Starwatch: The start of fall also brings one of the fastest sunsets of year


Starwatch for the week of September 21, 2020

The autumnal equinox occurs at the same time around the world, here in the Tri-Cities it occurs on September 22nd, at 9:31am. 

This is better known as the first day of fall, when Earth’s axis is facing neither towards or away the sun. On this day, the sun is located directly above the equator, allowing day and night to be nearly equal around the world. 

You can see just that on this GOES satellite imagery from NOAA, where the day/night line is along a common longitude. 

During both the fall and spring equinoxes, the fastest sunsets occur. By sunset time, we are talking the amount of time it takes the body of the sun to sink below the horizon. This is because the sun rises nearly due east and sets due west around the planet, hitting the horizon at the steepest angle.

On the other hand, the slowest sunsets occur at the solstices. 

Weather wise, as the northern hemisphere continues to tilt away from the sun, overall temperatures will continue to cool.

Thanks to EarthSky

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