Stargazers in England have been treated to a spectacular light show, with the northern lights stretching across the UK in a rare display.

While it’s not uncommon to see the northern lights, otherwise known as aurora borealis,  in Scotland and northern parts of the UK, strong solar activity and clear skies meant that people in areas as far south as Kent and Cornwall also got to enjoy the show.

High visibility led to many photos of the phenomenon’s brilliant, multi-coloured lights.

What causes the northern lights?

According to The Met Office, the UK’s official weather agency, the northern lights are a consequence of charged particles in active solar wind colliding with molecules in Earth’s upper atmosphere.

The Sun emits solar winds that stream away from it at about 1.6 million kilometres per hour.

When the magnetic polarity of these winds are the opposite of Earth’s magnetic field, the two combine to allow energy particles to flow into the Earth’s north and south poles.

While the lights usually stick to a ring about 2,650 kilometres across the Earth’s poles called the annulus, massive plasma bubbles ejected from the Sun – also known as coronal mass ejections – can cause the annulus to expand and reach further from the poles.

Why are the northern lights different colours?

The northern lights can present in different shades of blue, green, red and purple, and it all has to do with which gas molecules are hit at what point in the atmosphere, according to The Met Office.

This is because different amounts of energy are released at different wavelengths of light.

Oxygen gives off green light when hit at around 100km above Earth, while at 160km to 320km above the planet, it produces rare, all-red lights.

Close to Earth, nitrogen will cause a blue glow in the sky, and purple is produced when it’s hit higher in the atmosphere.

Will we see northern lights in Australia?