Footage has been recorded of a large meteor in the sky over north-east Scotland.
Police received a number of calls after a big, bright flash or 'fireball' was seen - with people reporting seeing a blue, white or green light.
Others said they had heard a rumbling sound.
Professor Keith Horne, from St Andrews University, said the meteor was probably about 10cm across, with the rumbling sound caused by a sonic boom.
The light appears to have been seen as far south as Berwickshire in the Scottish Borders and Newcastle at about 18:45 on Monday.
Garry J Hunter contacted BBC Scotland to say he had seen the flash over Lumphanan in Aberdeenshire. He described it as "a huge fireball-like trail across the sky, which seemed to then explode and light up the whole sky".
The Met Office said the event was "not weather-related" as there were no thunder storms recorded on Monday night.
Professor Horne, who is from the university's School of Physics and Astronomy, said the flash would have been caused by a meteor travelling at about 30km per second.
"What you've seen is a piece of rock from outer space that has crashed into the earth," he said.
"When it hits the atmosphere it starts to burn up... It releases all this energy into the atmosphere which will cause a bright flash and sometimes bits of this explode."
The professor told BBC Radio Scotland's John Beattie programme that most meteors were just a speck of dust - causing commonly seen "shooting stars" - but this one would have been about 10cm (4in) across.
He said it probably burnt up at an altitude of 20 miles (32km) without any pieces reaching Earth.
Driving instructor Bill Addison, from Buckie in Moray, recorded the sight on his dashboard camera.
Mike Fleming captured similar footage on the road between Dunecht and Castle Fraser in Aberdeenshire.
'Scary and amazing'
The "flash" was also caught on a security camera at Woodend, Lumphanan, Aberdeenshire, which was sent in by Craig Lindsay.
Jenni Morrison captured dashcam footage of the flash as she drove on the A944 between Westhill in Aberdeenshire at about 18:45.
She said: "it was the most surreal thing I have ever experienced".
She told BBC Radio Scotland's Good Morning Scotland programme: "It was pitch black and then all of a sudden it was like a light switch went on. It became daylight - the whole sky lit up.
"I looked at my son, he looked at me and then it just went black again. It really didn't last long at all - literally seconds.
"We didn't realise what it was at the time until we looked back on my dashcam. We saw the ball of light over the trees on the left side coming down at some speed and then a massive flash.
"It was scary and amazing at the same time."
Val Hamilton from Nethy Bridge said she saw the sky light up south west of Aviemore at about 18:45.
"I saw a white ball with a tail passing through the sky at great speed. It was very dramatic," she said.
Heather Mullan, from Aberdeenshire, said: "The sky seemed to slowly brighten then there was a double flash of intense light then nothing.
"About 90 seconds later there was a double muffled sound like a sonic boom. We assumed we had just witnessed a meteor although no meteor showers are due. It was spectacular."
The Reverend Helen Savage told BBC Scotland: "I was driving across the Durham Moors from Rookhope to Hunstanworth at that time and was surprised to see what I thought to be lightning - to the north.
"When I got home 20 minutes later I checked Rainfall radar - I didn't think thunder storms had been forecast - and found nothing recorded."
Phil Hoyle was leaving the Balmedie Country Park, near Aberdeen, when he heard a "humming noise" over the sea.
He said: "When I looked I could see this light moving quickly with a small white tail, but it stopped over the sea and had a shape to it."
Julian Bell, from Dollar, in Clackmannanshire was driving over the Clackmannan bridge.
He said: "I thought at first it was a firework but it was too bright and white and instant and covered too much area for a firework.
"I then thought it was thunder and lightning but didn't hear anything and there was only one flash and no rain."
Ross Stewart told BBC Scotland he was returning from offshore and was on a helicopter back to Aberdeen at the time.
He said: "I noticed a few small clouds that seemed to be glowing slightly, then the whole sky above the chopper lit up followed by a series of flashes. I thought we were going to be hit by lightning."