Moon halo over Budapest, Hungary
© EPA
The halo phenomenon is seen around the Moon above Budapest.
It's been quite a week for stargazers across the globe after a rare lunar eclipse had a spectacular impact on the moon. A super blood wolf moon moved into the UK on Sunday night, during which sunlight passing through Earth's atmosphere lit the celestial body in a dramatic fashion, turning it red. Now the moon has experienced another atmospheric phenomenon, with pictures showing its light creating a halo above Earth.

Stunning pictures taken of the sky above Budapest, Hungary, show the halo moon lighting up the sky with a never-ending rainbow. What is a halo moon? Scientists call the phenomenon a 22° halos because the ring has a radius of approximately 22 degrees around the sun or moon. The halos are caused by clouds high up in the sky - 20,000 feet or more above our heads - that contain millions of tiny crystals. As the light hits the ice crystals and reflects, the halo is created. It is also caused by refraction - the splitting of light as the sun or moon shines through the thin clouds - or a combination of both effects.

Moon halo over Budapest, Hungary
© EPA
Is there normally colour?

Because moonlight isn't very bright, lunar halos are mostly colorless, but you might notice more red on the inside and more blue on the outside of the halo. These colors are more noticeable in halos around the sun but it is noticeable in the pictures from Budapest. Usually, the inner edge of the halo is sharp, while the outer edge is more diffused. The sky surrounding the halo also appears darker than the rest of the sky. Refraction effects give rise to colour separation because of the slightly different bending of the different colours composing the light as it passes through the crystals. Reflection are whitish in colour, because the light is not broken up into its component colours, each wavelength being reflected at the same angle. The order of coloration is red on the inside and blue on the outside, opposite to that of the atmospheric corona.

Why is it happening now?

Lunar halos are signs that storms are nearby. There's an old weather saying: 'Ring around the moon means rain soon.' High cirrus clouds - that create the rings of light - often come before a storm.