Monday, January 7, 2013

Sun Pillar

We saw a good sun pillar last night, though my photo didn't come out as well as this one from the web.

A "sun pillar" or "solar pillar" is a vertical shaft of light extending upward from the sun. It appears when the sun is at or below the horizon.

The light in the pillar reflects off the bottom surfaces of ice crystals that are suspended in the air. Those crystals are like tiny hexagonal dinner plates, floating in a horizontal position. Their flat surfaces act like mirrors to reflect the rays of sunlight down to the viewer. (Left: photo by W. A. Bentley)

When such a pillar appears over an artificial light at night, it's called more generally a "light pillar."
Sun pillar (with more photos) from Wikipedia

The best book on this sort of subject is: The Nature of Light and Colour in the Open Air (Dover Books on Earth Sciences)

6 comments:

Gabriel said...

That's really neat. It reminded me of another phenomenon, crepuscular rays.

davidbrasgalla said...

Hey James,
I'm a big fan of these and always enjoy your posts on them... saw a beautiful wintertime pillar two years back, and at midsommar 2011 on Gotland, there was a spectacular one that Kate and I watched for a good 30+ minutes... I took a lot of photos, of course...

Keith Parker said...

I am now wondering if the sun were viewed at a high point in the sky but under otherwise similar circumstances would it project a pillar down?

mdmattin said...

I just saw one of these back on December 23 as I was leaving Stop & Shop, and photographed it before it faded.

Your post inspired me to look it up in Minnaert's Light and Color in the Outdoors. He includes light pillars in a family of halo phenomena and shows their relationships to the terrestrial viewer in this nifty diagram.

Matthew

James Gurney said...

Matthew, thanks for that. Minnaert's book "Light and Color in the Open Air" gives the best explanation of all kinds of atmospheric phenomenon. That book was a big inspiration for my "Color and Light."

Keith, yes, it is possible, but the brightness of the sun tends to drown out pillars if the bright sun is in the same field of view.

Gabriel, that was a great video of crepuscular rays, which are really parallel shafts of illuminated vapor seen in perspective.

David--yes, sounds amazing. Those sightings are unforgettable.

davidbrasgalla said...

James, you inspired me to finally get around to posting on my blog about the night-time light pillars we had here in Stockholm last month. The photos aren't the greatest, but it's quite the interesting phenomena - you might get a kick out it...