What causes the moon to sometimes have a ring around it?

Question

It was a cloudy night and a full moon and there was a full light ring circle emanating around it.

Answer 1

it is optic illusion...

Answer 2

I'll give you the same answer I gave to a similar question:

There are many optical phenomena to be seen in the sky. Probably the most familiar and often the most beautiful is the rainbow. Another phenomenon is the ring around the sun or the moon. This can often be spectacular.

The ring is part of a series of phenomena called "haloes". In polar regions, halo displays can be huge and very complicated. At lower latitudes we don't get quite such spectacular displays.

The most frequently seen of all the halo phenomena is the 22° halo. This is the ring around the moon or the sun. They occur more frequently around the sun than the moon but people, generally, do not look at or near the sun so they don't see the halo. You have to block the sun out first. Around the moon, when it is close to full, the ring is dramatic, taking up much of the sky.

All halo phenomena are caused by the light from the sun or the moon being refracted and reflected through ice crystals. Cirrostratus cloud is a thin sheet of high level cloud composed entirely of ice crystals. When there is cirrostratus cloud, you will see haloes. Often you will not see the cloud, it is so thin, but if there is a halo it is an absolute identifier for the cloud.

Ice crystals come in many shapes but the most common has the faces at 60° to each other. This gives a six sided crystal which also produces the familiar six sided snowflake. The light passing through the crystal is refracted (bent) by the ice and emerges such that we see it as the ring around the moon.

Ice crystals do not always have the same shape and the light can pass through from end to end as well as through the sides. These differences give rise to other halo phenomena such as the 46° halo, tangential arcs, circumzenithal arcs, sun pillars and so on. You are unlikely to see any of these at lower latitudes. There is, however, one other halo phenomenon you can see and I have seen it two or three times myself. These are the parhelia or sundogs. They are bright, often highly coloured spots that appear on the halo on either side of the sun. Once seen, you will never forget them.

Answer 3

you know whats odd. two years ago the day before christmas eve, the moon had a circle around it like a halo, and then two days after that huge sunami that hit asia and africa (the big one i just forgot its name but it was on the news for days) hit. i later found out from a friend that studys weather and astronomy that the halo around the moon means that a sunami or hurricane is about to hit. this is what the ring around the moon means.

Answer 4

caused by atmospheric reflection like think of a contact lense with a light shining down on the curvature, the light bends and illuminates the edges and from your perspective that's what you see.