Update on three Leonid fireballs

Here are updates on three fireballs that were mentioned in the  initial Leonid report

2017 Nov 13th  04:31 UT

Bill Ward has generated this graph which compares the spectrum of this fireball with a spectrum captured by William Stewart of the fireball on Nov 19th.

As can be seen, there is a good match between the strengths of the main emission lines.

Bill notes that the divergence of the two plots towards the left and right ends is most likely due to vignetting in the images related to the positions of the spectra relative to the edges of the images (i.e.the parts of the spectra in each image near the edge of the field of view were recorded fainter than they were in reality)

 

2017 Nov 19th  02:29:06 UT

The image to the right shows this fireball, as recorded very low in the ENE, close to the start beta Leonis, by the Bayfordburycamera of the Univ of Herts all-sky fireball monitoring system http://www.star.herts.ac.uk/allsky/

Despite poor observing conditions, Eric Anderson (London) also captured an image of this fireball near the edge of his camera’s field of view.

Paul Sutherland (Walmer, Kent) has created a video from his individual images which shows the decay of this fireball over 25 minutes (speeded up).

The video can be viewed via this link

https://twitter.com/skymania/status/933010467882242050

 

2017 Nov 19th  05:47:05 UT

 

Further images of this fireball, in addition to the one by William Stewart, previously mentioned, have now come to light.

 

The first image shows the fireball in the NE sky, travelling from Camelopardalis to Cepheus, as captured by the Bayfordbury camera of the Univ of Herts network.

The second shows the fireball image captured by Alex Pratt (Leeds), producing a terminal flare as it heads from Leo into Virgo.

Another image was captured by Ray Taylor of the NEMETODE network, who lives at Skirlaugh in East Yorkshire. In the image, the fireball is approaching Ray almost head on.

Despite poor observing conditions, Eric Anderson (London) also captured an image of this fireball

Interestingly, whereas the software being used by William and Alex classified the fireball as a Leonid with a terminal flare of mag -7, the software classified Ray’s fireball as a mag -7 sporadic.  However, this may have been a consequence of the very short sky path in Ray’s image.

Based on the sky positions in the images captured by William and himself, Alex has determined the trajectory of the fireball to have been over the east midlands, as can be seen here.

The analysis indicated that the fireball became visible at an altitude of about 127 km and ended at an altitude of approx 84km.

This trajectory may be need to be adjusted slightly when a further image captured by Nick James (Chelmsford) has been taken into account.

 

Given the time of the night, it is not surprisingly that there has been a lack of visual reports of this event.

The only possible visual sighting that has come to light so far was by Tracie Heywood (Leek, Staffs) who noticed a bright (though not mag -7) Leonid in Ursa Major just as she stepped out of the house at approx this time to check on the sky conditions (which were clearish sky with a veil of thin cloud)

2017 Leonids

With New Moon occurring on November 18th, skies were set to be moon-free for the 2017 Leonid peak.

Although a quite good meteor shower, the Leonids do provide some challenges.

Most significantly, the Leonid radiant doesn’t rise above the horizon until around 22:30 local time and so no Leonids can be seen early to mid evening. Observed rates before midnight are inevitably rather low and so visual observers (if they have clear skies) have to choose between starting late evening and patiently waiting for rates to rise as the hours pass, or dragging themselves from their warm beds in the early hours of the morning when the radiant has climbed earlier.

For imagers, there is also the issue that Leonids are fast moving and thus deposit less light per pixel as they cross the camera’s field of view.

The Leonid period can also often be cloudy, but in 2017 many parts of the UK enjoyed some overnight clear spells during the nights around Leonid maximum, allowing some impressive results to be obtained.

Nov 12-13

The first Leonid report came from Bill Ward (Kilwinning) who captured this image of a bright Leonid at 04:31 UT on the morning of November 13th.

The image shows it moving away from the ‘sickle’ of Leo (which is where the Leonid radiant is located).

Bill has also posted a video clip which shows the fireball, its associated persistent train and a spectrum of the fireball that contains a number of ‘forbidden’ spectral lines from oxygen, including the green line at  557.7nm.

The video can be viewed  here

‘Forbidden’ spectral lines are spectral lines that are not seen under normal conditions near the Earth’s surface, but can be seen in much less dense environments, such as is the case high (above 110km) in the Earth’s atmosphere. Meteor showers, such as the Perseids and Leonids, that produce faster meteors are more likely to be visible at such altitudes.

 

Only around an hour later, Alex Pratt(Leeds) captured this image of a magnitude -3 Leonid via his NW facing camera.

In the image, Perseus is near the top and Auriga is near the bottom, with the Pleiades being just above the brightest part of the meteor.

 

Nov 16-17

Tom Banks (Comberbatch, Cheshire) carried out a visual meteor watch between 23:08 and 01:08 UT, recording 4 Leonids, 2 southern Taurids and three sporadics (LM 5.0).  The brightest meteor was a mag -2 blue-green Leonid at 00:43 UT that passed through Ursa Major.  Attempts at a second watch, starting at 01:28 UT, was soon frustrated by increasing cloud, with no further meteors being seen.

 

Alex Pratt (Leeds) captured this image via his NW facing video camera of a Leonid fireball as it passed through Auriga at 06:28 UT on the morning of November 17th.

The fireball was also imaged by Mike Foylan (Rathmolyon, Ireland), another member of the NEMETODE network.

