Here is Alastair McBeath’s analysis of the 2011 Ursids :
Following the disappointing run of badly moonlit, and commonly badly weather-affected, meteor showers in late 2011, sadly the moonless Ursids seemed to have done no better for clearer skies, with scarcely no visual reports received by either the International Meteor Organization (IMO) or SPA. However, as the two advance possible maximum predictions noted earlier here were joined barely a day before the event by a third, suggesting peak ZHRs of ~10-15 on top of the usual activity might happen just before 18h UT on December 22, it has been important since to try to establish what may have taken place.
Data from the IMO’s video observations of the shower were discussed briefly in the Organization’s journal “WGN” 40:2 for 2012 April, pp. 69-75, especially pp. 70-71. They indicated just a single sharp peak had been found at 19h UT on December 22, with an estimated visual-ZHR-equivalent of ~15, although being based largely on European results, any events during European daytime could have been missed.
As the Ursid radiant is circumpolar for all our usual northern hemisphere radio meteor observers, located in Europe and North America primarily, it is one of those rare showers whose activity can be followed from all locations throughout the day and night, interference and other technical problems permitting! Carrying out the usual analysis of this data suggested that Ursid activity had probably been present at a radio-detectable level from roughly 02h UT on December 22 through to at least 11h UT on the 23rd. Within that time, the main shower maximum was undoubtedly in the 19:00-20:00 UT interval on the 22nd (remembering that most radio observers provide data in one-hour long recording periods only). It was surrounded by a spell of better than normal, but below-peak, rates from circa 16h-22h. Judging the strength of meteor activity purely from radio data is extremely difficult, although in this case, it was plausible the Ursid activity was fairly normal, so likely close to ZHRs of ~10-15. This was all reassuringly similar to what the IMO video data had proposed.
There appeared to have been several lesser radio maxima as well, although these were generally less convincingly recorded than the main one. Ignoring those which likely resulted solely from better radiant geometry from the two chief geographic regions, those on December 22 around 10h-12h and on December 23 around 07h UT remained as potentially interesting. Unhappily, the lack of other data meant no further investigation of these could be performed.
It remains intriguing that none of the predicted maximum timings coincided at all well with what was actually found, stressing the importance of making observations for as long as possible whenever a meteor shower peak is due, rather than relying heavily on what is “supposed” to happen!
A list of observers whose reports were used in this analysis can be found on the SPA Forum at forum.popastro.com/viewtopic.php
Here is Alastair McBeath’s analysis of the 2011 Geminids:
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 Â± 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!
A list of observers whose data contributed to this report can be found at : forum.popastro.com/viewtopic.php
Here is Alastair McBeath’s analysis of the 2011 Leonids:
With the potential for four Leonid maxima in 2011 scattered across November 16 to 18 inclusive, one of which might have produced activity in the low hundreds, albeit all with a problematically bright waning Moon, it was disappointing that weather conditions for SPA watchers globally seemed to have been unusually poor. Even visual reports to the IMO’s online data page for the shower were unhelpfully thin on the ground, with just four datapoints available between ~18h UT on November 14 through to ~00:30 UT on the 20th. At least for once, it wasn’t just Britain’s weather at fault!
These IMO results suggested merely a single Leonid peak had happened, on November 17-18, when ZHRs reached 22 ± 3. Huge gaps in the data meant this result was especially tentative however, and it would have been very easy for any short-lived outburst, no matter how strong, to have passed entirely unseen. IMO video observations proved less helpful too than might have been hoped (presented in “WGN”, 40:1 for 2012 February, on pages 48-52, especially p. 49), where only a single combined datapoint was determined for each night, based largely on European results. They indicated a single peak on November 18-19, apparently with activity still quite good by the following night. Again though, the broad timescale meant large breaks between these reports.
Looking to the radio meteor results collected by the SPA, even these gave incomplete coverage, since with observers based primarily in central-western Europe and western North America, the Leonid radiant was effectively unobservable, because of being below the horizon for all locations, from about 20h-21h until 00h-01h UT daily, a period into which fell three of the four predicted maximum timings. To hunt for what the data did show, a detailed hour-by-hour examination was made of the radio information available from November 16 to 20, concentrating on when the Leonid radiant was observable from each site. No distinct brief maxima were found on any of these dates, but activity probably due to the Leonids seemed to have been somewhat stronger than normal on November 17, between roughly 02h-13h UT, and was at its strongest on November 19 from about 01h-14h UT. (Remembering that these intervals do not show true peaks, but indicate instead the better-detectable daily period for radio Leonid meteors from the two main geographic regions represented.)
