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Birthday · November 9, 2006

Halo and Hexagons

November 9, 2006

When you were born, the Sun rose on a world that had never seen you before. Since then, every dawn has arrived in a universe subtly altered...

Halo and Hexagons

A little universe, just for you

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APOD published November 9, 2006. Credit: Gil Esquerdo (Whipple Observatory). A publication-date match, not a photo taken on your date. Independent of NASA.

Behind the image

Halo and Hexagons

Original APOD · November 9, 2006

As a bright November Moon lit up the night sky last week, Gil Esquerdo spotted this lovely Moon halo overhead at the Whipple Observatory on Mt. Hopkins, Arizona. In the foreground, the structure and individual component mirrors of Whipple's 10 meter gamma-ray telescope actually block direct light from the lunar disk, emphasizing the halo in this dramatic view. The halo was caused by ice crystals in the thin high clouds above the observatory - crystals that are hexagonal in shape and produce the characteristic ring of light with a 22 degree radius. In fact, the ice crystal shapes are much like the flat, hexagonal mirrors of the specialized telescope in the picture. Used together the mirrors can collect brief flashes of optical light caused by high-energy gamma-rays impacting Earth's atmosphere.

Image credit: Gil Esquerdo (Whipple Observatory)

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