Triangulation of the sky paths recorded in the two images revealed the fireball to have had an atmospheric trajectory above Morecambe Bay.

It also showed that the fireball became visible at an altitude of around 127km and terminated at an altitude of around 95km.

The fireball was probably about magnitude -4.

Alex also reports that a good number of Leonids were recorded by this N and NW facing cameras (SE facing camera yet to be checked).

 

Nov 18-19

Cloud seems to have been much more extensive during the night of Nov 17-18 and no reports have been received so far.

The night of Nov 18-19 produced clearer skies with a weather front clearing towards the south west as the night progressed. Tom Banks (Comberbatch) and Tracie Heywood (Leek, Staffs) both reported skies becoming clearer in the early hours of the morning, but with clearances not being sufficiently prolonged to allow useful meteor watches. Tom finally had clear enough, though hazy, skies by 04:35 UT and saw 4 meteors (3 Leonids, the fourth probably being a Taurid, LM 4.8) before haze and twilight became too big a problem by 06:15 UT.

Automated imaging systems, were less adversely impacted by the variable cloud, being able to simply exploit any clear skies that occurred.

Although the Leonids had passed their peak, they still produced (at least) two more fireballs.

One, at 05:47 UT, possibly of magnitude -6, has been reported by William Stewartof the NEMETODE network (http://nemetode.org/index.html ).

In addition to imaging the fireball itself,  William also imaged its spectrum and detected the radio reflection, shown here, from its ionisation trail.

Another NEMETODE member, Michael O’Connell, also reports having picked up the radio reflection from Ireland.

An image of a bright meteor passing through Cepheus at this time was recorded by the Bayfordbury camera of the Univ of Herts all-sky system. The image can be seen  here.

Paul Sutherland (Walmer, Kent) captured this image of a bright Leonid at 02:30 UT(Paul suspected that it was probably a fireball, but he didn’t see it visually and so no magnitude estimate was available).  The image was secured using a Fujifilm X-M1 camera with a Samyang 12mm f2 lens.

In reply to Paul’s Facebook post about this fireball, Koen Miskotte reported that the fireball was also imaged from several locations in the Netherlands and was probably about magnitude -8 … and so was easily within the fireball magnitude range.

More images of this fireball, timed more precisely at 02:29:08 UT, can be viewed  here

The fireball’s trajectory will have been over the southern North Sea

An additional image of this fireball, low in the ESE sky was captured by the Bayfordbury camera of the Univ of Herts network. The image can be viewed  here

Paul has also supplied additional images showing the persistent train slowly fading and drifting across the stars of Coma Berenices.

The lower left hand image shows the train a few seconds after the meteor; the lower right image shows it 10 minutes later.

Notable Meteors & Fireballs : 2017 Sep-Oct

Here, in reverse chronological order, is a summary of notable meteors and fireballs reported during September and October:

2017 Oct 31st  06:12 UT

This fireball was reported by Anne James-Burns (Eccles).  The fireball had a duration of 1-2 seconds and was descending in her southern sky, leaving a short-lived train.

Additional reports of t his fireball were made to the IMO and can be viewed  here.  A preliminary analysis by the IMO suggests that the fireball was located over the Bristol area.

 

2017 Oct 26-27 : a busy night for Bill Ward

Having been clouded out for the previous 3 weeks, Bill Ward (Kilwinning) made very good use of clear skies on the night of Oct 26-27.

He reports that he captured images of 239 meteors (additional meteor-like images were eliminated as they were due to satellites, cosmic rays, etc).

Some of the meteors imaged show interesting light curves, a good number being double peaked.

In some cases, the first peak was the brighter one; in other cases, as in the accompanying image, it was the second peak that was brighter.

Bill also captured spectra of several meteors, including an iron meteor for which he comments that its light curve showed the bright onset that seems to be typical of such meteors.  The colourised image (just covering the violet to green part of the spectrum) is shown below:

 

2017 Oct 21st  04:09 UT (05:09 BST)

Extensive cloud during the nights around Orionid maximum meant that conditions were rather unsuitable for visual observing. Observers who operate automated video cameras could, however, leave their systems running and let them catch any meteors that happened to appear during short lived cloud breaks.

One such meteor was this Orionid fireball, which was imaged by William Stewart (Ravensmoor, Cheshire) and two other members of the NEMETODE group. William also captured part of its spectrum as can be seen to the bottom right of the accompanying image (the breaks in the image of the fireball itself are an artefact of the conversion of the video image to a still image).

 

With the fireball having been imaged from three locations, it was possible to triangulate its atmospheric trajectory and to determine its ground track.

 

As can be seen from the accompanying diagram, this was over the southern Pennines with the fireball heading in a roughly south to north direction (the Orionid radiant being in the southern sky at the time).

 

The fireball was probably around magnitude -5.

 

More images from the Orionid period can be seen in the   main Orionid report

 

TA Awards

Congratulations go to regular contributor Alex Pratt, who has been awarded the 2017 George Alcock award, as voted for by readers of The Astronomer magazine. The award is given to the person who has made the best contribution to the magazine over the previous 12 months.

Another NEMETODE member, Denis Buczynski, received the magazine’s 2017 Alan Young award, for his images submitted to the magzine over the same period, the highlight being an image captured from Tarbatness in northern Scotland that showed a spectacular fireball at 00:36 UT on 2017 Jan 22, appearing above an auroral arc.

