Monday, December 6, 2021

The Winter Solstice




By Mike P. Usher

This is primarily a stargazing column, but we never talk about the somewhat unusual movement of our very own star, the Sun. On December 22, the Sun reaches the Winter Solstice – its most southerly location in the sky. The Sun is now located a few degrees above the spout in the Sagittarius teapot asterism and would be directly overhead at noon on the Tropic of Capricorn. Here on Marco, the Sun crosses the meridian at its lowest point of the year and that likewise, makes this day the shortest of the year.

Unlike points further north, the day on Marco only varies in length by about two hours from longest to shortest although daylight savings time tends to disguise that fact. In cities near the equator, like Singapore, the day only varies in length by a few minutes, while Fairbanks, Alaska will see almost no daylight today.

There are some 48 constellations we have inherited for our Greek and Roman forbearers; over the centuries many constellations were added and some modified to bring the modern total up to 88. As one might expect most of the added constellations are in the deep southern skies never visible from Europe.

Tonight you can view several of these modern constellations; some have odd Latin names like Caelum (the chisel), Horologium (the clock), or Fornax (the furnace) while others have made their way into English like Sculptor and Phoenix. Of the constellations mentioned, most are excessively dim and hard to make out even on the clearest of nights. The Phoenix does have a few decently bright stars, but it is so far south you might need to be on the beach to see it.

There is one extraordinarily bright star in the area, Achernar – although it is so far to the south the horizon murk dims it considerably. In reality, it shines as brightly as Rigel does. Achernar belongs to the heavenly river of Eridanus, but it is a modern addition; in ancient times the constellation ended some six stars further to the north at Acamar. (Achernar can not be seen from Greece nor indeed from most of the United States.)

See you next time!

Mr. Usher is President of the Everglades Astronomical Society which meets every second Tuesday at 7:00PM at the Norris Center, Cambier Park, Naples.

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