In many ways, fall has already arrived. The fall term has started for schools. Football season is underway. And September 1st marks the beginning of the fall weather season. Astronomical fall catches up to them tomorrow. Autumn officially arrives at 7:44 a.m. Central Daylight Time – the moment of the fall equinox.

The change in seasons occurs as the Sun crosses the equator from north to south. The Sun rises due east and sets due west as seen from the entire planet. And the length of day and night are about equal.

That balance won’t last long. In the northern hemisphere, the days will grow shorter and the nights longer until we reach the winter solstice, in December. As that happens, the sunrise and sunset points will slide southward.

As the season changes, so do the stars. At nightfall, Arcturus, the brightest star of summer nights, is dropping lower in the west. The signature star pattern of the season, the Summer Triangle, is moving to the western side of the sky. And the scorpion is getting ready to disappear in the southwest.

In the meantime, the Great Square of Pegasus is in the east at nightfall, ready to climb high across the sky during the night. Constellations associated with the flying horse are moving into view as well. And so are the constellations of the Celestial Sea – water-related constellations like the fish, the sea goat, and the water boy – stellar sights for the longer nights of autumn.

Script by Damond Benningfield