13th. At this time the moon is located near the sun and will be invisible at night. This weekend the waning crescent moon will rise during the early morning hours. It will be a minor inconvenience that can be overcome by simply viewing with the moon at your back.  The estimated total hourly meteor rates for evening observers this week is near four for observers located at mid-northern latitudes and three for observers in mid-southern latitudes. For morning observers the estimated total hourly rates should be near twenty from the mid-northern hemisphere and sixteen from the mid-southern hemisphere. 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. Rates are slightly reduced during the morning hours during this period due to moonlight.

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 8/9. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.

The following showers are expected to be active this week:

Meteors from comet 46P\Wirtanen? There is the possibility that we may be able to see meteor activity from comet 46P\Wirtanen as the Earth passes through several filaments of material produced when the comet passed through perihelion during the first half of the 20th century. This is strictly an evening display as any meteors from this source would have a radiant of 23:48 (357) +04. This position lies in western Pisces, just east of the circle of faint stars known as the “Circlet”. This area of the sky is best seen as it becomes dark as it culminates between 1800 and 1900 (6pm and 7pm) local standard time. The first of these encounters is with the material shed in 1947. The expected peak is at 06:21 Universal Time (UT) on December 11th. This corresponds to 22:21 (10:21pm) PST and 23:21 (11:21pm) MST on Monday evening December 10th. The radiant is too low for any activity to be seen in the eastern half of North America. The second encounter is material from 1941. This peak is expected to occur at 10:20 UT on December 12th. This is too late for North America but observers in Hawaii may be able to see some of this activity. The third encounter is produced from the 1934 return. This peak is expected to occur at 12:30 UT on December 13th. This timing favors the western Pacific area. The last possible encounter is produced by the 1927 return. This peak is expected to occur at 00:02 UT on December 14th. This corresponds to 19:02 (7:02pm) EST and 18:02 (6:02pm) CST on the evening of December 13th. This timing favors the eastern half of North America. If any meteors are produced from this source, they would be extremely slow.

The last of the Northern Taurids (NTA) can be seen this weekend from a radiant centered at 05:26 (082) +27. This area of the sky lies in northeastern Taurus, two degrees south of the second magnitude star El Nath (Beta Tauri). The radiant is best placed near 0100 LST, when it lies highest above the horizon. Maximum activity occurred on November 13th so current hourly rates would be near one from the northern hemisphere and less than one from south of the equator. Meteors from the Northern Taurids strike the atmosphere at 29km/sec., which would produce meteors of slow velocity.

The Monocerotids (MON) are active from December 7th through the 18th. Peak activity occurs on December 8th with the radiant is located at 06:36 (099) +08. This position lies in northern Monoceros, eight degrees east of the first magnitude orange star Betelgeuse (Alpha Orionis). Current rates should be near one 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) reach maximum activity on Thursday evening/Friday morning December 13/14, when approximately 75 shower members can be seen each hour from rural observing sites. While the Geminids are currently the most active radiant in the sky, rates this weekend will only be near five shower members per hour. Rates will increase dramatically as we approach the maximum date and the moon wanes. The radiant is currently located at 07:14 (109) +33. This position lies in northern Gemini, four degrees west of the second magnitude star Castor (Alpha Geminorum).  Although Geminid meteors can be seen all night long, they are best seen near 0200 LST when the radiant lies highest above the horizon. Geminid activity can be seen from the southern hemisphere but at much reduced rate. As seen from south of the equator, Geminid activity could only be seen for a few hours before and after 0200 LST. At 35 km/sec. the Geminids produce mostly meteors of medium velocity. This is one of the few displays that can be well seen prior to midnight. Geminid meteors seen just after dusk will be very long with a long duration. This is due to the fact that the radiant will lie near the horizon and any Geminid meteor seen be just be skimming the upper regions of the atmosphere. Therefore they will take longer to disintegrate in the much less dense portion of the atmosphere. Geminid meteors strike the atmosphere at 35km/sec, which will produce meteors of medium-slow velocity.

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 zenith hourly rate (ZHR) of ten at maximum, which occurs near December 7. Actual hourly rates will be much less unless you happen to be observing from the deep Southern Hemisphere. The center of this activity is currently located at 08:08 (124) -45. This position lies in western Vela, three degrees northeast of the second magnitude star Gamma Velorum. 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. At 40 km/sec. the Puppid-Velids produce meteors of average velocity.

