The fall equinox technically occurred at 8:30 a.m. Tuesday in Chicago, though you’d be forgiven for not having noticed. Leaves didn’t immediately change color, the temperature didn’t plummet, and the air didn’t take on the aroma of pumpkin spice.
But the seasonal shift — which marks one of two moments in the year when the sun is exactly above the equator — will make itself spectacularly apparent at sunset.
That’s when the unmistakable and highly anticipated “Chicagohenge” occurs. During the fall and spring equinoxes, the sun rises due east and sets due west, creating an effect dubbed Chicagohenge (in reference to Stonehenge), when the sunset is strikingly framed by the city’s skyscrapers.
Biked over to Wacker Drive to try a less crowded spot for #Chicagohenge. Interesting angle, but the wildfire smoke really choked out the intense, golden light that typically spills down the 'concrete canyons' of the city // #ILwx pic.twitter.com/PB4oJ4RdIF
— Nick Ulivieri (@ChiPhotoGuy) September 22, 2020
Photography buffs scramble to capture Chicagohenge at its most dazzling, centered in downtown’s architectural canyons. But the phenomenon is visible from any of the city’s east-west streets, said Michelle Nichols, director of public observing at the Adler Planetarium.
On wider streets, the effect will linger for a couple of days, she added.
This year’s equinox sunset will be a deeper shade of orange than normal, due to lingering smoke in the upper atmosphere, which has wafted into the area from the West Coast wildfires.
Under normal conditions, Earth’s atmosphere scatters the sun’s blue light. Particles from the wildfires are heightening that filtering of blue light, making the sun’s red light even more prominent, Nichols explained.
As long as folks are already outside enjoying the equinox sunset, they might as well stick around for another celestial show: The International Space Station will be visible in the early evening sky for the next few days, Nichols said.
It’s bright enough to be seen with the naked eye, said Nichols, who advised against trying to use a telescope, largely because the space station moves too quickly to catch with a fixed lens.
“It will look like an unblinking airplane,” she said.
For more information on how best to see the space station, visit NASA’s “Spot the Station” website.
— Craig Shimala (@cshimala) September 22, 2020
— Don Fardo (@fardmuhammad) September 22, 2020
The official start of Fall - the Fall/Autumnal Equinox - is THIS MORNING, at 9:30 AM EDT. This marks the time when the day-to-night line, called the terminator, is perfectly vertical from pole to pole and the sun is directly over the equator. #FallEquinox #FirstDayOfFall pic.twitter.com/kkSH3HM0RN
— National Weather Service (@NWS) September 22, 2020