Utah Skies: Fall Equinox And Harvest Moon

Sep 28, 2021

Sunset locations against Wellsville mountains Sept 22 and Summer solstice June 21.
Credit Tom Westre

Have you noticed the weather is changing? The days and nights seem cooler as the month of September moves on.



 

 

The seasons are transitioning this month. Summer is coming to an end and fall officially begins on Wednesday September 22 at 1:21 pm in the Northern Hemisphere. This is called the autumn equinox. On this date the sun rises due east and sets due west. The day and night are about equal. From now on for the next three months the sun rises earlier and sets earlier as the sun sets farther south each day. The days will be shorter and the nights longer.

All of this is due to the 23 ½ degree tilt of the earth’s axis. During the autumn equinox the earth's axis tilts away from the sun causing the sun to appear lower in the sky. At the spring equinox, the earth’s axis tilts toward the sun and the sun appears higher in the sky.

The word “equinox” comes from the Latin meaning “equal” and nox meaning ”night,” therefore equal day and night.

Around the time of the fall equinox the full moon appears. This year the full moon took place yesterday on Monday September 20. The full moon that occurs around the time of the autumn equinox is called the harvest moon.

Traditionally the harvest moon’s light helped farmers work late at night during harvest season

While you’re enjoying the harvest moon look for the planet Venus in the west and Jupiter and Saturn in the southeast after sunset.