Simma Sky: Autumnal Equinox & The Loneliest Star

They happen twice a year - very close to the time we reset our clocks thanks to Daylight Saving Time. But this isn't about gaining or losing an hour. It's about the seasons of change - more like, changing seasons.

The Autumnal Equinox occurs on September 23rd, 2018 at 9:54 PM EDT. Equinox means "equal night." This is the one day of the year (or two, since there are two equinoxes) that Earth's axis is oriented straight up and down in relation to the sun instead of tilted at 23.5 degrees. That means that sunlight is evenly distributed to all areas of the globe instead of being focused in a certain region as it normally is during any given season.

Sunlight distribution during an equinox as the tilt in the Earth's axis is eliminated for a day. Photo Courtesy: earthsky.org

"Equinox" means "equal night." There are equal parts of daytime and nighttime on the day of the equinox. And because the earth never stops moving around the sun, the "equal parts" of day and night quickly change in their respective directions in the days around the equinox.

I had never heard of it either. Fomalhaut is known as the Autumn Star in the Northern Hemisphere. Autumn is the only time of the year that Fomalhaut is opposite the sun, so it can clearly be seen in the night sky. It's usually the brightest star when you're looking to the south - scientists say there are very few notabe bright stars around it. So how do you see it? Simple - face south on an autumn evening, and it will be the brightest star you see. It's typically less than a third of the way up.

Photo Courtesy: earthsky.org

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