Two harbingers of autumn — the harvest moon and fall equinox — are occurring within days of each other this week, which will make for some interesting sunsets and moon rises.

The two events can take place up to two weeks apart, but in 2021, the harvest moon rose Monday and will have only lost a nearly indiscernible sliver of fullness by the equinox, set for Wednesday (at 2:21 p.m. CST, to be exact). 

The harvest moon is the name given to the full moon closest to the fall equinox, the day when the sun is exactly above Earth’s equator.

Some phenomena to watch for:

— The sun sets faster around the equinox (be it fall or spring) than at any other time of year, hitting the horizon at the steepest possible angle. 

— The moon rises closer to sunset when a full moon coincides with an equinox. In the coming days, the moon will rise during or near twilight. The presence of dusk-to-dawn moonlight is one reason behind the harvest moon’s name, its glow helping farmers in the field back in the time before tractor headlights.    

— Enjoy the “Chicagohenge” effect. During the fall and spring equinoxes, the sun rises due east and sets due west, which aligns the orb with Chicago’s street grid. Chicagohenge is at its most dazzling downtown, where the setting sun is framed by the city’s architectural canyons, but the spectacle is visible from any of the city’s east-west streets. 

— While you’re looking at the moon, don’t miss Jupiter. That would be the bright “star” hanging out near the moon. With Chicago’s light pollution, Jupiter is nearly the only object visible in the night sky besides the moon — and airplanes — so it’s actually hard to miss. Saturn is in the vicinity, too, but it’s dimmer. 

Contact Patty Wetli: @pattywetli | (773) 509-5623 |  [email protected]