 

2017 Sep 14th 05:09 UT (06:09 BST)

This fireball was witnessed by Elliot Carpenter (Longbenton, Newcastle upon Tyne) in his eastern sky. He described it as being bright green in colour and having a duration of 1-2 seconds.

The fireball was also witnessed from a number of locations across northern England, the London area and the Netherlands. Winesses in the Netherlands saw it in their north western sky while those in the London area saw it in the northern sky. All of this fits in with the fireball being over the north sea and closest to NE England.  These additional reports of this fireball can be viewed  here

No images of the fireball have come to light so far. This is probably due to the fireball occurring when the twilight was rather bright and hence most automated camera fireball systems would have already “switched off” at the end of the night. Experience also shows that video cameras tend to perform less well than the human eye at picking up fireballs in twilight conditions.

 

2017 Sep 9th  22:43 UT (23:43 BST)

Alex Pratt (Leeds) captured this image of a September Perseid fireball above the stars of the Plough at 22:43:15 UT  via his north facing video camera.  This “still” image has been created from the original video and the breaks in the fireball along its path are related to this conversion, rather than being properties of the fireball.

Alex also adds, however, that the camera involved operates indoors and is looking through double glazing and this has led to the additional artefact of the parallel line below the fireball.

 

(the September Perseids, not to be confused with the Perseids of August, are a minor meteor shower active during the first half of September which peaks on September 9th).

 

2017 Sep 5th  22:09 UT (23:09 BST)

Tony Quinn (Winkley, North Yorkshire) reported a fireball that he saw through cloud and cloud gaps. The fireball, probably about magnitude -6, was in his north western sky and heading north.  He describes it as fragmenting as it descended from around altitude 60 deg to altitude 20 deg and leaving a long train.

The fireball was also seen from a number of other locations, with most witnesses being in central and eastern Scotland.  Unfortunately, almost all witnesses seem to have been on the eastern side of its atmospheric trajectory and this makes it tricky to accurately determine that trajectory.  However, it seems likely that the fireball started over the Kintyre/Isle of Arran area (or possibly a little further south) and headed in a roughly NNW direction along the west coast of Scotland towards Mull.

Additional reports of this fireball can be viewed  here

A very favourable year for the Geminids

Weather permitting, 2017 should be a great year for observing the Geminids, with peak activity due to occur durig the night of Dec 13-14 (Wed-Thurs). Geminid rates will also be quite high during the night of Dec 12-13 and also fairly good during the nights of Dec 11-12 and Dec 14-15, but do be aware that rates drop off quite steeply in the nights after maximum. Read more

2012 Perseids

After a moonlit Perseid maximum in 2011, we had hoped to see many more Perseids in 2012. Observations of the early Perseids would be hindered by the Full Moon of Aug 2 and the Moon would be slow to move out of the evening sky afterwards. However, by Perseid maximum, the Moon would only be a waning crescent and thus more of an irritation in the later part of the night rather than a hindrance.

Unfortunately, the clouds didn’t cooperate and clear skies were scarce. However, detailed visual reports were submitted by Alastair McBeath (Morpeth Northumberland), Graham Winstanley (Bassingham, Lincs), Jane Mills(Thrapston, Northants) and Tony Markham (Leek, Staffs) and radio results were submitted by Alan Heath. Summaries of visual results were also posted on the SPA Forum by Mike Feist (Portslade, Sussex), Robin Scagell(Flackwell Heath, Bucks), Kevvek (East Devon) and coldfieldboundary (Bruges). For further details, see forum.popastro.com/viewtopic.php

Peter Meadows (Great Baddow, Essex) was able to capture images of several bright meteors during the Perseid period using his video system. The images below show a Perseid at 23:55 UT on Aug 4 and a southern Delta Aquarid at 23:33 UT on Aug 11.

Fortunately, we can find out what we missed by looking to reports from around the world submitted to the International Meteor Organisation (IMO). Their activity curve (see imo.net/live/perseids2012/ ) suggests a peak ZHR of around 100 during the daytime of Aug 12, in line with predictions.

Fireball Reports from 2012 August

The poor UK weather in the first half of August not only severely hindered observations of the 2012 Perseids, it also meant there was little opportunity to see any fireballs. Consequently, August’s fireball reports were all from the second half of the month.

Richard Stratford (Letchworth, Herts) reported a bright meteor (mag -1 or -2) at 0107 GMT on Aug 19. Although the date is close to the maximum of the Kappa Cygnid meteor shower, the sky positions quoted show that it was a sporadic meteor.

Jeffrey Sutton (Bromsgrove, Worcs) reported a fireball, possibly of mag -6, at 2232 GMT on Aug 20 and heading south in his south western sky. Although the date coincides with the maximum of the Kappa Cygnid meteor shower, the sky positions quoted show that it was a sporadic meteor.