Overall, this radio meteor pattern supported the findings of the IMO video observers much better than those from the visual reports, and implied the better shower activity could have occurred on November 18-19, significantly later than any of the advance predictions had anticipated. In all cases, shower rates were apparently fairly unremarkable, which would in turn infer quite typical Leonid ZHRs had taken place, probably of the order of 15-20 or so at best, much as the visual data found. Any further results from elsewhere would be welcomed still to try to plug the gaps and see if anything unusual did happen in time to any of the late-evening-UT peak predictions.
A full list of observers whose observations were used in this analysis can be found at forum.popastro.com/viewtopic.php
Here is Alastair McBeath’s analysis of the 2011 Orionids :
The latest IMO video meteor analysis of the shower in 2011 (given as part of the October review in the February 2012 issue of the journal “WGN”, 40:1, pp. 41-47, especially pp. 43 & 46) indicated the video peak was observed on the European night of October 23-24, although activity then was only marginally better than on several previous nights, beginning around October 20-21. This sort of protracted, if variable, maximum is relatively common for the Orionids, albeit the stronger peak happening as late as October 23-24 is unusual. The Organization’s preliminary visual data, now updated but still available online at the address given in my October 24 posting above, suggested shower ZHRs were averaging roughly 25 Â± 5 between October 20-21 and 23-24, coincident with the video findings, although the marginally highest ZHR, circa 33 Â± 3 had occurred on October 21-22. This was based on relatively few reports, however.
Scarcely any UK observers had much luck in seeing the shower, and although valuable support came from the Section’s overseas contributors, notably in North America and Germany, there was too little data overall to confirm or improve upon the IMO’s visual findings. Unhappily, the radio meteor observers, who don’t have to worry about cloudy skies, struggled at times with interference across the expected best from the Orionids, which created some rather patchy results at times. Even so, it’s been possible to carry out a reasonably useful analysis of such radio data as was collected by the SPA. As quite often happens with this shower, the rise and fall from the radio maximum was relatively gradual, though the fall seemed more marked than the risen this time. Orionid activity was apparently present at fairly similar levels on October 21-22, 22-23 and 24-25, with a curious drop almost to the pre-peak level on October 23-24. Most datasets seemed to favour October 24-25 as producing the strongest response. However, as with both the IMO video and visual reports, the difference to the other better nights was small.
A list of observers whose results contributed to the SPA’s Orionid files were as follows, including reports sent in directly, posted here or on the Orionids topic of the UK Weather World’s Space Weather Forum can be found at : forum.popastro.com/viewtopic.php
Much later than I’d originally intended while I was still SPA Meteor Director, I’m now starting to catch-up with the outstanding meteor shower analyses from late 2011, hopefully in roughly chronological order!
Four radio observers provided counts of meteor echoes in shorter periods across the Draconid peak as well, lasting between 5-10 minutes, which allowed a more detailed examination of activity in the hours around the maximum. A direct comparison between the IMO’s visual and the SPA radio results showed again a closely similar pattern, with seemingly even many of the minor fluctuations between individual datapoints found in both sets. The radio information also found activity at or above half the maximum flux had been present from 19:20 to 20:45 UT or so, virtually identical to what the video results showed.
This was naturally a very pleasing outcome, allowing further confirmation of what the earlier analyses had indicated.
In Britain, only a few observers in southern England and the Channel Islands seemed to have had any luck in seeing something of the Draconid outburst, and then often far less than they might have hoped. Elsewhere in mainland Europe, conditions were thankfully often much better.
A full list of observers whose data were included in this analysis can be found on the SPA Forum at forum.popastro.com/viewtopic.php
Assistant Meteor Director, Society for Popular Astronomy
2012 June 2
The following summary has been compiled from Alastair McBeath’s posts on the SPA Forum:
Held in Armagh, Northern Ireland,
A Report for the SPA Meteor Section
This meeting of amateur and professional meteoricists from 24 countries was organised by Armagh Observatory. It was the first-ever International Meteor Conference (IMC) in the UK, and also the first time that I’d attended one. The number of attendees was 127 (easily surpassing the previous record of 94). The age distribution of attendees was better than that that typically seen at meetings of UK astronomy groups too. I would, however, have liked to have seen more attendees from the British mainland.
