At first glance at these photos, you'd be forgiven for mistaking them as snaps of the Northern Lights.

But the strange ribbons of purple light are actually a phenomenon known as ‘Steve’, which has baffled scientists since it was first spotted in 2015.

The purple lights are often accompanied by smudges of green lines, nicknamed ‘picket-fences.’

Now, scientists from the European Space Agency (ESA) have studied photos of this remarkable phenomenon to understand what it is, and how it forms.

The team analysed photos of Steve from two different locations - western Alberta and eastern British Columbia - and used the stars in the background to precisely orient the lights.

The purple lights are often accompanied by smudges of green lines, nicknamed ‘picket-fences’

They estimate that the optical emissions of Steve range from 130 to 270 km in altitude, while the green picket fence ranges from 95 to 150 km in altitude.

William Archer, from the University of Calgary , said: “It is remarkable to see that originally citizen scientists of the Alberta Aurora Chasers triggered the curiosity of scientists to study Steve.

“I’m excited that were able to extend our understanding of Steve using photographs taken by citizen scientists.”

Unlike normal auroras, which occur in an oval shape and last for hours, Steve is a picket-fence structure that lasts for just 20 minutes to an hour

While Steve may look similar to the Northern Lights, the two phenomena are actually very different.

The Northern Lights are caused by energetic electrons colliding with the atmosphere roughly 100km above Earth’s surface.

In contrast, Steve does not appear to be caused by electrons and instead researchers believe that Steve is caused by a 25km-wide ribbon of hot gasses at an altitude of 300km, with a huge temperature of 3,000°C.

Read More

Astronomical Events

ESA’s Roger Haagmans said: “Although this is a conceptually straightforward result, it contributes significantly to our understanding of Steve.

"The combination of Swarm data along with photographic observations may help enable us to unravel the mystery that is Steve.”

The name ‘Steve’ was chosen from a scene from the animated movie Over the Hedge, where characters choose a name for something unknown to them.