Sometimes you look up on a clear day or night and see a huge circle of light around the sun or moon. This ring or circle is called a halo by scientists. We get many messages throughout each year from people who’ve just spotted a ring around the sun or moon. Solar and lunar haloes are pretty common, but they’re so mysterious-looking that people often express amazement upon seeing them. Yesterday – May 16, 2012 – EarthSky’s Facebook page received a rash of photos of a beautiful sun halo seen in Washington state.
Sun halo seen in Washington state on May 16, 2012. Image via EarthSky Facebook friend Sean Abbasi
Notice in the photos that the sky looks fairly clear. After all, you can see the sun. And yet halos are a sign of high thin cirrus clouds drifting 20,000 feet or more above our heads.
Sun halo on May 16, 2012 via EarthSky Facebook friend Nonya Justagirl
These clouds contain millions of tiny ice crystals. The halos you see are glints of light from these ice crystals, which have to be oriented and positioned just so with respect to your eye, in order for the halo to appear.
Sun halo seen in Washington state on May 16, 2012. Image via EarthSky Facebook friend Jana Kitty Daze.
That’s why, like rainbows, halos around the sun – or moon – are personal. Everyone sees their own particular halo, made by their own particular ice crystals, which are different from the ice crystals making the halo of the person standing next to you.
Lunar halo via master sky photographer Dan Bush.
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. If you do see a halo around the moon or sun, notice that the inner edge is sharp, while the outer edge is more diffuse. Also, notice that the sky surrounding the halo is darker than the rest of the sky.
By the way, there’s an old weather saying: “ring around the moon means rain soon.” There’s truth to this saying, because high cirrus clouds often come before a storm.
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In all seriousness, I have noticed white commercial airplanes what appears to be “making clouds” and the halos look different. They are more pastel or grim in color not vibrant like normal. Do you know what these planes are spraying? I’ve seen them fill a clear sky with these “clouds”.
the govt. has a seeding program? to make clouds, rain? they spent a lot of money last year to help Texas and their no rain situation. even did it out in the pacific ocean to start things. nothing happened. beautiful graph on cloud radar. ha.
Halo is a name for one circle. what is it called when there are two Halo’s around the moon. can there be three, even? have seen this with a harvest moon even in southeast Kansas.
Nice article and great photos!
Oh, yes, I remember my late grandmother predicting rain using halos and I just couldn’t understand how could she tell that it were about to rain when it was such a nice day and how was she that accurate every time. When the time came I learned both about the ancient wisdom of peasants and the scientific explanation, but magic is not lost yet!
By the way, halo comes from an ancient greek word for ‘threshing floor’, that still survives in modern greek as ‘aloni’. Just type this word and search the web for images, and you will get an idea of how an ‘aloni’ used to look like during mid-twentieth century when they were finally abandoned, and why it came to be a scientific term for the phenomenon.