Chicago Henge 2023: Here’s how it works and how to see it at sunrise and sunset

Twice a year, during the spring and fall equinoxes, the sun rises and sets along Chicago’s east-west street network, creating spectacular photo opportunities as the sun surrounds the Chicago skyline. Spring Equinox is Monday.

Look west just before sunset, says Michelle Nichols, master educator at the Adler Planetarium, The effect is seen about a week before and after the spring equinox. If you miss it, wait another 6 months for the next opportunity. The Autumnal Equinox Day is Saturday, September 23, 2023.

[ Photo gallery: Chicagohenge through the years ]

Throughout the year, the spot on the horizon where the sun rises and sets changes. Go north until the day with the longest daylight hours (summer solstice) and go south until the day with the shortest daylight hours (winter solstice). The cycle repeats every year.

[ Sunrise and sunset times for Chicago ]

The movement of the sun as it appears is caused by the tilt of the earth on its axis, and as the earth moves along its orbit, one of the hemispheres tilts towards the sun and away from it. increase. In the Northern Hemisphere, the North Pole tilts toward the Sun from spring to summer and moves away from the Sun from autumn to winter.

During the vernal and autumnal equinoxes, the Sun illuminates both hemispheres equally, rising and setting directly in the east and west. Chicago’s street grid corresponds almost exactly to the compass points, so the rising and setting suns coincide with the street grid and are framed between the city’s buildings.

The city’s strict east-west grid pattern means that nearly all east-west roads work, but roads that are free of many obstacles are best. Skyscrapers in the Loop offer the best framing opportunities.

According to Adler Planetarium astronomer and Northwestern University professor Shane Larson, the array is named after Stonehenge, a massive stone formation built more than 4,000 years ago. On certain dates, the rising and setting suns align with the stone, leading some scientists to suggest that Stonehenge may have been an observatory or astronomical calendar.

In a gridded city, there may be at least a few days a year when the sun is aligned with the street grid. One of the most famous examples of this phenomenon is New York’s Manhattanhenge. Manhattan’s street grid is offset by about 30 degrees from the compass points, so the date on which the phenomenon is visible does not coincide with the equinox. Astronomer Neil deGrasse Tyson wrote: Manhattanhenge to the American Museum of Natural History.

Source: Michelle Nichols, Master Educator, Adler Planetarium.American Museum of Natural History