September Astronomy

September brings us another astronomical event - the equinox - when days and nights will be approximately equal in length. For those of us in the Northern Hemisphere, this marks the tipping point where the sun will rise later and nightfall arrives sooner.  As things have grown cooler around these parts you don’t have to remind me that autumn is in the air. This is the time of year we stack firewood and roll-out the long sleeve t-shirts and long dungarees.  And the hunting season starts.

Equinox (Latin for equal night) the amount of daylight is nearly equal to the hours of darkness. 

 

Even though the equinox happens at the same moment worldwide the precise time for you depends-upon your time zone. Translation: this equinox comes early in the morning on September 22 at 7:44 AM CDT.  Meanwhile - south of the equator - spring is about to begin.  If you live on the equator the sun will be positioned directly overhead at high noon.

We live just shy of the 45th parallel (equidistant from the equator and pole) and it has been fascinating to observe the transit of the setting sun as it has moved from its furthest advance to the north to now set in the west.  The sun only rises due east and due west on two days of the year - The spring and fall equinoxes. 

 

Today is the astronomical arrival of fall.

 

By comparison, meteorological fall began three weeks ago on September 1.  That may seem to be rushing things a bit; nevertheless, people in the business of measuring and tracking weather statistics will tell you that the coldest three months of the year are December thru February. The warmest three months are typically June thru August.  As a consequence they like the year divided-up into four tidy three month buckets; each beginning with the first of the month.  Hence meteorological fall is September thru November.