A rare red rainbow was photographed in County Antrim on Friday morning. Pete Kirk observed and photographed the phenomenon in Mallusk.

Rainbows form when sunlight is bent and reflected by water droplets in the air, splitting the light into different colours. Red rainbows form in the same way, but they appear at sunrise or sunset when the sun is low in the sky.

At these times, sunlight travels through more of the atmosphere. Colours such as blue and green are scattered away, leaving mostly reds and yellows. This gives the rainbow a reddish glow.

The process is essentially the same phenomenon that causes red sunsets.

Unlike a red sunset, red rainbows are uncommon. People who study the skies may only ever be lucky enough to see a red rainbow once or twice in their lifetime.