Cette page en français
See here for reporting information.
| Number: | FR0148 |
|---|---|
| Date written: | November 6, 2006 |
| Date received: | November 6, 2006 |
| Date published: | November 11, 2006 |
| Date of sighting: | November 5, 2006 |
| Place of sighting: | France, Santec |
| Original language of report: | French |
| Reported using: | |
| Unreleased information: | Name, firstname, email address |
| Investigation, additional information: | None |
| Explanation: | Plane degassing contrail, explained to witness |
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Subject: unidentified object Roscoff In Santec near Roscoff, Sunday after midday November 5 (4 P.M. approximately), we saw in the sky, a very pure sky without cloud, a very luminous motionless object of which I send the photograph to you. It should be enlarged for better seeing. Maybe you can give me an explanation. Thank you. [Email] |
The attached original digital photograph is a 1.6 MB file. The version shown here was reduced by my care for acceptable download time of the page and the insert added to show what was intriguing, in the size it has on the original photograph.
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A plane flying at high altitude can create exactly this type of trail in several circumstances:
The sunlight arriving from below colors the trail in orange whereas it would be white if the sun was higher (the sky would then be blue).
The plane probably degasses its wings tanks, or has jet engines on the wings, hence two trails with a separation corresponding to the wake caused by the fuselage in the middle.
The trail can be an ordinary trail caused by water vapour condensation as ice crystal particles at the passin of the jet engines, with a short trail if it starts at the time when the plane enters in a pocket sky charged in vapour in a a generally dry sky. But most of the time, the low length of the trail is rather indicating of a fuel degassing: fuel is ejected from the wings tanks. Besides fuel, a plane can eject cooling liquids or have used its fire extinguishers, it also emits sulphered aerosols and soots.
The fact that the plane is not visible can have two explanations: it can be because of its size relatively very small compared to that of the trails. Contrails and degasssing can lead to trails spread out over hundreds of meters in width and much more in length. Added to the well-known phenomenon of "contrail without plane" caused by a lack of color difference between the plane and the sky that it reflects on its mettlic reflective underside surface, the plane is just "invisible". The other possibility is that the plane moved away long ago and simply left the trail there behind.
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Left: Example of what is going, seen from closer. |
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Left: Massive degassing of a jet in the setting sun, photographed in October 2003 in Wales, then published on the "Astronomy Picture of the Day" (APOD) website, which had "mystified NASA scientists" who thought that it was that it was a photograph of an "extraordinary meteor". Finally, the corrected explanation was admitted: a jet degassing fuel. |
