While there’s no formal definition of a Supermoon, it’s typically considered a full moon that occurs at perigee.
Perigee is the point in the moon’s orbit in which the moon is closest to the earth.
A full moon at perigee will look up to 14 percent bigger and 30 percent brighter than a full moon that is located farthest from the earth, known as apogee.
Sunday night, we got something more than just a super moon!
Look at this — it is a super rare moondog!
— Drew Richards (@drew_richards) December 4, 2017
Similar in formation to a sundog, moondogs only happen during evenings with quarter-to-full moons, and thin cirrus clouds that contain ice crystals must be in place in order to refract the moonlight and produce the “second moon” that you see to the left and right of the actual moon.
Is that a moon halo?
The moondogs form along a 22 degree halo as the moonlight refracts through the ice crystals in the cirrus clouds, very similar to when sun halos form in the daytime.
Earthsky.org explains it very simply: “Halos are a sign of high thin cirrus clouds drifting 20,000 feet or more above our heads.”
“These clouds contain millions of tiny ice crystals. The halos you see are caused by both refraction, or splitting of light, and also by reflection, or glints of light from these ice crystals.”
It is called a 22-degree halo because the ring has a radius of approximately 22 degrees around the sun or moon.
According to the site Atmospheric Optics, the halo remains the same diameter no matter what position the sun is found in the sky.
At times, portions of the circle may be missing, so only a segment can be seen.
— Carley S Windsor (@Windsor_Carley) December 4, 2017
Did you see a “supermoon halo/moondog” Sunday night? If so, share your photos with us using the button below!