A sundog (sometimes written sun dog) is an atmospheric phenomenon that causes bright spots to appear on either side — often both sides, as pictured here — of the sun. The mirage is usually seen when the sun is rising or setting. Sundogs may also have a faint halo that seems to arc around the sun. No matter where in the world the lights are seen, they appear 22 degrees away from the sun.
The meteorological name for a sundog is a parhelion, and they're caused when light passes through ice crystals. The ice is contained in high, thin cirrus clouds or, in colder climates, in lower clouds. It is refracted through the crystals and appears as completely separate light sources. A nocturnal version of the mirage, called moondog, has also been documented.