Geminids 2011

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Alastair McBeath
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Geminids 2011

Post by Alastair McBeath »

Rounding-off a generally poor last quarter for major meteor showers (aside from the UK's weather entirely failing to cooperate in helping us see anything of them!), the Geminids have a problematic waning gibbous Moon not far southeast of the radiant for their maximum on December 14. However, near-peak Zenithal Hourly Rates (ZHRs) up to 120 or so are expected between roughly 01h-22h UT then, so UK watchers could still enjoy something of the brighter Geminids, particularly after midnight on Dec 13-14 and perhaps also early on Dec 14-15 - IF(!!) skies are clear.

The Geminid radiant, close to the northerly "Twin" star Castor, rises around sunset, and reaches a usefully-observable elevation for meteor watchers by about 20h UT from Britain. It then remains well-placed for the rest of the night, culminating around 02h. Sadly, even by Dec 14-15, the Moon will be rising here around 20h too, so Moon-free skies with a properly-risen radiant are not an option this time.

Although Geminid rates are normally good, if lower, for a night or two before, and sometimes a night after, the maximum in an average year, the bright Moon will take the edge off such activity.

For best effect near the peak, watch as much clearer sky as you can comfortably, looking away from the Moon or any surfaces reflecting moonlight, and not too close to the Geminid radiant (partly because the Moon is nearby, but mainly because shower meteor trails are much shorter nearer the radiant, and thus harder to see). This advice applies as well for anyone hoping to try some Geminid imaging.

Geminids are medium speed, often bright, meteors, though few leave glowing persistent trains after them. Much lower Geminid rates should be seen away from the maximum under any moonless conditions between December 4 to 17 from past years' activity.

Good luck!

Alastair McBeath,
Meteor Director, Society for Popular Astronomy.
E-mail: <meteor@popastro.com> (messages under 150 kB in size only, please)
mike a feist
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Post by mike a feist »

13th Dec approx 1938: initially more or less clear sky, enabling location of Uranus for example and then was surprised by a 2nd ? mag, long, swift meteor in Cetus, between Jupiter and southern horizon, moving left to right. Castor and Pollux were well up above the apparent hoizon and this might have been a Geminid but as the Moon then rose twentyminutes later and later on the sky deteriorated eventually to rain, this was the only meteor seen. (NB However did locate asteroid 15 Eunomia - in Perseus at 8.2 and using 20x50 spotting scope on tripod) maf
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Post by Alastair McBeath »

Mike, if it was a notably fast meteor, it probably wasn't a Geminid, as they tend to be more medium-speed on the typical meteoric scale.

Another severe spell in the three weeks of almost endless gales and driving rain last night (Dec 13-14) put-paid to my hopes for a view of some Geminids too here in NE England. Fair bit of damage locally this morning, though not surprising with 80+ mph gusts at times overnight again; still pretty miserable this morning, sadly. However, no foot of snow as we had this time last year - yet...

For anyone similarly disappointed by the UK's skies, the IMO's "live" Geminids page is now up and running, at:

http://www.imo.net/live/geminids2011/ .

The amount of data was limited this morning (Dec 14), but it's still dark over much of North America as I type this (circa 10:45 UT), so more should be coming through in the next few days, hopefully.

Still worth a look this evening for the Geminids if conditions cooperate for once, despite the Moon. I'm not going to even hope!

Alastair McBeath,
Meteor Director, Society for Popular Astronomy.
E-mail: <meteor@popastro.com> (messages under 150 kB in size only, please)
ukmjk
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Post by ukmjk »

I know there is not a lot of 'real' data here, but in case anyone is interested, this was the view from my camera last night....
http://vimeo.com/33651640

Martin K
David Frydman
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Post by David Frydman »

Dear Martin,
That is very nice.
I counted 31 meteors.
Over what time period was this?