Philip Carden (Winsford, Cheshire), Dave Blackhurst (Liverpool) and Stephen Dews (Wakefield, West Yorks) reported a fireball at 2215 GMT on Aug 27. This fireball was widely seen by people from northern England down to southwest England and produced sonic booms over South Wales. There are also many reports in the press regarding this fireball. Some examples (note that the images they contain are not of this fireball) are :

www.southwalesargus.co.uk/news/9896319.CWMBRAN_BIG_BANG__Causes_a_stir_on_Twitter/

menmedia.co.uk/manchestereveningnews/news/s/1587450_hundreds-witness-meteor-shooting-across-skies-of-greater-manchester

www.telegraph.co.uk/science/space/9503248/Exploding-meteor-creates-sonic-boom-over-Wales.html

www.dailymail.co.uk/news/article-2195053/Meteor-explodes-Cwmbran-Wales-wakes-families-sonic-boom.html

Peter Grego (St Dennis, Cornwall) observed an impressive fireball at 2224GMT on Aug 30 in bright moonlight. His description of it reads : “First seen come into view as bright single orange point in south at altitude of around 40 degrees to the west of the near full Moon, almost instantaneously brightening to magnitude -3. Continued brightening to about magnitude -6 as it passed around five degrees south of Vega at an altitude of around 60 degrees, leaving bluish track about 10 degrees long in its wake, fragmenting but retaining brilliant core. Disappeared into bank of cloud in northwest at altitude of about 30 degrees. No sound heard. Visible for around 12 seconds.”

There are also a number of fireball reports on the website thelatestworldwidemeteorreports.blogspot.co.uk/ , from witnesses in Devon, Hampshire, Wales, Shropshire, Merseyside and Cheshire that probably also refer to this fireball.

2012 Sep 21 fireball

This spectacular, long duration, slow moving fireball was visible over much of the UK (and further afield) shortly before 11pm BST on the evening of Friday 21st September 2012.

Updated Analysis (2012 Oct 23)

Alastair McBeath has now been able to carry out a more detailed analysis of the fireball:

Reports: The total number of separate reports I’ve collected (including videos, images and visual sightings) comes to 990. Forty of these included videos or images. Ninety-one reports were from sites which could not be located, either because the witness provided insufficient, or only ambiguous, information (“Holywell” is not a single location, people…).

Occurrence Time: From the Norway imaging evidence and details from the Netherlands, the fireball probably began at 21:55 UT over northern Germany. Assuming the visible trail lasted between two to three minutes would mean it likely crossed Britain and Ireland around 21:56-21:57 or so. However, the timing estimates by the observers were often far from this, with many failing even to give a BST or UT notation, where that would have been appropriate. The AMS reports especially featured all manner of American time zone abbreviations despite being made from Britain and nearby. In compiling the data, I assumed where possible the times were meant to be around 21:55 UT. There were obvious problems in doing so, and the overall range of timings converted to UT from what was claimed as BST ran from 19:15 to 00:10 UT for what, judging by the descriptions, must have been the same fireball. The mean from all of these was 21:58.3 UT (920 estimates), with 84% falling within ten minutes of 21:58, and 72% within five minutes of it. Given the longevity of the event, this may more closely represent the estimated end time for the fireball, rather than its start.

Visible Duration: Many observers (675) provided estimates for how long they were able to see the event. These ranged from 2 to 300 seconds, the latter almost certainly an exaggeration. The average from all was 18.9 sec. All the observers clearly saw only part of the trail, and while this mean duration may say more for the individual’s limited view of the sky, it may also provide a crude ball-park figure relating to the readily-visible interval during which the meteor passed across the British Isles. Most reported estimates (83%) fell between 10 to 60 seconds, 76% within 10 to 30 s. Just 9 reports favoured a visible time of over sixty seconds.

Estimated Magnitude: Many people only made comparison with the Moon or Venus, with the AMS reports and those from the Lunar Meteorite Hunter blog especially favouring such comparisons. A substantial number (unrecorded) claimed the event had been of Sun-like or greater brilliance. As there were no reports of blindness, temporary or otherwise, and taking into account the generally normal video and image recordings, such extremes were discounted from further analysis. In general, I assumed a conservative brightness level where leeway was available. For example, given that the waxing crescent Moon had been readily visible in the evening sky up to a couple of hours before the meteor occurred, I assumed any comparison with the Moon meant the crescent Moon that evening, unless otherwise indicated. A further problem was that the fireball had broken up into multiple pieces during its passage over Britain, so it was not always clear exactly what people were estimating the brightness of. However, from 381 surviving estimates, a mean magnitude of -9.7 was derived, the range overall from -2 to -15 (all “brighter than full Moon” estimates which made no mention of the Sun went into the -15 bin). From the more experienced descriptions, I would suggest a range from magnitude -8 to -11 would cover the probable brilliance of the object(s) as observed.

Colours: For what it’s worth… A total of 1374 colour estimates were made (most people described more than one colour as present in some part of the event), with the division as follows: Red = 10%, Orange = 32%, Yellow = 17%, Green = 14%, Blue + Violet = 3%, White = 24%.

Derived Angular Velocities: I extracted information from those reports where details had been provided on the first and last points of the visible trail observed, and where an estimate had been made for how long the object had remained visible, in hopes of determining angular velocities for different parts of the visible trail. Unfortunately, only 23 reports included all this information, which after computation gave a range from 0.1 to 18.7, and a mean of 5.4, degrees per second. Most (74%) fell in the range from 1.5 to 9.5 degrees per second (mean 4.6), with 52% in the 2.5 to 8.5 °/s range (mean 5.1). Despite this, as only one of these observations was made from Ireland, this may give a ball-park range of values for the apparent angular velocity as the meteor passed over mainland England.