The Sigma Hydrids (HYD) are active from November 26 through December 20. Maximum activity occurred on December 6 and this radiant is currently the third most active in the sky. The radiant is located at 08:24 (126) +02. This position lies in western Hydra, just west of the group of fourth magnitude stars that make up the “head” of the water serpent. These meteors are best seen near 0300 LST when the radiant lies highest above the horizon. Current rates would be near three per hour no matter your location. At 61 km/sec. the Sigma Hydrids produce mostly swift meteors.

The December Leonis Minorids (DLM) are active from a radiant located at 10:08 (152) +36. This position lies in central Leo Minor, approximately twelve degrees north of the third magnitude star Zeta Leonis. These meteors are best seen near 0500 LST when the radiant lies highest above the horizon. This shower peaks on December 17th so current rates would be near one per hour as seen from the northern hemisphere and less than one per hour as seen from south of the equator. At 64 km/sec. the December Leonis Minorids produce mostly swift meteors.

Lastly, the December Alpha Draconids (DAD) are active from December 4-16. Maximum activity occurred on December 5. The radiant is currently located at 13:40 (205) +60. This position actually lies in northeastern Ursa Major, direct between the fourth magnitude star Thuban (Alpha Draconis) and the second magnitude double star 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. Expected hourly rates would be less than one no matter your location. At 44 km/sec. the Alpha Draconids produce mostly medium speed meteors.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately seven sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near three per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near four per hour as seen from rural observing sites and two per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Morning rates are reduced due to moonlight.

The list below presents a condensed version of the expected activity this week.
Rates and positions are exact for Saturday night/Sunday morning.

Northern Taurids (NTA) -  05:26 (082) +27   Velocity – 29km/sec.
Northern Hemisphere – 1 per hr.   Southern Hemisphere – <1 per hr

Dec. Monocerotids (MON) – 06:36 (099) +08   Velocity – 41km/sec.
Northern Hemisphere – 1 per hr. Southern Hemisphere – 1 per hr

Geminids (GEM) – 07:14 (109) +33   Velocity – 35km/sec.
Northern Hemisphere – 5 per hr.   Southern Hemisphere – 3 per hr

Puppid-Velids (PUP) – 08:08 (124) -45   Velocity – 40km/sec.
Northern Hemisphere – 1 per hr. Southern Hemisphere – 5 per hr

Sigma Hydrids (HYD) – 08:24 (126) +02   Velocity – 61km/sec.
Northern Hemisphere – 3 per hr.   Southern Hemisphere – 3 per hr

December Leonis Minorids (DLM) – 10:08 (152) +36   Velocity – 64km/sec.
Northern Hemisphere – 1 per hr. Southern Hemisphere – <1 per hr

December Alpha Draconids (DAD) – 13:40 (205) +60   Velocity – 44km/sec.
Northern Hemisphere – 1 per hr. Southern Hemisphere – <1 per hr

Clear Skies!
Robert Lunsford
American Meteor Society

In the Transient Sky – December 2012

December 2012 Highlights
* Geminid meteor shower peaks on the night of December 14/15
* Jupiter bright in the eastern evening sky
* Jupiter and the Moon make a spectacular Christmas pair
* Comet C/2012 K5 (LINEAR) brightens to 8th magnitude

Note: If anyone has pictures or observations of these objects/events and want to share them with my readers, send them to the Transient Sky at <transientsky1@yahoo.com>.

Planets

Evening Planets

Mars - One needs a very clear southeast horizon to catch Mars in the early evening. Glowing at magnitude +1.2 Mars is currently not as bright as other planets. But it is traveling through a patch of sky with few bright stars so it is rather apparent as the brightest, reddest, “star” in that part of the sky. It spends most of the month against the stars of eastern Sagittarius before approaching Capricornus at the end of the month. The Moon passes near Mars on the evening of the 14th.

Jupiter – Jupiter reaches opposition on December 2nd. At that time it is at its brightest (magnitude -2.7) and closest to Earth (4.07 AU). It spends the month slowly retrograding just north of the stars of the Hyades cluster in Taurus. At the start of the month it rises in the northeast at sundown. By the end of the month, it is well up in the eastern sky by nightfall. On Christmas night, the Moon and Jupiter will make a beautiful pair.

Morning Planets

Saturn – Saturn is an early morning object rising around 4:30-5:00 am at the start of the month. By the end of the month, Saturn rises 2 hours earlier.  All month Saturn glows at magnitude +1.3. The Moon passes close to Saturn on the mornings of the 10th.

