A great fireball of magnitude -9 appeared above the center of France on July 26th, 2020, at 23h12m UT. It has been seen from all over France and neighboring countries and sonic booms were heard from around Paris.
The night of 26–27 July 2020, I decided to observe comet C/2020 F3 Neowise. It was the last day to see it without moonlight. I had the chance to be in a holiday place in Cerilly, Auvergne, France, with a nice dark sky.
At 23h12m UT, 30 minutes after the moonset, I was making pictures of comet Neowise with Ursa Major when I saw a bright fireball beginning to appear from near my zenith and descending during 10 seconds to the horizon displaying an intense bright green light! It ended disintegrating into small pieces. It was the most beautiful fireball I’ve seen in real life!
Luckily, the fireball crossed the field of my camera.
The fireball has also been observed from all over France and even from Belgium, Germany, Switzerland, the Netherlands, as reported by nearly 150 people on the IMO website.
Sounds like rumble, detonations and booms was reported by about thirty witnesses around Paris.
Julien A. at Athis-Mons (fr) reported : « about 1 or two minutes after low pitched attenuated rolling boum during 2 sec »
Nicolas B. at Sainville, Centre-Val de Loire (fr) said : « double detonation at 1h16min00 + -3s exactly, not necessarily linked?»
2 Observational data
The fireball occurred on 2020 July 26 at 23h12m23s UT and has been caught by many cameras in France: 12 of the FRIPON network, 4 of the BOAM network and furthermore by some individual amateurs.
According to the data from the FRIPON network, the fireball reached its maximum brightness of magnitude –9 at an altitude of 55 km.
The fireball crossed the whole field of view of the Rasberry Meteor System camera, FR000A, located at Cérilly, Auvergne, France. It is the longest trajectory recorded by a camera during 9.30 seconds.
Three other cameras of BOAM network caught the event: two all sky cameras and a 60° FoV camera.
An independent amateur station based in Reuil-Malmaison, Paris region, was particularly well placed, on the trajectory of the fireball. A first south-facing camera recorded the meteoroid coming in and starting to split into several pieces and a second facing northwards shows the object breaking up at the end of its light path.
see also the second video in comment
Unfortunately, the astrometry has not been calculated and it is not possible to compute a trajectory from these two captures. But a study of the images allows to see the dynamics of the fireball in the atmosphere.
Time synchronization of the cameras is done with Meinberg on a ntp-server and the meteor dynamic as time match to that one on the LITIK1 video.
At 23h12m22.28s, the fireball starts, very faint, on the video of the southward pointed camera. At 23h12m24.80s, a second track (b) appears, following the more important one (a) until 23h12m28.88s.
A series of small explosions take place on the main piece (a) at 27.52s, 27.64s, 27.80s and 27.88s giving rise to a few small bright pieces disintegrating quickly, visible in the capture at 28.00s.
At 23h12m28.24s, the fireball suddenly strongly brightens, certainly corresponding to the shattering of the main object (a) and the creation of a third important piece (c). Piece (c) is clearly visible on the captures at 28.88s and 29.04s and leaving the FoV of the southwards pointed camera at 29.20s.
On the northwards pointed camera, the fireball appeared at 23h12m31.62s. According to the synchronization of both cameras, 2.4s of the path is missing and only one of the fragmented objects reappeared. From 32.904s and until the very end of the luminous trajectory at 33.86s, the object seems to break up into three pieces. It started at 23h12m22.28s on southwards pointed camera and ended at 23h12m33.86s on northwards pointed camera, corresponding to a duration of 11.58s.
Last very interesting capture, come from an amateur astronomer, Romain Buté, who observed and shoot the neowise comet, near Montbellet, France and report his observation on the IMO fireball report page. He was lucky to shoot the fireball with his DSLR camera in narrow field of view 12×18° and with a “dji osmo” action camera on timelapse shooting mode and 145° of field of view.
|Observer||Long. (°)||Lat. (°)||Alt. (m)||Dur. (s)||Ra. 1 (°)||Dec. 1 (°)||Az. 1 (°)||Ev. 1 (°)||Ra.2 (°)||Dec 2 (°)||Az 2 (°)||Ev 2 (°)|
Table 1 : Data for T. Gulon and R. Buté extracted with astronomy.net and FR000A, LITIK2 and CHI37 data from UFOsuite.
The multiple station data of the BOAM network and DSLR pictures of amateur astronomers allowed to calculate the trajectory and orbit.
|trajectory||dur. (s)||long. b (°)||lat. b (°)||Hb (km)||long. e (°)||lat. e (°)||He (km)||dist (km)||incl. (°)||vo (m/s)||vg (m/s)|
|orbit||a (A.U.)||q (A.U.)||e||ω (°)||Ω (°)||i (°)||αg (°)||δg (°)|
Table 2 and 3 : Trajectories and orbital elements – BOAM computation UFOorbit – DSLR cam computation author’s table
3 Electrophonic, photophonic sound or auditive hallucination?
At the same time of the appearance of the meteor, I heard like a “sound of blowing” or a thin “fff” made with the mouth during 2 to 3 seconds in the first part of path when the object was high in the sky.
A few persons describe the same phenomenon as Anthony J. at Dijon who heard the same sound : «Like when you immerse a very hot object in cold water and tamp out»
Jason C. at Saint-Germain-en-Laye, have heard as : «A very light breath like something burning until the fireball crumbles.»
Gregory P., amateur observer at Vitry-aux-Loges, report : «I don’t know at all how to explain it as a kind of sound in the sky as its entery. A sort of hissing.»
Normally, it is impossible to hear the fireball at the same time of appearance, because the object is far away from the observer, some 50 to 100 km or more and the sound takes several minutes to arrive. But this phenomenon had already been reported several times during a fireball event.
From the 1980s years, according to accepted knowledge, hearing sound simultaneously during the appearance of the meteor could be explained by electrophonic noise. Indeed, the disintegration of a meteor into the atmosphere generate huge energy and creates ionization of the air. This plasma produces low frequency radio emission (ELF/VLF) travelling at the speed of light and that could be transferred into acoustic waves whenever appropriated objects such as fences, hair, vegetation, glasses are in the vicinity of the observer.
In 2017, in the journal “scientific report” (https://www.nature.com/articles/srep41251), Spalding et al. propose a new way to explain this “anomalous” sounds. Intense light from a fireball could rapidly warm common dielectric materials closed nearby the observers and then produce some small oscillation in the air and create sound wave. The process is called photo-acoustic coupling.
And why not an auditory hallucination? It would be interesting that specialists in psychology or neuroscience investigate this possibility. Today, this is not fully explained, studies must continue.
The author wishes to thank Dominique André and Romaric Buté for their cooperation and their permission to include their images and BOAM members and team for providing their camera data and detection.