* Estimated Trajectory Across the British Isles: (see www.popastro.com/meteor/reports/report.php for a map).  Analysing reports from 66 identifiable locations of where the meteor was claimed as having passed overhead, or almost so, using the usual methods of ignoring extreme outliers and attempting to reconcile as many of the remaining sightings as possible, a central-line surface track for the estimated overhead-flight line was determined. It seems likely that the actual ground track probably fell within approximately fifteen kilometres of this line, as a best-estimate. Moving east to west with the meteor, the following identifying points can be listed:

1) Crossed the English North Sea coast just north of Scarborough town centre, and passed over the southern extent of the (northwest-)adjacent village of Scalby, North Yorkshire, around 0.39°W, 54.3°N;

2) Passed overhead at Northallerton, North Yorkshire and Windermere, Cumbria;

3) Crossed the English Irish Sea coast west of a point immediately south of Sellafield railway station, Cumbria, circa 3.5°W, 54.4°N;

4) Passed about one kilometre offshore to the north of Point of Ayre, off the Isle of Man;

5) Crossed the Northern Ireland Irish Sea coast at Cloghy (about 2.5 km south of Portavogie) on the Ards Peninsula, County Down, at about 5.45°W, 54.44°N;

6) Crossed over Strangford Lough at Ardkeen (east shore of Lough);

7) Passed overhead almost exactly midway between Lurgan and Craigavon, County Down;

8) Passed overhead at Ballygawley, County Tyrone;

9) Passed above the neck of the narrows of Lower Lough Erne, County Fermanagh, and the middle of Lough Melvin at the Counties Fermanagh-Leitrim (also Northern Ireland-Ireland) border;

10) Crossed the Atlantic coast of Ireland west of Cliffony, County Sligo, approximately 8.47°W, 54.43°N;

11) Passed overhead of Inishmurray, about 12 km offshore of the Sligo coast.

End of Visible Flight: I extracted data from those visual observers who gave numerical end point estimates where the altitude was 10° or less only, in the hopes of determining the possible end point for the visible trajectory from the British Isles. Regrettably, only eleven such reports could be found with identifiable locations, and of those, it was apparent that just three fell even close to identifying a point off the central-western Irish Atlantic coast. These three were Leeds in England (az. 269°, alt. 0°), Waterloo, Perthshire in Scotland (az. 250°, alt. 10°) and Birdhill, County Tipperary in Ireland (az. 281°, alt. 10°). Given the problems in analysing small-angle altitudes, I used only the azimuths to determine a possible end-point bearing, and found that curiously, as far as my simple graphical map-plotting suggested, these three bearings came within about 40 km of crossing with one another near 15.6°W, 53.6°N, roughly 360 km offshore of Achil Head, Achil Island, County Mayo, Ireland! While quite a surprise, I think it would be best to treat this result with considerable caution, but it may perhaps serve as a temporary benchmark until more data from the trajectory calculations are available.

Associated Sonics: Thirty-one acoustic and twenty-one electrophonic reports from 56 claims of sonics associated with the fireball had locations given, allowing me to plot them out with the “overhead” reports and meteor’s ground track.
 
Acoustics: There was no clear pattern in the acoustic reports of when the sounds were reported as heard in relation to the observer’s position regarding the trajectory. For example, the greatest concentration of such reports was in northeast England (eight reports from the coastal plain between the Rivers Tees to Blyth valleys), yet within 25 km of one another, observers at five sites in County Durham alone noted delays from 30 seconds to 300 seconds, with no consistency apparent. However, all but two such reports were from within 60 km of the central line of the proposed surface track, with only one report from anywhere west of Armagh, Northern Ireland, at Dromahair, County Leitrim in Ireland. That several reports of acoustics were from the northeast coast of England, or very near it, may suggest the fireball was beginning to fragment while still out over the North Sea, assuming these sonics were linked to fragmentation within the incoming meteoroid. The ship around 190 km off Cleethorpes, Northeast Lincolnshire, reported “flickering light when it was passing over the ship”. If that was the start of the fragmentation, it might have begun around 130-150 km off Flamborough Head, East Riding, assuming the ship was heading roughly northwest (the sighting was from the bridge), and that “passing over” meant over the ship’s central line/direction of heading.

Electrophonics: Curiously, all the reports of electrophonics in England and Wales were from south of the projected surface track, the nearest no closer than 40 km from that line, and the furthest (Daventry, Northamptonshire) nearly 230 km distant. In Scotland, only two such reports were made, both from in or near Glasgow, about 140-150 km to the north, while in Ireland there were only three electrophonic reports at all, two in eastern Northern Ireland (at Newtownards, County Down and Newtownabbey), one in eastern Ireland at Slane, County Meath. Given the descriptions of what was heard, it seems likely most of these were genuine observations of simultaneous sounds, and in England at least, there was a mild concentration somewhat closer to the meteor’s projected ground track (albeit caution is needed here, as this was also in the area of greater population densities around southern Lancashire-Greater Manchester-South and West Yorkshire).

Any more reports ?

If you saw the fireball, but haven’t reported it yet, please do so as this will help fine tune the details further. You can either send an email to meteor@popastro.com or via the SPA Fireball report form : www.popastro.com/meteor/fireballs/reportform/index.php 

The three key elements to mention in any fireball sighting are:

1) Exactly where you were (give the name of the nearest town or large village and county in Britain);

2) The date and timing of the event (remembering that British Summer Time is still in operation, so subtract one hour from current clock time to give this in Universal Time = Greenwich Mean Time); and

3) Where the fireball started and ended in the sky, as accurately as possible, or where the first and last points you could see of the trail were if you didn’t see the whole flight.