Venus – Venus rises around 5:00 am on the 1st and 6:00 am on the 31st. In a telescope the planet will appear more than half-illuminated (about 90%). At magnitude -3.8, Venus is by far the brightest ‘star’ in the morning sky.  The Moon passes to the south of Venus on the morning of the 11th. Venus will become more and more difficult to observe over the coming months as it approaches conjunction with the Sun.

Mercury – Mercury is the last of the morning planets to rise. On the 1st it is magnitude -0.2 and rises around 5:30 – 6:00 am. It is still observable peaking above the southeast horizon just before day break through the middle of the month.

Meteors

The year is usually split in 2 with January through June having low rates with few major showers while July through December have high rates with many major showers. Meteor activity is still near an annual maximum this month.

Sporadic Meteors

Sporadic meteors are not part of any known meteor shower. They represent the background flux of meteors. Except for the few days per year when a major shower is active, most meteors that are observed are Sporadics. This is especially true for meteors observed during the evening. During December mornings, 10 or so Sporadic meteors can be observed per hour from a dark moonless sky.

Major Meteor Showers

Geminids (GEM) [Max Date = Dec. 13, Max ZHR = ~120 per hour]

The night of December 13/14 will bring the peak the Geminids, one of the year’s better meteor showers. It’s usually a toss up as to which is better, the Perseids of August or the Geminids, though lately the Geminids have been routinely out-producing the Perseids. If the sky is clear it will provide one of the few nights of the year when it’s almost guaranteed that you will be able to observe a meteor after about 10-20 minutes of observing.

From a dark, moon-less sky, the Geminids have been known to consistently produce rates of over 100 meteors per hour at their peak. Unlike most showers that can only be observed in the early hours of the morning, the Geminids can be seen in good numbers as early as 10 pm and are great anytime after midnight. The Geminids will appear to radiate from the constellation of Gemini near the bright star Castor.

According to analysis of meteor video data by Sirko Molau, the Geminids are active for almost an entire month between the dates of November 23 and December 21. Though high rates are only possible within a few days of the peak.

The International Meteor Organization (IMO) has a “live” graph showing the rate of the Geminids as reported by visual observers around the world.

Most meteor showers are produced by comets with orbits that extend out to the orbit of Jupiter or beyond. The Geminids are different. They are on a very short uncomet-like orbit that extends from a very close 0.14 AU from the Sun to a not so far 2.40 AU.

1) Phaethon could be a comet whose original orbit evolved into its current one after many millennia of close approaches with the inner planets. Some models of the formation of the Geminids require the shower particles to be released over many centuries to millennia. This is consistent with the behavior of a comet.

2) Phaethon may be a Main-Belt comet. Main-Belt comets are objects that originate in the outer Asteroid, or Main, Belt. Since they contain a sizable fraction of volatile material (water, carbon monoxide, etc.), they can occasionally exhibit cometary activity. Four of these objects have been observed to display cometary activity in the Main Belt. Since they start on asteroid orbits, it is not too difficult for one of them to find itself on an orbit similar to Phaethon.

3) Phaethon is an asteroid that broke up in the past. There is evidence to suggest that Phaethon is just the largest piece of a past break-up. In fact, two additional asteroids that may once have been a part of Phaethon have been found, (155140) 2005 UD and 1999 YC. According to Peter Jennisken’s book “Meteor Showers and Their Parent Comets”, the Geminids can be explained by the break-up of Phaethon just after perihelion many orbits ago. Since Phaethon gets to within 0.14 AU (14% of the Earth-Sun distance), perhaps it split under the intense solar heat. BTW, this scenario does not rule out Phaethon as a ice-rich Main-Belt comet.

The recent discovery of additional asteroids related to Phaethon points to scenario 3 as the most likely origin of the Geminids. If true, the Geminids were not the result of long-term cometary activity like most meteor showers but were created in a single event when Phaethon split or shed a smaller piece. The Daytime Sextentids and perhaps the very minor Canis Minorids were created by even older break-up events.

The video below contains 159 meteors detected by my SALSA3 camera during the 2010 Geminids peak over Tucson. It starts in the evening where you can catch a short glimpse of the Moon as it quickly moves out of the frame. Note the top of one of my trees illuminated by Christmas lights for the first few meteors. Though not all of the meteors are Geminids most are and it is fun to watch them radiate from the twin stars of Castor and Pollux.

GEMS

Minor Meteor Showers

Minor showers produce so few meteors that they are hard to notice above the background of regular meteors. Info on many minor showers are provided on a weekly basis by Robert Lunsford’s Meteor Activity Outlook.