With a large number of people wishing to speak, each speaker was restricted to 15 minutes (including set up and questions). This had the advantage of ensuring presentations were concise and to the point. All presentations were given in English (I wonder how many British people would be able to give a presentation and answer questions in a foreign language?). Sessions were devoted to optical work, the meteoroid environment, visual observations, radio work, fireballs & ablation, astrometry & trajectories, cultural topics and meteor odds & ends. In addition, there were also Saturday afternoon excursions to Armagh Observatory (including taking part in the Human Orrery) and to the Navan Centre (where the residents of the iron-age dwelling welcomed the “wise people who follow the stars”), plus social sessions in the evenings. The participants enjoyed the meteor song and solar system Irish dance performed by local children during a coffee break too!
- Bill Cooke (NASA) describing how amateur observations are used to calibrate meteoroid flux predictions, covering particle sizes ranging from those capable of penetrating spacesuits up to those with potential to cause a loss of the Space Shuttle. He highlighted how the Landsat-5 satellite was sent tumbling on 2009 August 13 by an event which coincided with that year’s third Perseid peak, although, somewhat embarrassingly, none of the published Perseid predictions for 2009 had included the third peak.
- Pete Gural giving an overview of the NASA-funded California All-sky Meteor Surveillance (CAMS) system that is being developed to investigate the belief that 85% of the zodiacal cloud is derived from now defunct comets.
- Praksh Atreya giving an overview of the French Meteor Network (PODET-NET).
- Gerhard Drolshagen reporting on ESA’s investigations relating to meteoroid populations, ranging from infra-red (IR) studies of the zodiacal light, through to lunar crater sizes and, more directly, through studies of impact crater sizes in the Hubble Space Telescope solar arrays returned by NASA.
- Detlef Koschny describing the development of the Virtual Meteor Observatory â€“ a database of 30 000 video-recorded meteors â€“ and illustrated how this has provided improved statistics on shower meteor start heights.
- JÃ¼rgen Rendtel reporting the results of an analysis of more than ten years of video-recorded meteors for the period August 23-October 29. This has resulted in revisions to the dates of maxima and radiant locations for several of the minor showers active during this period.
- Abedin Abedin explaining how numerical modelling had been used to follow the fragments of Comet Schwassmann-Wachmann 3 (which showed 5 fragments in 1995 and more than 70 fragments in 2006) back in time.
- JÃ©rÃ©mie Vaubaillon reporting that various analyses for the 2011 Draconids indicated peak activity will occur (sometime) between 19h and 21h UT on October 8th, favouring observers at European longitudes. The peak ZHR is likely to be measured in the hundreds, but is unlikely to reach storm level.
- Megan Argo describing a low-cost public outreach activity started at Jodrell Bank in late 2006 to record meteors using the forward-scatter technique from a transmitter in Spain â€¦ and how the digital switchover has recently necessitated a switch to another transmitter.
- Jean-Louis Rault summarising the various types of meteor echoes (“Epsilons, Cs, Corkscrews and Co”) detected at radio wavelengths by members of the Belgian VVS meteor observing group. He later combined many of these to produce a short “musical” composition during the traditional Saturday evening cultural session.
- Casper ter Kuile giving a report on the expedition to Sudan to recover fragments from the break-up in the atmosphere of asteroid 2008TC3. Fortunately this had fallen in the north of Sudan rather than the less stable southern part of the country. Around 10kg of material (more than 250 pieces) has been recovered to date.
- Felix Bettonvil suggesting a design for an ‘optimal’ amateur all-sky camera, costing less than 1000 Euros and balancing the needs of astrometry, photometry & velocity determination.
- Anna Kartashova outlining how (using some rather complex equations!) to derive celestial coordinates of meteor events registered by TV systems.
- Eliska Anna Kubickova reporting the results of attempts to use “computer vision” to search for meteors in images. Although there were some cases of spurious identification, around 80% of meteors were successfully detected.
- David Cullen outlining a proposed mission to generate hypervelocity meteoroids by sending particles of known mass and composition on a lunar free return trajectory â€“ this could be one component of an ESA medium-sized mission opportunity.
