APOD: Pillar at Sunset (2010 Mar 06)

[APOD Robot]

Pillar at Sunset

Explanation: Reddened light from the setting Sun illuminates the cloud banks hugging this snowy, rugged terrain. Inspiring a moment of quiet contemplation, the sunset scene included a remarkable pillar of light that seemed to connect the clouds in the sky with the mountains below. Known as a Sun pillar, the luminous column was produced by sunlight reflecting from flat, six-sided ice crystals formed high in the cold atmosphere and fluttering toward the ground. Last Monday, astronomers watched this Sun pillar slowly fade, as the twilight deepened and clearing, dark skies came to Mt. Jelm and the Wyoming Infrared Observatory.

<< Previous APOD

Discuss Any APOD

Next APOD >>

[/b]

[neufer]

Pillar at Sunset

Are you sure this isn't Pecos Bill's Slue-foot Sue taking off?
http://www.youtube.com/watch?v=uhPnnnDwA3M

[logmark]

The appearance of a "column" doesn't warrant a notation that a column actually exists. No differently than an apparent "column" of light seems to rise vertically from a cold winter night lamp post, this light pattern is created in horizontal space over some distances.

In this case, with the sun very low, the ice-laden layer must have been relatively low to the ground to be reflecting or refracting the sun's rays over the horizontal distances necessary to form the apparent "column" - thus the rarity even in areas of common cold and sun. Still air over large areas/distances, very cold temperatures, an oriented ice crystal laden stratus, and a point light source and - poof - an arc of reflecting or refracted light between the source and the observer
which appears to the eye (or camera) as a column. No column. None.

Just chemistry, physics and geometry. Ah-h-h - and the beauty of it...