This is one of those images that should go straight to NASA’s Astronomy Picture Of the Day (APOD) not just because he’s got the best first name out there but because science!
Ok, let’s jump right into this image and unpack what we’re looking at piece by piece. The image was taken by Daniel in Bondurant Iowa after he had gotten up early for a chance at some sub-zero lunar halos and needless to say, he wasn’t disappointed. For your best chances to see events like this, catch the Sun or Moon while it’s low on the horizon, say, 30 degrees and the colder the better though this isn’t always necessary. Solar events are more frequent because the Moon is only full once a month (typically) while the Sun is always full. The Moon doesn’t need to be completely full but close to it.
For starters, that beautiful light ring around the Moon is what’s called a lunar halo, or more specifically a 22 degree lunar halo. There are 22 degree halos and around them you will sometimes be treated to another, even larger ring around the 22 degree halo called a 46 degree lunar halo (not in this image). Most lunar halos are colorless due to the Moon being less bright than the Sun whereas solar halos often resemble rainbows in color.
The two bright points of light at roughly 9 and 3 o’clock are what’s known as moon dogs, mock moons or paraselene while their solar counterparts would be called sun dogs, mock suns or parhelion (not perihelion, but close). Because of their bright nature they tend to be either bright white or rainbow colored.
At the 12 o’clock position of the halo is another region of light which appears to be the bottom of what’s called an upper tangent. But what about that slow arc of light emanating from the 9 o’clock position? It’s called a 120 degree perihelic circle and these are a real treat if you ever get the opportunity to witness one because they encircle the entre sky (though you may only see a fragment) at the same elevation that the Sun or Moon is at and they are typically white.
All of these fascinating halo phenomenon are caused by ice crystals in the atmosphere aligned just right to where the light from the Sun or Moon in this case is reflected and refracted to the ground below in some pretty amazing geometry.
We’re not done with this image yet! If you have a look along the ground what do you see? Some of you may have seen or heard of these before. They’re called light pillars and like the lunar halos, these are created by light interacting with ice crystals in the air. These particular light pillars are coming from town lights on the horizon interacting with snow being blown around and kicked up in the air.
You can’t really pack much more awesome into one image so congrats to Daniel on a fascinating capture and I hope you all enjoy this amazing pic!
22 Degree Lunar Halos: http://www.atoptics.co.uk/halo/circmoon.htm
46 Degree Halos: http://www.atoptics.co.uk/halo/46hal.htm
Parhelic Circles: http://www.atoptics.co.uk/halo/pcpaths.htm
120 Degree Parhelia: http://www.atoptics.co.uk/halo/120pars.htm
TimeAndDate Atmospheric Phenomenon: https://www.timeanddate.com/astronomy/optical-phenomenon.html