Astronomical spring arrives, bringing the spectacle of Chicagohenge
CHICAGO - While meteorological spring began on March 1, the start of astronomical spring depends on Earth’s position relative to the sun.
This year, spring officially begins on March 20 at 4:01 a.m., marking the vernal equinox.
The backstory:
Equinoxes occur twice a year, in spring and fall, when Earth's axis is tilted neither toward nor away from the sun. As a result, daylight and darkness are nearly equal worldwide.
During this time, the sun rises directly in the east and sets directly in the west, creating a stunning visual effect in cities with grid-like street layouts.
In Chicago, this phenomenon is known as Chicagohenge, when the sunrise and sunset align perfectly with the city’s east-west streets.
Similar occurrences happen in other cities, such as Manhattanhenge in New York, but Chicago’s version is unique because it happens consistently on the spring and fall equinoxes every year.
For those hoping to catch Chicagohenge, the best viewing opportunities will be from March 20 to March 22 during sunrise and sunset. The event will also be visible on March 21 and 22 if weather conditions permit.
Astronomical Spring Arrives, Bringing the Spectacle of Chicagohenge
Equinoxes occur twice a year, in spring and fall, when Earth's axis is tilted neither toward nor away from the sun. As a result, daylight and darkness are nearly equal worldwide.
What they're saying:
Hunter Miller, a Public Observing Educator at the Adler Planetarium, explains that the equinox is a key astronomical moment when Earth’s axis is in a neutral position.
"That axis is right in that up and down point, where it's shifting between those two tilts, and so if you were right on the equator, that's where you will have that perfectly split daytime and nighttime. Since we're a little off of the equator, it's a few minutes off," said Miller.
As for Chicagohenge, Adler notes that while it has become a popular photo opportunity, it also connects people to the way ancient civilizations used the sun to track time.
"While today it might just be a pretty picture for us, you know, we've got that 'henge' name there, that connection to this ancient history, right? And that's because, you know, dates like this, where the sun is in very predictable positions, were really important for keeping track of the calendar throughout time," said MIller.
What's next:
For the best view of Chicagohenge, find a spot along Chicago’s east-west streets—preferably in a place with an unobstructed view of the horizon.
With clear skies, the sight of the sun perfectly framed between the city’s skyscrapers is a moment worth experiencing.
The Source: Information from this article was provided by Hunter Miller, a Public Observing Educator at the Adler Planetarium, and Chief Meteorologist Emily Wahls.