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Notable Meteors & Fireballs : 2017 November

Here, in reverse chronological order, are details of notable meteors and fireballs reported to the section during November 2017:

2017 Nov 29th  17:06:42 UT

This fireball in the evening twilight was widely seen.

The image shown here was captured by William Stewart (Ravensmoor, Cheshire) of the NEMETODE network ( http://www.nemetode.org )

Visual reports include the one from Mell Jeffrey (Norton, North Yorkshire). Mell was driving at the time and comments that she initially thought it was just car headlights reflecting off her windscreen, before realising that a reflection from headlights wouldn't have reflected and moved in such a way. She records the event as starting in her western sky, descending steeply towards the WNW and having a duration of 3-4 seconds.

Many reports of the event were made via Twitter. These reports were inevitably rather brief (e.g. "Did anyone else just see a fireball like a massive shooting star pass across the sky over England?" and "Spotted it in Bolton - spectacular!", but did give an indication as to which parts of the UK the fireball was seen from - tweets came from locations as far apart as Edinburgh and Essex. Some also illustrate how members of the public react to such events, with comments including "it was incredible to see it, quite spooky" , "I went inside and told my wife, but she looked at me funny" and "I wish some boffin has a photo of it".

Although the fireball was "detected" by several automated video systems, the number of good images captured proved small. Richard Fleet (Wilcot, Hants) recorded a flash through the clouds via his NW facing video camera at the time of the fireball, while Alex Pratt (Leeds) reported that his NW facing video camera was automatically activated to record a video clip at this time by a flash outside of its field of view.

William Stewart (Ravensmoor, Cheshire) did record the fireball via his all sky camera, as it passed through patchy cloud, with the software he was running classifying it as a member of the December Alpha Draconid minor meteor shower and possibly around magnitude -7.  His image is shown above.

William reported the fireball via  this tweet , which includes a link to his video of the fireball

Details of all of the reports of this fireball submitted to the IMO can be viewed via this link http://spa.imo.net/imo_view/event/2017/4781

The provisional analysis of the visual reports submitted to the IMO suggested that the fireball was heading in a NW to SE direction and had a ground track over western Cheshire.

William, however, was able to carry out a more detailed analysis, based on the more precise sky positions and speeds provided by his video record and by a second video captured by another NEMETODE member, Nick James (Chelmsford). 

This analysis places the ground track slightly further west and over north east Wales. It indicates that the fireball became visible at an altitude of about 95km and ended at an altitude of around 28km.

2017 Nov 29th  02:51 UT

Bill Ward (Kilwinning) reports capturing 325 images during the night of Nov 28-29, although on closer inspection he found that 82 were due to cosmic rays rather than meteors.

His best capture was of an event at 02:51:59 UT for which he captured the second order spectrum shown here.

Bill captured the spectrum using his 600 lines/mm system and notes that he was very close to resolving the magnesium triplet around 5175A.

Bill also comments that the spectrum also showed emission lines from Iron well into the near UV.

 

 

2017 Nov 25th  07:13UT

The night of Nov 24-25 proved productive for Richard Fleet (Wilcot, Hants).

In addition to the fireball just before midnight, he imaged another fireball in the morning twilight, just before his automated imaging system was due to switch off.

The slow moving fireball was imaged via his SW facing video camera, from which the accompanying still image is taken.

The video can be viewed  here

The fireball was also seen visually by Rob Sime (Rugby), who saw the fireball low in his SSW sky and described the fireball as breaking up into approx 10 pieces and showing green and white colours.

The IMO also received many visual reports of this fireball from witnesses across the southern half of the UK and from NW France.

The reports submitted to the IMO can be viewed here

This map in this link also shows that the most likely ground track for this fireball was in a WSW direction just south of the Dorset coast.

2017 Nov 24th  23:59 UT

This spectacular fireball was seen visually by Adrian Avery (West Sussex) and imaged by Richard Fleet (Wilcot, Hants).

Adrian saw the fireball in his western sky, describing it as "Brilliant Green, appeared to explode (soundlessly) before vanishing".

Richard imaged it via his SW facing video camera, from which the accompanying still image is taken. The video can be viewed  here

The fireball was seen by large numbers of observers across the south of England, observers further north presumably missing out due to cloudy skies.