Regards, David
ukmjk
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Post by ukmjk »

Recorded between 22:53 on the 13th Dec and 03:19 on the 14th
Cliff
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Post by Cliff »

Dear Martin
A super movie show. I thoroughly enjoyed watching it .
Best wishes from Cliff
The Bat
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Post by The Bat »

I saw 15 tonight (Dec 14th), including two particularly bright ones (not quite fireballs though) over an hour between 21.45 and 22.45. Began to feel the chill setting in, plus the Moon put in an appearance over the neighbour's rooftop, so I decided to come inside at that point.
Nice viewing though and much better than last night's murk, through which I saw the grand total of 2.

Rachel
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cacmcgoo
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14th December, 7.45 to 8.30pm (ish)

Post by cacmcgoo »

Approximately 8 to 12 fantastic sights tonight, and some Geminids I think. One especially superb, slow moving, bright, horizontal, moving north to south, as we piled out of the car ( facing due east). Passed under the twins. As good as a session in Cornwall watching the persieds with friends. One every couple of minutes for the 30 mins i was out in the garden. but they seem to have tailed off by 9 or so.

Really good fun, the kids loved it too.
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ukmjk
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Post by ukmjk »

I watched a good one last night at 11:15 that was about as bright as Jupiter and did a nice slow path across the whole of Orion, top to bottom. Very nice to see!
I didn't pick it up on my camera though, as it was just off the edge of the frame!

Last nights video is here....
http://vimeo.com/33716840

Martin K
Alastair McBeath
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Post by Alastair McBeath »

Good to see a few people had enjoyed some better skies for the Geminids, notably on Dec 14-15. As you may have seen already on the Gallery Forum, SPA Vice-President Robin Scagell was lucky in imaging four Geminids as well, two of which are shown on his photo here:

http://www.popastro.com/phpBB2/viewtopic.php?t=16507 .

There are more comments from some fortunate observers on the UK Weather World's Space Weather Forum, at:

http://www.ukweatherworld.co.uk/forum/i ... nids-2011/ .

The IMO's "live" data page has been suggesting peak ZHRs may have been almost 200 on Dec 14. However, the quantity of observations is not great enough for certainty on this point, plus it's likely the computed rates were inflated because of the bright moonlight. A typical return would seem probable overall, so far.

Unfortunately, British observations have been at a premium once more for this shower, while early comments reaching me from North America have indicated an unusually bad spell of weather across much of that continent too for the Geminids' peak. A normal northern hemisphere winter picture, in fact (so what was the excuse for the rest of 2011?!).

All further Geminid observations gratefully received!

Alastair McBeath,
Meteor Director, Society for Popular Astronomy.
E-mail: <meteor@popastro.com> (messages under 150 kB in size only, please)
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Re: Geminids 2011

Post by Alastair McBeath »

Today it's the Geminids' turn for an update on how they performed last December. Although the shower's maximum has been reliably strong for many years, with a peak likely to last for almost a day at fairly similar ZHRs, the bright Moon and some typically dismal northern winter weather globally meant observers almost everywhere struggled to see much of the shower's best in 2011. However, it has been possible to compile the radio meteor analysis now, which when combined with data from other sources and observing techniques, gives a modest, if incomplete, overview of the near-peak activity.

More visual results were received by the SPA for the Geminids than for most of the other Moon-affected showers during late 2011, albeit many were quite casually made and reported, owing to poor skies across Britain and elsewhere. Even the IMO's "live" online preliminary visual results were quite patchy, indicating a probable main maximum time near 15h UT on December 14. It has remained unclear how accurate the estimated strongest ZHR of 198 ± 13 then really was, since it is possible the value was inflated thanks to the bright sky. Usually, the ZHR would be around 120-130 or so. The timing fell well within the predicted maximum range based on long-term IMO visual studies, expected to persist from roughly 01h-22h UT on December 14.

Intriguingly, the IMO data also hinted at a possible secondary maximum outside this predicted peak period, around 02h-03h UT on December 15, with ZHRs estimated at ~148 ± 13. Casual reports, and comments based on fireball camera observations in America from Bill Cooke (NASA's Meteoroids Environment Officer; helpfully forwarded by Rich Taibi), indicated that the Geminids overall appeared to have been significantly brighter on December 14-15 than 13-14. This was not unexpected, as previous studies going back to the 1960s have found mass-sorting of particles to be present within the Geminid meteoroid stream, meaning brighter shower meteors tend to happen predominantly somewhat after the visual peak.