- Damir Segon describing how astrometry often seems to overestimate the speed of very bright meteors, leading to a larger than expected scatter in calculated semi-major axes. Inspection of individual video frames often shows asymmetry in the heads of such meteors, which may be partly due to effects within the optical system.
- David Asher & John McFarland giving an overview of the work of E J Ã–pik. Ã–pik had worked from Arizona in the 1930s to record large numbers of meteor images, which he subsequently analysed when working at Armagh in order to calculate their orbits.
- Mike Simms giving an overview of the three 20th century Irish meteorite falls at Crumlin (1902), Bovedy (1969) and Leighlinbridge (1999). Analyses indicated that all three meteorites were originally part of planetoids that had been large enough for melting and differentiation to have occurred. Compositions suggested the Bovedy meteorite was derived from near-surface material, whereas the other two were from deeper levels.
- Apostolos Christou describing the Armagh Observatory meteor cameras. This system has been in operation for 5 years from sites at Armagh and Bangor (NI). In 16 250 hours of operation (averaging 3 hours usable sky per night), this has recorded 6309 single station meteors and 1281 double station meteors of which 53 were fireballs of magnitude â€“4 or brighter, 25 of which were associated with meteor showers.
- Sylvain Bouley outlining the development of an international network to monitor lunar meteoroid impacts between last quarter and first quarter lunar phases. Flashes recorded to date have been in the magnitude range +3 to +10 â€“ the latter limit is surprising since the equipment used is capable of detecting fainter flashes.
- Attendees from Venezuela, India and Nepal describing their attempts to encourage meteor observing in their respective countries.
- Nagatoshi Nogami providing a translation of a meteorite poem from ancient China.
- Rainer Arlt suggesting possible areas for future work, including monitoring for meteors in the 8-10 micron IR window and investigating radio radiation from meteors. There is also a desire to encourage more meteor observing from Africa.
- Mark Gyssens giving an overview of the IMO membership and finances. Although there was the inevitable dip after the Leonid storm years, membership has since increased from 192 in 2005 to 244 in 2009, and is now 261. The IMO is now offering an electronic-only subscription. Members who choose to receive WGN electronically benefit from a 5 Euro reduction in their subscription.
In summary, I would say that I very much enjoyed the meeting. It was a great opportunity to meet many people who I had previously only known by name. I would recommend future IMC meetings to anyone who is able to attend.
Tony Markham, SPA Meteor Section Assistant Director
Tony Markham is a long-time SPA member and contributor to the work of the Meteor Section. He became an Assistant Director to the Meteor Section in the early autumn of 2010. He also formerly directed the SPA’s Variable Star Section
Observations of the December 8-9 fireball arrived from 76 places across the country, as demonstrated by the accompanying sketch map, showing most of mainland Britain. The red dots indicate sites from where reports were received, though sometimes one dot may represent several observers too close together to show separately at this scale. The red arrow gives the more probable best-estimated projected surface track for the fireball, referred to below as the “centre line”, while the shaded red oval surrounding it is the area within which the meteor most likely occurred, to give an impression of the errors involved in determining the centre line. As the data available did not all confirm a single pattern for where the meteor may have been, the following discussion relies on the region and path which gave the higher probabilities only. The most certain aspect is that the fireball had a generally east to west trending trajectory above northern England. Its start point most probably occurred above County Durham, North Yorkshire, the East Riding, or the North Sea offshore of there, or perhaps parts of the adjacent English counties. The centre line looked to have begun at around 105 km altitude just inland of the North Yorkshire coast, about 7 km northwest of Scarborough (around 54.3Â° N, 0.4Â° W). The visible end was then plausibly over western North Yorkshire, western County Durham, northeast Lancashire or southeast Cumbria. Again using the centre line, an end point near 54.3Â° N, 2.0Â° W can be proposed, over northwest North Yorkshire, likely at around 60 km altitude above the eastern Pennines of upper Wensleydale near Aysgarth. Orders-of-magnitude for the errors on these positions from the centre line were at least +/-+/- 0.75Â° error on the geographic coordinates. Remembering the centre line was not definitive, and merely drew on what most of the reports would at least partly support, if we assume it to have been approximately correct, the projected surface path would have been ~105 km long. The fireball’s atmospheric trajectory would then have descended at about 23Â°-24Â° to the horizontal (or between about 13Â° to 30Â° dependent on the error margin), giving an