Additional information on these showers and other minor showers not included here can be found at the International Meteor Organization’s 2012 Meteor Shower Calendar.

Comets

Naked Eye Comets (V < 6.0)

None this month.

Binocular Comets (V = 6.0 – 8.0)

None this month

Small Telescope Comets (V = 8.0 – 10.0)

C/2012 K5 (LINEAR)

This is a long-period comet discovered by the LINEAR near-Earth asteroid survey program on May 25, 2012. At the time the comet was around magnitude 17-18. Though it passed through perihelion on Nov. 28 at a distance of 1.14 AU, the comet will become brighter this month as it rapidly approaches the Earth. Close approach will occur at the very end of December at a distance of 0.29 AU (27 million miles or 44 million km).

Recent visual observations place the comet around magnitude 10.0 at the end of November. The comet should brighten by another 2 magnitudes by the end of December. This month it is primarily a northern hemisphere object and spends much of the month running the length of the Big Dipper from the handle to the bowl before rocketing southward through the rest of Ursa Major into Lynx. The fact that it spends the first 3 weeks of the month among the familiar stars of the Big Dipper should aid many people in seeing the comet.

The comet starts the month as a small telescope object but by the middle of the month it should be visible in binoculars for observers under a dark sky. For bright sky observers a small telescope may still be needed.

I did observe the comet back on Oct. 21 with the University of Arizona’s Kuiper 1.5-m telescope. Though still over a month from perihelion and located low in the sky, the comet displayed an impressive tail and even some near-nucleus jet activity.

C2012K5_2012Nov21

Ephemeris for C/2012 K5 (LINEAR)
Date            RA        DEC    Delta   r   Elong    V
2012 Dec 01   14h 03m  +45d 41'  0.881 1.142   75    9.9
2012 Dec 11   13h 33m  +50d 48'  0.643 1.158   88    9.3
2012 Dec 21   11h 53m  +60d 05'  0.418 1.196  110    8.7
2012 Dec 31   06h 48m  +49d 48'  0.294 1.253  153    8.0

RA = Right Ascension, DEC = Declination, Delta = distance from Earth in AU
r = distance from the Sun in AU, Elong = elongation from Sun in degrees
V = Visual magnitude

Meteor Activity Outlook for December 1-7, 2012

The following is a slightly edited version of Bob Lunsford’s excellent weekly summary of meteor activity. The original version can be found at the American Meteor Society’s site.

No matter where you live, the first half of December provides some of the best meteor activity of the year. This activity will be tempered by a bright moon during the first week of the month. The next two weeks are moon-free and offer the meteor observer ample opportunities to view some celestial fireworks. In the northern hemisphere the sporadic rates are still strong plus you can also count on strong activity from the Geminids, which peak on December 13. There are also several minor radiants that add a few meteors each hour. All of these centers of activity are located high in the sky during the early morning hours this time of year. Much of the activity mentioned above can also be seen from the southern hemisphere. While the sporadic rates are not as strong as those seen from the north, they are stronger than the previous months and heading for a maximum in February. The warm, but short summer nights south of the equator make for some great viewing as long as the moon does not interfere.

During this period the moon reaches its last quarter phase on Thursday December 6th. At this time the moon is located ninety degrees west of the sun and rises near 2300 (11pm) local standard time (LST). This weekend the waning gibbous moon will rise during the early evening hours and will effectively spoil the sky the remainder of the night with its intense lunar glare. The estimated total hourly meteor rates for evening observers this week is near four for observers located at mid-northern latitudes and three for observers in mid-southern latitudes. For morning observers the estimated total hourly rates should be near twelve from the mid-northern hemisphere and seven from the mid-southern hemisphere. 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. Rates are reduced during this period due to moonlight.

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 1/2. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.

Details of each active shower will return next week when the observing conditions improve.

The following radiants are expected to be active this week.  Rates and positions are exact for Saturday night/Sunday morning .

Dec. Phoenicids (PHO) – 01:00 (015) -53    Velocity – 18km/sec.
Northern Hemisphere – <1 per hr.    Southern Hemisphere – <1 per hr.

Andromedids (AND) – 01:28 (022) +55   Velocity – 19km/sec.
Northern Hemisphere – <1 per hr.   Southern Hemisphere – <1 per hr.

Northern Taurids (NTA) – 05:03 (076) +26   Velocity – 29km/sec.
Northern Hemisphere – 1 per hr.   Southern Hemisphere – <1 per hr.