If you’ve already submitted a sighting, many thanks! If you provided an active e-mail address, a reply will be sent in due course, but with a large number of reports in addition to the Section’s usual correspondence-load, aside from further analysis of this fireball, there may be a delay. Your data is much appreciated despite that, however!

Observer comments

Here a selection of observer descriptions of the fireball :

David Graham (Barton, N Yorks) : The object rapidly expanded to show a visible disk with a green hue, and was several times brighter than Venus … it passed through my zenith and appeared to be trailing a succession of fragments as it did so. It was seen disappearing over the western horizon as a cluster of glowing fragments, very much like a spent firework …  I would state that the track was Aries, Andromeda, Cygnus and Hercules

Adam Smith (Waterloo, Perthshire) : It started as a large white ball and train, fragmenting to multiple orange balls travelling to the west at a consistent altitude.

Gloria Latham (Durham) : Approached in a green bright light, as it went overhead it broke into several fragments, the main body remaining intact for a further 3 or 4 seconds, a bright jet appearing out the back, then it broke into 2 fragments which gradually decreased in brightness. A loud boom was heard about 30 seconds later

Jane Cargill (Jarrow, Tyne & Wear) : Came from north east travelling north west. Very large green oval with bright sparks in the trail.  Went overhead of house – ran through to other side and outside to view, it looked like three parts by then – a middle and two side parts – loads of sparks.

Lee Scott (Blyth, Northumberland) : Heading East to West … at first I thought it was a jet heading towards me. It looked pure bright white in the distance, then as it got closer it turned to a bright orange and appeared to be constantly jettisoning small sections of itself as it passed

Chris Reeve (Kirkcudbright, Dumfries & Galloway) : SPECTACULARLY BRIGHT! – I thought it was a low-flying aircraft at first, like a helicopter with a searchlight. As it approached, first signs of fragmentation and trail appeared around the main head. Lots of very bright colours and detail. Many break off trails all appearing to travel very straight and parallel to one another but rapidly declining and seeming to fall away as it receded

Paul White (Royton, Lancs) : The bright head of the fireball was white with a greenish hue with a long red fragment trail made up of significant number of small particles with larger fragments breaking off occasionally during its course. The tail was at least 20 – 25 % of the distance it travelled at all times until it finally burnt out.

Paul Buglass (4 miles west of York) :  I noticed a very bright light low down over York (due East), to the right, and lower than Arcturus, and very bright with a slight green tint … It seemed to be moving very slowly, flickering slightly, and at first I thought it was a low flying aircraft with its landing lights pointing at us, but they were very bright, too bright for an aircraft  …  as the seconds ticked by it slowly started to show more movement to the left and slightly gain elevation  …  as its angular velocity increased, the bright green light started to show a slight tail as it passed through the bottom of Auriga, and then as its apparent angular speed increased more, a longer trail of darker red/orange trail formed, with bits coming off, as it approached the Plough. 

It then started to lose more distinct fragments downstream, with a orange almost ember like appearance, then the main bright white/green head puffed explosively and lost many more orange fragments which trailed off downstream (very reminiscent of the Peekskill videos) as it passed through the Plough.   This was the highest elevation at about 20 to 25 degrees in the Plough and appeared to be moving horizontally east to west at this point.   The trajectory was very flat, so the flight path had appeared to be pretty horizontal for about 20 or 30 degrees around the Plough and East of the Plough.

It continued West in a very flat trajectory, gradually losing the bright head as it moved to the West, and slowly (very slowly) faded to about 6 or 7 glowing orange points which seemed to linger for at least 15 seconds or more until they very slowly faded from view, still appearing to be heading west, and if anything at a higher elevation than when first observed in the East  …  Total observation time was possibly 60+ seconds from first sighting low in the East to fading from view in the West.

Was it a satellite re-entry ?

Early media reports did suggest that this may have been re-entering satellite debris. However, as the news item posted by Robin Scagell on the SPA web site stated, this was highly unlikely because the fireball was travelling in an approx East to West direction, whereas virtually all satellites travel in a more West to East direction (the rotation of the Earth makes it much easier to launch them in that direction).

Dutch astronomer Marco Langbroek supports this conclusion – his detailed explanation can be found at  sattrackcam.blogspot.nl/2012/09/more-on-21-september-2012-fireball-why.html

Marco also speculates on a possible source for the object that produced the fireball : sattrackcam.blogspot.nl/2012/09/the-21-september-fireball-small-aten.html

Analysis of the exact fireball trajectory, including the possibility that the shallow atmospheric trajectory allowed part of it to exit the atmosphere (and unconfirmed speculation of a link to a similar fireball seen over North America 155 minutes later), is still on-going.

Media Reports

Fortunately, not all media reports focussed on the claims of man-made “space junk”. Some focussed on witness accounts  :

www.itv.com/news/central/2012-09-22/fireballs-light-up-sky-across-midlands/

Others also reflected on how people unsure as to what they are seeing sometimes call the emergency services :

www.bbc.co.uk/news/uk-scotland-19685161

Tony Markham

IMC 2012 Excursion

IMC 2012 Excursion to the Observatorio del Roque de los Muchachos

This excursion took place during the Saturday afternoon and included visits to the CILBO meteor camera, the William Herschel Telescope and the 10.4 meter Gran Telescopio Canarias. The telescopes of the observatory are located high on La Palma (close to 8000 feet above sea level) and thus usually well above the cloud layer.

