What is a Sun Dog?

A sun dog is an atmospheric phenomenon where you can see additional bright patches in the sky on either side of the Sun. Sometimes you just see bright spots, and sometimes you can actually see an arc or even a halo around the Sun. These are all related to sun dogs, and have to do with very specific atmospheric conditions. If you’ve ever seen a sun dog, you were very lucky, and they only occur rarely.

Sun dogs occur because of sunlight refracting through ice crystals in the atmosphere. The crystals cause the sunlight to bend at a minimum angle of 22°. All of the crystals are refracting the Sun’s rays, but we only see the ones which are bent towards our eyes. Because this is the minimum, the light looks more concentrated starting at 22° away from the Sun; about 40 times the size of the Sun in the sky. At this 22° point you can get arcs, a halo, or just bright spots in the sky.

They can occur at any time of the year and from any place on Earth; although, they’re easiest to see when the Sun is lower on the horizon. As the Sun rises, the sun dog can actually drift away from the 22° point. Eventually the Sun gets so high that the sun dog disappears entirely.

There are no set colors with sun dogs. The light from the Sun is being refracted equally by the ice crystals and so we don’t see the colors broken up as we do with a rainbow.

We’ve written several articles about the Sun for Universe Today. Here’s an article about a ring around the Sun, and here’s an article about rings around the Moon.

If you’d like more info on sun dogs, check out this site.

We’ve recorded several episodes of Astronomy Cast about the Sun. Listen here, Episode 30: The Sun, Spots and All.

Fraser Cain

Fraser Cain is the publisher of Universe Today. He's also the co-host of Astronomy Cast with Dr. Pamela Gay. Here's a link to my Mastodon account.

Recent Posts

The Historic Discussion of Ptolemy’s Star Catalog

From the time of its writing in the 2nd century CE, Claudius Ptolemy’s Almagest stood…

2 hours ago

The First Stars May Have Weighed More Than 100,000 Suns

The universe was simply different when it was younger. Recently astronomers have discovered that complex…

3 hours ago

Drag Sail Success! This Satellite Won't Turn Into Space Junk

The European Space Agency successfully tested a solar-sail-type device to speed up the deorbit time…

3 hours ago

Good News! Webb is Fully Operational Again

The James Webb Space Telescope is back to full science operations. One of the telescope’s…

6 hours ago

Soon Every Spacecraft can Navigate the Solar System Autonomously Using Pulsars

If you want to know where you are in space, you’d better bring along a…

16 hours ago

Astronomers Come Closer to Understanding How Mercury Formed

Simulations of the formation of the solar system have been largely successful. They are able…

16 hours ago