November Orionids (NOO) – 06:10 (093) +15   Velocity – 44km/sec.
Northern Hemisphere – 2 per hr.   Southern Hemisphere – 1 per hr.

Geminids (GEM) – 06:47 (102) +34   Velocity – 35km/sec.
Northern Hemisphere – 1 per hr.   Southern Hemisphere – <1 per hr.

Puppid-Velids (PUP) – 08:00 (120) -45   Velocity – 40km/sec.
Northern Hemisphere – <1 per hr. Southern Hemisphere – 1 per hr.

Sigma Hydrids (HYD)  – 08:04 (121) +04   Velocity – 61km/sec.
Northern Hemisphere – 1 per hr. Southern Hemisphere – 1 per hr.

Dec. Kappa Draconids (DKD) – 12:17 (184) +71   Velocity – 43km/sec.
Northern Hemisphere -<1 per hr. Southern Hemisphere – <1 per hr.

Clear Skies!
Robert Lunsford
American Meteor Society

Meteor Activity Outlook for December 3-9, 2011

The following is a slightly edited version of Bob Lunsford’s excellent weekly summary of meteor activity. The original version can be found at the American Meteor Society’s site.

No matter where you live, the first half of December provides some of the best meteor activity of the year. Unfortunately in 2011, the moon will spoil much of this activity as I reaches its full phase on the 10th. In the northern hemisphere the sporadic rates are still strong plus you can also count on strong activity from the Geminids, which peak on December 14. There are also several minor radiants that add a few meteors each hour. All of these centers of activity are located high in the sky during the early morning hours this time of year. Much of the activity mentioned above can also be seen from the southern hemisphere. While the sporadic rates are not as strong as those seen from the north, they are stronger than the previous months and heading for a maximum in February. The warm, but short summer nights south of the equator make for some great viewing as long as the moon does not interfere.

During this period the moon waxes from half illuminated to nearly full by the end of the period. This weekend the waxing gibbous moon will set during the early morning hours, allowing a few hours of observing under dark skies between moon set and the start of morning twilight. The estimated total hourly rates for evening observers this week is near three as seen from the northern hemisphere and two as seen from the southern hemisphere. For morning observers the estimated total hourly rates should be near twenty two as seen from mid-northern latitudes and eighteen from mid-southern latitudes. 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 reduced due to moonlight.

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 3/4. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.

The following showers are expected to be active this week:

The December Phoenicids (PHO) are a periodic shower that rarely produces noticeable activity. The only impressive display produced by this shower occurred in 1956 when ZHR’s were near 100. Peak activity occurs on December 6. Little activity is expected away from the peak night. The radiant is currently located at 00:46 (016) -53. This position lies in eastern Phoenix, five degrees northwest of the first magnitude star Archernar (Alpha Eridani). These meteors are best seen near 2000 (8pm) local standard time (LST), when the radiant lies highest above the horizon in a dark sky. Due to the southerly declination of the radiant, this shower is not visible north of the northern tropical areas. The deep southern hemisphere has the best chance of seeing any activity. At 22 km/sec. the Phoenicids produce very slow meteors.

The last of the Northern Taurids (NTA) for 2011 will be seen this week from a large radiant centered at 05:09 (077) +26. This position lies in eastern Taurus, five degrees southwest of the second magnitude star El Nath (Beta Tauri). The radiant is best placed near midnight LST, when it lies highest above the horizon. Since the radiant is large, Northern Taurid meteors may also appear to come from southern Auriga, southeastern Perseus, northern Orion, and western Gemini as well as Taurus. Meteors from the Northern Taurids strike the atmosphere at 29km/sec., which would produce meteors of slow velocity. Expected rates would be near two per hour, no matter your location.

The November Orionids (NOO) were recently discovered by Sirko Molau and Jueregen Rendtel by analyzing video data from the IMO network. For years this radiant was lost in the maze of radiants active this time of year. Due to the low activity, visual observers were unable to detect this shower. This shower is active from November 18 through December 9. Maximum activity occurred on November 30. Once you know the radiant in advance, this shower is actually quite noticeable, producing an average of two shower members per hour near maximum. The radiant is currently located at 06:16 (094) +15. This position lies in northeastern Orion, seven degrees northeast of the orange first magnitude star Betelgeuse (Alpha Orionis). These meteors are best seen near 0100 LST when the radiant lies on the meridian and highest above the horizon. At 44 km/sec. the November Orionids produce mostly medium velocity meteors.

