Dec 13/14 Geminids Recap

Last night marked the probable peak of the 2014 Geminids. Here in Tucson, we had rain during the day (0.27″) and it was looking iffy as to whether the night would remain clear of clouds and fog. I spent 1h 15m outside between 10:17 and 11:33 pm local time. Though it was very muggy and it sounded like it was still rainy as condensation dripped off the house, the night turned out to be a good one for meteor watching. I was consistently seeing 12-14 Geminids every 15 minutes so just under 1 per minute (with a limiting magnitude of ~6.1).

My camera system had an even better night as it detected 179 meteors of which 139 were Geminids over the course of the night. That is a new record for my meteor camera system having beaten the peak night of the 2010 Geminids by 20 meteors. I will try to get a video from my camera online shortly.

Geminid activity rapidly falls off after the peak. Observers may still be able to see a good number of Geminids tonight though rates will be 1/4 to 1/2 what they were last night.

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

Obs Date(UT)     Time    TOT SPO ANT GEM HYD COM Others
VIS 2014-12-14  01h 16m   71  6   -   65  -   -     -   LM=6.0-6.1
SAL 2014-12-14  12h 41m  179  21  7  139  2   2     8

SAL - SALSA3 camera in Tucson (Carl Hergenrother)
VIS - Visual observations from Tucson (Carl Hergenrother)
Time - Total amount of time each camera looked for meteors 
TOT - Total number of meteors detected
SPO - Sporadics (meteors not affiliated with any particular meteor shower)
ANT - Antihelions
GEM - Geminids
HYD - Sigma Hydrids
COM - Comae Berenicids
Others - other minor showers

Here Comes the Geminids!

Tonight is one of the best nights of the year to see a meteor as the Geminid meteor shower is predicted to reach its 2014 peak. The Geminids are one of two annual showers (the other being August’s Perseids) that are almost guaranteed to produce high rates of meteors (at least one every few minutes or better).

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

How To See Them

This year the Geminids will be near peak intensity on Saturday night/Sunday morning, December 13/14. From a dark, moon-less sky, the Geminids have consistently produced peak rates of ~100 meteors per hour. According to the IMO, the Geminids reached ZHR rates of 134 per hour in 2013, 109 in 2012, 198 in 2011, 127 in 2010, 120 in 2009, 139 in 2008, 122 in 2007 and 115 in 2006. Note, these rates assume ideal observing circumstances that are rarely achieved. Dark sky observers may see rates that approach the ZHR values. Most of us observing under light polluted skies will see lower rates (perhaps much lower for city dwellers or observers watching before 10pm).

Unlike most showers that can only be observed in the early hours of the morning, the Geminids radiant rises as early as 7 pm and a good number of meteors can be seen by 10 pm. The radiant is nearly overhead at 2 am and it still well placed for the rest of the night. This year the Last Quarter Moon (located close to a brilliant Jupiter) will hinder Geminid watching after midnight. The shower can still be observed after Moonrise though fainter meteors will be washed out. It helps to keep the Moon out of your line of sight.

As the name implies, the Geminids appear to radiate from a point in the constellation of Gemini. More specifically from a point just to the north of the bright star Castor, the northern star in the Castor-Pollux pair. During the evening Geminids will be coming out of the northeast. By the middle of the night the radiant will be close to overhead and meteors will be raining down on all sides.

In general it is best not to look directly at the radiant. Meteors are easier to see by looking 30 or more degrees from the radiant (for reference 10 degrees is the width of your hand at arms length). The key is to look up and regardless of where you look you should see quite a few Geminids.

2014_Geminids

The night sky for December 13 at 11:00pm local time over Tucson. The Geminid radiant is shown as a yellow circle with Geminid meteors radiating away from it. Chart produced with Stellarium.

.

Sky brightness matters when it comes to seeing most meteors and the Geminids are no exception. As always, the darker the sky the better. If you are located in a place with pitch black skies (mountaintops, middle of the desert, national parks) rates can be as high as ~100 per hour. In rural areas near small towns rates will be a bit lower and probably in the 80-90 per hour range. In the suburbs rates will vary depending on how close to a major city you are but you should expect rates of 20-50 per hour. In a major city rates will be very low though 2-10 per hour should be seen.

To increase your chance of seeing the Geminids find a spot with a clear view of the sky. Any obstructions (trees, buildings, etc.) can block some of the meteors. Also find a spot where lights (streetlights, security lights, etc.) aren’t shining in your eyes. This will allow your eyes to dark adapt and you will be able to see fainter, and more, meteors. The most important thing to remember is to get comfortable when observing. A lawn chair is perfect for reclining back and taking in the sky. Remember that it is cold this time of the year in the Northern Hemisphere so bundle up. It does not take much time, especially when relatively inactive, to start freezing.

Where They Come From

The Geminids were created by an enigmatic object named (3200) Phaethon. For starters Phaethon is an asteroid and only displayed what might be considered cometary activity for a few days in 2009. But meteor showers are created by comets and nearly all comets have orbits that carry them at least as far from the Sun as the orbit of Jupiter. Yet Phaethon only travels out to a distance of 2.4 AU, roughly half the distance to Jupiter’s orbit. Based on its orbit it is hard to call Phaethon anything but an asteroid.

Phaethon2014

Image of Geminid parent body (3200) Phaethon by Jean-Baptiste Kikwaya on 2014 November 27 with the Vatican Observatory VATT 1.8-m.

So what is Phaethon?

1) Phaethon could be a comet whose original orbit evolved into its current one after many millennia of close approaches with the inner planets. The probability of this happening is extremely low. Some models of the formation of the Geminids require the shower particles to be released over many centuries to millennia which is consistent with the behavior of a comet. Then again…

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 ices, 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. Or behind door #3…

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 ancient 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 from the stress of intense solar heating. 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 discrete event or events when Phaethon split or shed smaller pieces. The Daytime Sextentids and perhaps the very minor Canis Minorids were created by even older break-up events.

Though Phaethon has behaved like an asteroid since its discovery in 1983 it has been observed to ‘burp’. Near its perihelion, the asteroid is sometimes visible in near-Sun images taken with the STEREO spacecraft and occasionally appears to elongate as if it had a short tail and brighten. Analysis by David Jewitt and Jing Li (UCLA) found that Phaethon did release some surface particles. Due to intense heating (perihelion is 0.14 AU from the Sun or 7 times closer than the Earth is) some of the rocks on the surface may have fractured producing a cloud of dust which was knocked off the surface by solar radiation pressure. In effect, it is a rock comet. Still this event was very short-lived and produced a minimal amount of debris. So these type of events should not have been large enough to create the Geminids by themselves.

I penned a guest post on Phaethon for Dr. Dante Lauretta (PI of NASA’s OSIRIS-REx asteroid sample return mission) back in 2013. You can read it here.

Whether Phaeton is a traditional comet, a volatile-rich asteroid, an asteroid that split into pieces, or a ‘rock comet’, the result is going to be one of the best astronomical shows of the year. So go out and enjoy the show!

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.

gem2012overview

.

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.

world_small

x

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.

Follow

Get every new post delivered to your Inbox.

Join 106 other followers