Do You See A Sun Dog or Sun Halo?
Is there a little piece of rainbow hanging in the sky next to the Sun? How about a strange circle of light around it? You may be seeing a Sun dog (sundog) or Sun halo. Learn what causes these sunny sensations and what they may say about the weather coming your way!
What Is A Sun Dog (Sundog)?
Sun dogs, also known as mock Suns or false Suns, are dimmer, fuzzier copies of the Sun that appear to the left and right. They form when sunlight bends through hexagonal ice crystals high in the sky, especially when cirrus clouds are present. Sun dogs often display the colors of the rainbow (with reds facing toward the Sun and blues away from it).
Depending on the sky conditions, you may only see one or two Sun dogs approximately 22 degrees (about the distance of two fists) away from the Sun. When there are more ice crystals in the atmosphere, Sun dogs can extend all the way around to create a full circle—a Sun halo.
Sun dogs and sun halos may occur at any time of the year, but are almost always noticeable when the Sun is lower in the sky—about an hour or two before the Sun rises or an hour or two after sunrise. If wispy clouds are in the sky, their colors are more pronounced.
The most common Sun halo is a circle with a 22-degree radius around the Sun that is often brighter on the top and bottom. (If you block the Sun with your thumb, your pinky should touch the edge of the halo. Note: Do not look directly into the Sun.)
Related: Moon Halo And Night Rainbow (Moonbow) Explained
Sun Halo Weather Lore
Sailors who saw a halo or ring around the Sun or Moon often believed that unsettled weather was 18-24 hours away.
Sun Pillars
On rare occasions, you may see a narrow, vertical shaft of light extending straight up from the Sun at sunrise or sunset. This is a Sun pillar.
Sun pillars develop when ice crystals slowly fall through the air. Air resistance causes these crystals to lie nearly flat as they flutter to the ground.
Unlike halos, the crystals do not refract or bend light. Instead they reflect the rays of the Sun. When the crystals align they create a pillar effect.
Sun pillars usually appear 5-10 degrees high—sometimes even higher. (Your clenched fist held at arm’s length measures roughly 10 degrees). Pillars can sometimes appear even longer and brightest in the moments just before sunrise or just after sunset.
They may take on the colors of the Sun and clouds or appear white. Other times they are shades of yellow, red, or (infrequently) purple.
On rare occasions, the same phenomenon occurs with rising or setting of the Moon, though it is not as bright.
Join The Discussion
Have you ever seen a Sun halo or Sun dog?
Share your photos of sunny sightings!
Have any questions? Let us know in the comments section below.
Dean Regas
Dean Regas is an expert astronomer and a renowned author who has written six books, including 100 Things to See in the Night Sky and How to Teach Grown-Ups About Pluto. An astronomer with more than two decades of experience, Dean is a dynamic writer and public speaker who brings the complicated field of astronomy down to Earth for students of all ages. From 2010-2019, he was the co-host of the PBS program Star Gazers. He is a frequent guest on National Public Radio’s Science Friday with Ira Flatow and NPR's Here & Now. He also hosts a popular astronomy podcast called Looking Up with Dean Regas. Learn more about him at www.astrodean.com
Joe Rao
Joe Rao is an esteemed astronomer who writes for Space.com, Sky & Telescope, and Natural History Magazine. Mr. Rao is a regular contributor to the Farmers' Almanac and serves as an associate lecturer for the Hayden Planetarium in New York City.
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Joe Rao#molongui-disabled-link
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Joe Rao#molongui-disabled-link
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Joe Rao#molongui-disabled-link
seen my first sun-dog and it was beautiful i am 76 and always outside and my first citing-i would put a picture here but don’t know how