Hikers spot rare 'Fogbow' in Yorkshire - but what is it?

A couple out hiking in the North Yorkshire moors on Thursday were surprised when they spotted what looked like a white rainbow.

The peculiar white ring appeared to the hikers in the North York Moors National Park as they came out of fog with the sun directly behind them, one of the walkers said on social media.

The picture appears to be a rare weather phenomenon known as a 'fogbow'.

The Met office says a fogbow is similar to a rainbow, but is formed out of water droplets in fog, mist or cloud, instead of rain.

The water droplets in fog are much, much smaller than rain droplets - nearly always less than 0.1mm in diameter - and undergo different physical processes than their raindrop cousins.

The tiny fog droplets still reflects sunlight from the water droplet back to the observer, like in a rainbow, but the light is diffracted.

This process smears out the colours and lends the phenomenon the name of 'white rainbows', although sometimes a tiny bit of colour can be spotted.

The fogbows look similar to rainbows but devoid of colour. Credit: @SwaledaleBirds

The Met offices says for a fogbow to take place the fog must already be "relatively diffused and thin" to allow the light to pass through and create the effect.