The CILBO camera system is one of the smallest at the observatory. Along with its partner, located on Tenerife, it is used for meteor triangulation. The aim is to study meteor orbits and also the composition of the particles themselves. At the time of the visit, however, it was out of action due to a fault having caused it to point too close to the Moon. More information about the CILBO cameras can be found at www.rssd.esa.int/index.php

The above image shows the “observatory”. Below we see the camera itself.

The two MAGIC telescopes featured in a recent Horizon programme on BBC2. They study the universe in gamma rays by monitoring the Cherenkov radiation produced when gamma rays interact with particles in the Earth’s atmosphere. This interaction produces a cascade of secondary particles which then emit radiation that can be detected at visual wavelengths.

More information about the MAGIC telescopes can be found at magic.mppmu.mpg.de/

The 4.2 metre William Herschel Telescope has been operating on La Palma since 1987 and continues to be used for a wide variety of astronomical observations in the optical and infrared.

More information about this telescope can be found at www.ing.iac.es/PR/wht_info/

The 10.4 metre Gran Telescopio Canarias has a mirror made up of 36 smaller hexagonal segments and is currently the world’s largest optical-infrared telescope.

More information about the “GranTeCan” can be found at www.iac.es/eno.php

Many more telescopes are located at the observatory, including the Isaac Newton Telescope, the Galileo Telescope and the Liverpool Telescope. The two unusual looking telescope “domes” below are the Swedish Solar Telescope and the Dutch Open (solar) Telescope.

The visit concluded with a trip to the highest point to allow participants to look down into the caldera. Below we see the SPA’s Paul Sutherland returning from one of the viewpoints.

International Meteor Conference : 2012 September 20-23

The 31st International Meteor Conference (IMC) took place on La Palma in the Canary Islands between Thursday Sept 20 and Sunday Sept 23 2012. The 110 attendees were a mix of professional and amateur astronomers, plus a number of journalists invited by the La Palma authorities as part of their plans to promote astro-tourism on the island. Although most attendees were from European countries, some also attended from as far afield as Canada, the USA and Japan.

Being located at around latitude 28.45 degrees north also offered attendees a more southerly view of the sky than most would be used to. This included the Sun rising at a steep angle to the horizon and offering little shade at noon. The night skies saw the star Fomalhaut rising more than 30 degrees above the horizon and allowed view of constellations, such as Grus and Columba, that are not readily visible from the UK.  In addition the star Canopus was visible low in the south as morning twilight encroached.

The Saturday afternoon included an excursion to the Observatorio del Roque de los Muchachos (altitude over 2400 metres) to see some of the telescopes, including the MAGIC telescopes, the William Herschel Telescope, the 10.4 metre Gran Telescopio Canarias and the (much smaller!) CILBO meteor camera. The observatory was reached via a long winding road which ran alongside alongside steep drops which were (only sometimes) “shielded” by crash barriers – La Palma is the “steepest” inhabited island in the world. Photos from this excursion can be found at www.popastro.com/meteor/reports/report.php

The meeting itself was held in the resort of Los Concajos on the east coast of the island. As at recent IMCs, most speakers were restricted to only 15 minutes so as to allow as many speakers as possible. Here is a summary of some of the presentations:

Sirko Molau (Germany) gave an overview of the 2011 results from a network of 80 cameras in 16 different countries, which has recorded over 300000 meteors.  Attempts are being made to go beyond merely identifying meteor showers and meteoroid orbits and moving on to automatically determining limiting magnitudes and effective atmospheric collection areas. He also outlined the problems involved in correcting for radiant altitudes in ZHR calculations – the more “simple” formulas can often lead to spurious peaks in analyses. He showed how adjusting the formula can give better correction for low radiant altitudes.

Filip Novoselnik and Denis Vida (Croatia) described the possible detection of a new meteor shower in Croatian Meteor Network and SonataCo data. The shower may be an extension of the southern Delta Aquarids.

Felix Bettonvil (Netherlands) outlined early work involved in setting up an automated all sky camera system and highlighted the need to keep out dust and to control the humidity. Noise levels become high when the temperature increases – the internal temperature has on occasions reached 47C

Pete Gural (USA) gave an update on the CAMS system. This is funded by NASA and is based on having lots of cameras at a small number of stations and can record meteors down to mag +4. This has allowed 47000 meteoroid orbits to be defined in one year, with 31 new meteor showers being added to the IAU database.  Future plans included capturing spectra of bright meteors. For more information, see  http://cams.seti.org

Johan Kero (Sweden) described work carried out to detect meteor head echoes using the MU radar. Despite issues from operating in an auroral zone, this recorded 106139 meteors during 2009-10, with the highest velocities being, as expected, from meteors radiating from the apex direction. Future work will involve the EISCAT_3D system – see www.eiscat3d.se

Herve Lamy (Belgium) gave an update on the BRAMS network. This currently has 23 observing stations and uses its own radio beacon. Attempts are made to identify meteors seen from more than one station in order to determine trajectories – although this proved difficult during the 2011 Draconid outburst.  For more info, see http://brams.aeronomy.be

Sylvain Ranvier (Belgium) described work carried out during the 2012 Perseids  to measure radio polarisation.  158 echoes were detected, most of which were strongly polarised. The work has the potential to give insight into the physical phenomena that produce meteor echoes and into (epsilon) multiple branch echoes.

