A colourful new celestial phenomenon has been spotted in skies over Scotland.
Known as Steve, the spectacle was initially discovered by a group of citizen scientists in Canada in 2016.
But keen-eyed stargazers in the Highlands and Islands spotted the mysterious spectacle during displays of the better known northern lights, or aurora borealis, in recent days.
The new natural wonder, another kind of aurora, consists of long spurts of mainly purple and green light that appear in a glowing ribbon stretching from east to west across the night sky.
Although the name Steve was initially a joke, members of Alberta Aurora Chasers who first documented the phenomenon later said the moniker was an acronym for strong thermal emission velocity enhancement.
Steve was recently seen from the isles of Skye and Lewis. On the mainland, viewers near Oban in Argyll, Knoydart in Lochaber and Gairloch in Wester Ross were also rewarded with a showing.
Some of those lucky enough to witness the unusual event posted spectacular pictures on social media.
The northern lights appeared more widely, with sightings in Shetland, Caithness and Aberdeenshire.
Nasa has launched a study into the newly identified illuminations, asking for members of the public to send in reports and photographs of any sightings in the northern hemisphere.
They say a lot can be revealed about the interactions taking place from the colours and patterns that show up.
“This is a light display that we can observe over thousands of kilometres from the ground,” said Nasa’s Liz MacDonald, who is the leading the project.
“It corresponds to something happening way out in space.
“Gathering more data points on Steve will help us understand more about its behaviour and its influence on space weather.”
Auroras are caused by highly energised particles called the solar wind, which are fired out from the sun into space.
They interact with earth’s powerful magnetic field, creating a dazzling display of light.
Steve can be spotted further south than the aurora borealis, and is thought to be an “optical manifestation” of another phenomenon – the sub-auroral ion drift, or Said.
Scientists have been studying Saids since the 1970s but until recently had not known there was an accompanying visual effect.