A strange yellow hollow in the sky

If you looked up and saw the Moon wrapped in a yellow hollow you were not imagining things. It really was there. It looked like the Moon had decided to wear a glowing scarf. A fashionable choice for the season.

This ring of light is called a halo. It appears when the Moon shines through thin clouds that contain tiny ice crystals. These crystals act like miniature prisms. They bend the moonlight and create a soft circle of light around it. It is nature’s way of showing off without asking for applause.

Why it happens in autumn and winter

Autumn and winter are the perfect seasons for this trick. The air is colder. The clouds are thinner and higher. They contain more ice crystals. These are the ideal ingredients for a halo.

In summer the clouds are usually thicker and warmer. They contain water droplets instead of ice. Water droplets are good for rain but terrible for halos. So the Moon saves its best performances for the colder months.

The colour that surprises everyone

Many people expect a halo to be white. Yet sometimes it turns yellow. This happens when the ice crystals scatter the light in a way that removes some of the blue tones. What remains is a warm yellow glow. It looks cosy. Almost like the Moon is trying to match the colour of autumn leaves.

The yellow tone can also appear stronger when the Moon is low in the sky. The light travels through more of the atmosphere. The atmosphere filters out even more blue. The result is a golden ring that looks almost magical.

A moment worth stepping outside for

Luxembourg is not famous for dramatic skies. It is famous for fog and drizzle. So when the Moon decides to put on a show it is worth stepping outside. Even if it is cold. Even if you have to put on that winter coat you pretend you do not need yet.

A halo around the Moon is a quiet spectacle. It does not flash. It does not roar. It simply glows. And for a moment the night feels a little more special.