The IMO's video results for the Geminids (published in "WGN", 40:2 for 2012 April, pp. 69-75, especially pp. 69-70) found only a single, noticeably sharp, maximum at 03:15 ± 15 minutes UT on December 14. As most of the video results were obtained from Europe, there were large gaps in these as well as the visual data, so uncertainties have remained regarding these seemingly discrepant peak timings. It is worth remembering that many video meteor cameras are quite infra-red sensitive, so can detect a range of meteors from the visual down into the sub-visual. Possibly, the video results indicated something of the "fainter meteors" peak earlier in the likely maximum interval.

Using the available radio meteor data from North America and Europe, the SPA's radio analysis found most systems sufficiently active and recording accurately favoured the better Geminid rates as having happened on December 13-14, between approximately 23h-09h UT. Although it is difficult to be certain, it seems plausible there were two stronger phases within this time, from about 23h-01h and 03h-05h UT, the latter perhaps very marginally the better-detected. European radio data collected during the period the Geminid radiant was regrettably undetectable for most of the operational North American observers, also indicated a distinct secondary peak during the interval from ~23h-01h UT on December 14-15 (remembering that the radio meteor results are typically given only in one-hour long data-bins). This included peaks in the few longer-duration echo-count results presented, which would tally with the generally brighter Geminids reported visually on the latter night, assuming as we usually do that longer-duration radio echoes equate with brighter meteors. These factors may explain why the IMO visual results favoured a Geminid maximum on December 14-15, while the video data preferred the previous night. As always when we have too little data to work with, we end up with more questions than proper answers!

The observers whose results contributed to this SPA Meteor Section Geminids review are listed below, including reports sent in directly, posted earlier here or on the Geminids topic of the UK Weather World's Space Weather Forum, or forwarded from the German Arbeitskreis Meteore (in their journal "Meteoros" 15:2, 2012 February, provided by Ina Rendtel; see http://www.meteoros.de ), from the North American Meteor Network by Rich Taibi (see http://www.namnmeteors.org ), from 2012 January's "The Astronomer" magazine via Tony Markham (see http://www.theastronomer.org ) and from Radio Meteor Observation Bulletin 221 for 2011 December, through editor Chris Steyaert (see http://www.rmob.org ). In the list, "R" means radio observations were provided, "Vi" video or other imaging and "V" visual. Where not stated, visual data only were received.

"Alex R" (England), Thomas Ashcraft (New Mexico, USA; Vi), Pierre Bader (Germany), Orlando Benitez (Canary Islands; R), Mike Boschat (Nova Scotia, Canada; R), Jeff Brower (British Columbia, Canada; R), "cacmcgoo" (England), Willy Camps (Belgium; R), Johann Coussens (Belgium; R), Gaspard De Wilde (Belgium; R), Franky Dubois (Belgium; R), Mike Feist (England), "Fujita5" (England), Karl-Heinz Gansel (Germany; R), Luc Gobin (Belgium; R), "Halo" (England), Dave Hancox (Scotland; Vi & V), "HSEA2" (England), "James" (Oklahoma, USA; R & Vi), Peter Knol (Netherlands; R), "Martin K" (UK; Vi & V), Peter Meadows (England; Vi), Sirko Molau (Germany), Sven Näther (Germany), Mike Otte (Illinois, USA; R), "Rachel, The Bat" (England), Jürgen Rendtel (Germany), Steve Roush (Arizona, USA; R), Wayne Sanders (British Columbia, Canada; R), Robin Scagell (England; Vi), Kai Schultze (Germany), Ivan Sergey (Belarus; R), Andy Smith (England; R), Jeff Stevens (England), Chris Steyaert (Belgium; R), Mikhail Svoiski (Arizona, USA; R), Istvan Tepliczky (Hungary; R), Felix Verbelen (Belgium; R).

Many and grateful thanks go to everyone above for your results and comments on the Geminids.

Alastair McBeath,
Assistant Meteor Director, Society for Popular Astronomy.
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