Jean-Louis Rault (France) gave an update on issues affecting radio meteor observations. The switchover of TV stations from analogue to digital is an increasing issue. Groups can set up their own beacons, but these will be low power and so observers have to be within a few hundred kilometres of the beacon. Other potential options include radar systems being set up by ESA and NORAD and also aviation radars.

Megan Argo (UK) gave a short talk about the work of Sir Bernard Lovell who died recently. She described how he had expected his early investigations at Jodrell Bank to reveal cosmic rays to be the cause of certain radar echoes, but instead found that ionised meteor trails were responsible. The 1946 Draconid storm was subsequently monitored at radio wavelengths. The presentation concluded with a short video in which Lovell described this early work.

Regina Rudawska (France) described the 2011 Draconids airborne campaign – the first such mission operated from Europe. This used two aircraft (SAFIRE and EUFAR/DLR) and had to address issues with agreeing flight plans with several countries, including Russia, plus issues regarding the auto-detection of meteors from a moving plane. The first Draconid peak is probably weakly present in the data, but the second peak was clearly detected at the expected time.

Jiri Borovicka (Czech Rep) outlined the results of a 2011 expedition to northern Italy which succeeded in recording the spectra of 8 Draconids. These showed the meteoroids to have normal cosmic ratios for Mg, Na and Fe, to have a 90% porosity  and were consistent with grains having a typical size of 50-120 microns

Damir Segon (Croatia) reported the results of the Croatian Meteor Network for the 2011 Draconids. Orbits were determined for 88 Draconids (25 being detected from 3 or more stations). However, the calculated aphelion distance for the orbits was very dependent on the deceleration model used, ranging from 4.9au to 6.0au

Stijn Calders (Belgium) described software that can be used to predict where in the sky a specular radio reflection was likely to occur for a particular meteor shower radiant location. This location inevitably moves as the radiant crosses the sky and can correspond to an area over 100km across.

Galina Ryabova (Russia) reviewed the possibility of the Earth encountering meteoroids ejected when 3200 Phaethon (the Geminid parent) brightened by over 2 magnitudes for 2 days in June 2009. The best chance will be when Phaethon approaches to 0.0689au of the Earth in 2017. The conclusion was that activity is possible, but the probability is not high.

Regina Rudawska (France) outlined the possibility of seeing meteors from asteroid 2012FZ23, an Apollo asteroid with a high inclination. The possible radiant would lie in the southern constellation of Chamaeleon.

Maria Hajdukova (Slovakia) reviewed the data for hyperbolic meteoroids. These have sometimes been suggested to be interstellar in origin.  Alternatively, the hyperbolic classification might be the result of measurement errors or the meteoroids might only have become hyperbolic as a result of interactions within the solar system. The results of her investigations suggest that only 2-4% of “hyperbolic” meteors are really interstellar in origin.

Nagatoshi Nogami (Japan) gave an overview of the 50 meteorites that are known to have fallen in Japan.  The oldest, the Noogata meteorite, dates from 861 May 9 and was for a long time stored in a shrine. Another, the Shirahagi meteorite was found in 1890 (date of fall unknown) and was for many years used for weighing a pickles cask. Later, part of it was used to make a 60cm sword.  More recently, on 1992 Dec 20, the Mihogaseki meteorite broke a house roof and passed through two of its floors.

Damir Segon (Croatia) described work to detect meteors in the near infrared. The camera used had 60-70% sensitivity to the 777nm oxygen line and used a filter to cut out visual wavelengths. Some of the meteors detected show similar light curves in the visual and infrared whereas others are very different.

Thomas Weiland (Austria) gave an overview of work to monitor the Eta Aquarids from La Palma in 2011. Over 7 nights, during which the LM ranged from 6.3 to 6.9, two observers recorded 354 Eta Aquarids, including two Earth grazers, but few fireballs were seen. The peak ZHR was around 55 during May 6-7.

Geert Barentsen (UK) reviewed the issue of how to determine the flux of large meteoroids. The US Military have data which indicate 300 large bolides were detected during 1994-2002, but this data is restricted. He suggested that monitoring Twitter for bursts of tweets mentioning words such as “fireball” or “meteor” can give an indication as to when major fireballs are seen (the Sep 21 UK fireball which had appeared the previous evening produced one such burst of tweets).

Guliyev Ayyub (Azerbaijan) summarised the various groups of sun-grazing comets and reviewed the likely meteor streams that may be associated with these. Unfortunately none of these seem to currently pass close to the Earth.

Danielle Roser (USA) described the results of attempts to simultaneously observe the 2012 Lyrids from three different locations: from the ISS by astronaut Don Pettit (altitude around 400km), from a balloon (altitude 35km) and from the ground. 155 meteors (16 double station) were seen from the ground, but only 2 of these were possible recorded from the ISS. The balloon’s useful recording time was 1.6 hours during which 31 meteors were recorded, but none of these were recorded by the other two methods.

Ovidiu Vaduvescu (Romania) described the EuroNEAR collaboration. In the absence of a dedicated European telescope for NEA detection, this involves scanning plate archives for possible images in order to find pre-discovery images.

The 2013 International Meteor Conference is due to take place in Poznan, Poland from Thursday August 22 to Sunday August 25.