What was that in the sky just before midnight?

[Debbiee]

Sorry if I am posting in the wrong place but I saw something very unfamiliar in the sky last night and wondered if anyone can explain it.

Just before midnight the moon was high in the sky and really bright and just to the left of it a thick white line stretched vertically downwards almost to the horizon.  It too was pretty bright but not as bright as the moon.  I thought initially it might be a kleig light, then maybe a plane headlight (I’m near Heathrow), then maybe a planes dust trail illuminated by the moon. 

The line remained straight but in about 10 mins moved quite quickly away, moving from the vertical to diagonal and fading in the distance.  My attempts to photograph it with my phone were not great, taken after it had faded a lot and show just a thin line.  All suggestions gratefully received.

Edited December 1, 2020 by Debbiee
add Poor photo taken with phone

[Tiny Clanger]

I saw a 'planes contrail streaming right across the sky more or less horizontally expand and disperse incredibly slowly over the course of a couple of hours (it still hung there at 2am when I gave up and bought my telescope in) The light from the nearly full Moon above it lit the water droplets (actually more likely to have been ice crystals up there last night) beautifully, making it really stand out, and the length of time it sat there without being broken up showed how still the atmosphere was.

Might something similar be what you saw ? You're bound to have more flights and therefore contrails nearby than I do !

[Debbiee]

Thanks for replying Tiny Clanger.  That sounds like it could well have been it then.  Usually the trails I see gradually become wonky as they disperse, so I dismissed the idea.  Amazing, I have lived here for almost 20 years and never seen anything like it before.  As you say the atmosphere must be unusually slow.  I will be out looking tomorrow.  Wish I had a telescope!

another thought though, usually planes contrails stay in pretty much the same place in relation to the ground, but this was moving away from me at some speed, and from a big line to invisible in the distance could not have been more than 20 mins.

Edited December 1, 2020 by Debbiee

[Peter Drew]

Definitely a contrail, often a good indication of air stability as you suggested.  Aircraft in and out of airports don't leave contrails, they're nowhere near high enough.    🙂