atmospheric path length of ~115 km (or between 108-124 km). Estimates for the object’s visible flight ranged from 1 to 10 seconds, according to those who saw all or most of the event, but most (85%), including the few more experienced astronomical observers, favoured a duration of six seconds or less, the majority (68%) between 2 to 4 seconds, with an overall average for all the estimates of 3.9 seconds. Using this average with the atmospheric path lengths proposed above gave an atmospheric velocity for the meteor, not allowing for deceleration, of ~29 km/sec (error range ~28-32 km/sec), so meteorically slow. This was consistent with the relatively low start height, as slower meteors tend to ablate lower in the typical ~90-120 km altitude meteor zone. With the path direction and length, the meteor was likely a sporadic or possibly a late Northern Taurid (recent International Meteor Organization video results have indicated the Northern Taurids probably continue their activity until December 10, rather than ending in late November as had been long supposed). The path direction would have to have been much more northeast to southwest, the estimated velocity somewhat swifter, the path length greater and angled more shallowly to the horizontal for the event to have been a potential Geminid, given that that shower’s radiant had barely risen to the northeast when the meteor happened. Forty-three observers commented that the object broke apart, probably in a severe fragmentation event quite late in its apparition, producing around 4 to 8 main pieces and likely a lot of smaller sparkling droplets. Ten people suggested the meteor had left a short-lived persistent train for around two seconds, though three people saw no train at all (possibly because of different local observing conditions). Colours mentioned in the main fireball included white (34%), green (20%), orange and yellow (17% each), blue (11%) and red (1%), while those in the tail or the persistent train (not everyone was clear about the distinction) were orange (27%), blue (21%), yellow and white (16% each), green or red (10% each). Nobody in the open air reported hearing any sounds associated with the meteor. The lack of acoustics and the relatively high end height counted against the possibility of any meteorites having fallen from the event, and increased the difficulty of identifying the more likely fall zone. Any solid objects continuing along the centre line would have splashed-down into the Irish Sea between the Man and Cumbrian coasts, around 20 km offshore of Maughold Head, easternmost point on the Isle of Man. The minimum potential fall zone, making allowance for the suspected errors on the meteor’s estimated trajectory, but not for atmospheric effects, such as wind or drag, would have covered the Irish Sea (the largest single target) or the adjacent lands between the western end of the centre line over western England, north to southwest Scotland, west over the Isle of Man to eastern Northern Ireland and the extreme east of Eire, and south across north Wales. No fall reports from within this area were received, however. Some of the initial sightings can be found on the SPA’s Observing Forum and the UK Weather World’s Space Weather Forum topics for this event, with several briefer reports on a BBC News webpage , and from The Daily Telegraph online. Two video images have been located. One was on YouTube, taken from Knotty Ash near Liverpool inside a moving vehicle, but which showed probably a good part of the flight (and which was used to help refine the fireball’s potential occurrence zone here). The other was caught by an automated all-sky camera run by Cambridge University, where a flash of light from the meteor occurred on the dome in shot at 17:34:14, with the tree below lit up too from the reflected flare.
2010 December 08-09 17:36 +/- 5 min. Fireball Path
The sighting of the December 9-10 near-sunset fireball was posted on December 9 by “equaitca” on the SPA’s Observing Forum topic about the December 8-9 event.
Four visual sightings timed, sometimes quite imprecisely, between 20:35 and 21:00 UT later on December 9-10 indicated another multi-site fireball for southern England. The witnesses were in Oxfordshire, Hertfordshire, East Sussex and the London/Kent border, while the University of Hertfordshire’s Niton camera also recorded it (the image is available on the Observing Forum topic discussing this fireball). An attempt to triangulate the reports met with only limited success. However, the fireball was plausibly over the near-coastal Pas de Calais-Flanders area of northern France to northwest Belgium, between roughly Boulogne, France to Nieuwpoort, Belgium. It may have been partly over the Channel too, probably following a path angled somewhere between south-north to southwest-northeast. For these rough paths, start heights of around 105-85 km could be suggested, though the end heights came out quite low, around 45-35 km, which may indicate the computed path was somewhat in error, particularly around its end.
The ~22:00 UT fireball on December 14-15 was reported by “Charles” (posted 2010 Dec 16) on the Observing Forum’s “Geminids 2010” topic.
Alastair McBeath, SPA Meteor Section Director
Address in Popular Astronomy