The Monocerotids (MON) are active from December 7th through the 18th. Peak activity occurs on December 8th. On the night of maximum activity the radiant is located at 06:37 (099) +08. This position lies in northern Monoceros, eight degrees south of the second magnitude star Alhena (Gamma Geminorum). Rates at maximum should be near one 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.

Geminid (GEM) activity begins this weekend from a radiant located at 06:55 (104) +34. This position lies in northern Gemini, near the fourth magnitude star Theta Geminorum. Expected rates this weekend would only be near one per hour as maximum is still ten days away. Although Geminid meteors can be seen all night long, they are best seen near 0200 LST when the radiant lies highest above the horizon. This shower peaks on the night of December 14, when rates can surpass 60 shower members per hour in moonless skies. Unfortunately this year there will be a bright moon and observers will be limited to seeing no more than 20-30 meteors per hour. Geminid activity can be seen from the southern hemisphere but at much reduced rate. As seen from south of the equator, Geminid activity could only be seen for a few hours before and after 0200 LST. At 35 km/sec. the Geminids produce mostly meteors of medium velocity.

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 08:05 (121) -45. This position lies in western Vela, two degrees north of the second magnitude star 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 20. Maximum activity occurs on December 6 from a radiant located at 08:11 (122) +03. This position lies on the Hydra/Canis Minor border, seven degrees southeast of the brilliant zero magnitude star Procyon (Alpha Canis Minoris). These meteors are best seen near 0300 LST when the radiant lies highest above the horizon. Current rates would be near two per hour no matter your location. At 61 km/sec. the Sigma Hydrids produce mostly swift meteors.

Activity from the December Leonis Minorids (DLM) begin next week from a radiant located at 09:56 (149) +37. This position lies in central Leo Minor, seven degrees northeast of the fourth magnitude star Alpha Lyncis. These meteors are best seen near 0500 LST when the radiant lies highest above the horizon. This shower peaks on December 20th so current rates would be near one per hour as seen from the northern hemisphere and less than one per hour as seen from south of the equator. At 64 km/sec. the December Leonis Minorids produce mostly swift meteors.

Another shower verified by video means are the Psi Ursa Majorids (PSU). This shower is active from November 29-December 13 with maximum activity occurring on December 5. On Tuesday the radiant is located at 11:07 (167) +43. This position lies in southern Ursa Major, one degree south of the third magnitude star 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. At 61km/sec., the average Psi Ursa Majorid meteor would be swift.

Another shower verified by video means are the December Kappa Draconids (KDR). This shower is active from November 30-December 6 with maximum activity occurring on December 3rd. On the night of maximum the radiant will be located at 12:24 (186) +70. This position lies in extreme western Draco, close to the faint star Kappa Draconis. While the radiant lies above the horizon all night for most of the northern hemisphere, it 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. At 43km/sec., the average December Kappa Draconid meteor would be of medium velocity.

Lastly, the December Alpha Draconids (DAD) are active beginning Sunday from a radiant located at 13:31 (203) +60. This position actually lies in northeastern Ursa Major, five degrees north of the second magnitude double star 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. Maximum activity is expected on Monday December 5th, but hourly rates would probably be less than one no matter your location. At 44 km/sec. the Alpha Draconids produce mostly medium speed meteors.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately twelve sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near two per hour. As seen from the mid-southern hemisphere (45S), morning rates would be near six per hour as seen from rural observing sites and one per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Evening rates are reduced due to moonlight.

The list below presents a condensed version of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning.

Shower Name                 RA     DEC   Vel     Rates
                                         km/s   NH    SH
PHO Dec Phoenicids        00h 46m  -52    18    <1    <1
NTA Northern Taurids      05h 09m  +26    29     2     2
NOO November Orionids     06h 16m  +15    44     2     2
MON Monocerotids          06h 37m  +08    41     1     1
GEM Geminids              06h 55m  +34    35     1     1
PUP Puppids-Velids        08h 05m  -45    40    <1     2
HYD Sigma Hydrids         08h 11m  +03    61     2     2
DLM Dec Leonis Minorids   09h 56m  +37    64     1    <1
PSU Psi Ursa Majorids     11h 07m  +43    61    <1    <1
KDR Dec Kappa Draconids   12h 24m  +70    43    <1    <1
DAD Dec Alpha Draconids   13h 31m  +60    44    <1    <1

RA - Right Ascension
DEC - Declination
Vel - Velocity relative to Earth (in km per sec)
Rates - Rate of visible meteors per hour from a dark site
NH - Northern Hemisphere
SH - Southern Hemisphere
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