The reports submitted to the IMO can be viewed  here. This summary also marks the most likely ground track for the fireball and suggests that despite Richard's initial guess that the fireball may have been over the English channel, it may actually have been a little further north and located over southern Hampshire.

2017 Nov 19th  19:55:08 UT

Richard Fleet (Wilcot, Hants) has posted this fireball image that he captured through thin cloud via his SE facing camera.

The fireball was also imaged by another camera of the UKMON network, based at Ash Vale in Surrey.

Intriguingly, a video has also been posted via Twitter by airlivenet of a fireball imaged from Heathrow airport at 20:09 UT.  This video bears a timestamp approx 14 minutes later than Richard's image, but the fireball appears so similar in appearance as to raise the possibility that it shows the same object and that the time discrepancy is due to an error on the video system's clock.

The video can be viewed via  this link

However, there are also several reports to the IMO of a fireball at around 20:10 from four witnesses in the UK and many more in France.  These reports can be viewed here .  The preliminary IMO analysis indicates that this latter fireball's trajectory was in a westerly direction over northern France.

2017 Nov 19th  05:47:05 UT

William Stewart (Ravensmoor, Cheshire) captured an image of this Leonid fireball via his SE facing camera. The software recorded its magnitude as about -6, although there is some uncertainty in this due to the presence of thin cloud.

William also reported capturing a spectrum of the fireball and detecting the forward scatter radio reflection from its ionisation trail. Michael O'Connell, another member of the NEMETODE group, also reported detecting the radio reflection from Ireland. Three other NEMETODE members subsequently reported having captured images of this fireball, allowing its atmospheric trajectory to be determined. For further details, see here

2017 Nov 19th  02:29:06 UT

Paul Sutherland (Walmer, Kent) captured this DSLR image of a Leonid fireball as it crossed the constellation of Coma Berenices. 

Paul did not see the fireball directly, but the fireball was also recorded by several observers in the Netherlands (see  here ) and these reports indicate that it was probably around magnitude -8.

Paul also captured a number of images (included in the 2017 Leonids report  )  showing the decay of the fireball's persistent train, which took more than 10 minutes.

 

2017 Nov 17th  00:43:42 UT

Bill Ward (Kilwinning, near Glasgow) captured an interesting spectrum of a bright meteor on the morning of Nov 17th. Although this was close to Leonid maximum, Bill originally classified it as a sporadic but, following a more detailed analysis of its path, subsequently re-classified it as a Leonid.

The image shows the first order spectrum -  the meteor itself lies outside of the field of view but will have been travelling from left to right and hence the spectrum is fairly vertical. The two brighter spectral lines towards the mid right hand edge of the image are the usual emission lines from magnesium and sodium.

The two brighter "bands" towards the right hand side of the image are due to flares near the end of the meteor's path.

Although all spectral lines brighten at the position of these flares, Bill notes that three of the fainter lines brighten by a much greater amount than to the other fainter lines.

Bill has identified these three lines as being related to ionisation - and has labelled these lines in the intensity plot.

As can be seen in the plot, these ionised lines are barely detectable in the (lower) plot measured midway along the path of the meteor but are very obvious in the (upper) plot measured at the time of the flare.

Bill notes that this was clearly a fast moving meteor, given that the 557.7nm "forbidden" line of oxygen is briefly visible at the start of the spectrum, this being a spectral line resulting from emission that can only occur at altitudes higher than 110 km. This high speed also fits in with it being a Leonid, the Leonids producing particularly fast meteors.

 

2017 Nov 13th  04:31:59 UT

Bill Ward (Kilwinning) captured this image of a Leonid fireball on the morning of November 13th. The image shows it moving away from the 'sickle' of Leo.

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.

 

 

 

 

2017 Nov 12th  18:29 UT

Richard Fleet (Wilcot, Hants) has posted this image of a bright sporadic meteor that he captured via his south east facing video camera during the early evening of Nov 12th.

 

 

 

 

 

2017 Nov 7-8

Bill Ward reports capturing spectra of three meteors during this night, each showing its particular characteristics. The colourised  synthetic spectra are shown below:

Bill also reports that he has been investigating the feasibility of using liquid crystal "rotating shutters" with his DSLR cameras in order to determione the speeds of imaged objects (and help differentiate between meteors and satellites).

You can read about his results at https://britastro.org/node/11675

Added by:  Tracie Heywood