Winter Solstice: The Shortest Day

The solstice will occur Thursday, Dec. 22, 2011. On this day, the sun is at its farthest southern declination, and is 6.5 degrees away from the center of the Milky Way.

CREDIT: Starry Night Software

This week, the sun will reach that point where it will appear to shine farthest to the south of the equator, marking the moment of the winter solstice, the shortest day of 2011 in the Northern Hemisphere.

The winter solstice occurs Thursday at 12:30 a.m. EST (0530 GMT), which corresponds to 9:30 p.m. PST on Wednesday for observers further west. At the time, the sun will be passing over the over the Tropic of Capricorn.

Here's how northern winter solstice works: Since June 20, the altitude of the midday sun has been lowering as its direct rays have been gradually migrating to the south.

The sun's altitude above the horizon at noontime is 47 degrees lower now, compared to six months ago.

As we often mention, your clenched fist held at arm's length measures roughly 10 degrees, so the sun at midday is now nearly "five fists" lower in the southern sky compared to June 21.