Stunning 'Phoenixhenge' sunset marks fall equinox

KPNX Breaking News 1

PHOENIX - A driver’s nightmare and a photographer’s dream, Phoenixhenge has returned.

Each year on the vernal and autumnal equinoxes, the sun rises and sets perfectly along Phoenix’s east-west streets.

In a city not exactly known for its magnificent fall colors, Phoenixhenge is a signal of the changing seasons -- and it’s all thanks to our perfectly gridded layout.

“This is an anthropological phenomenon. It happens because of human interaction with our environment,” according to David Gamez, a planetarium program specialist at the Arizona Science Center.

Here’s a quick explanation of why Phoenixhenge happens:

Normally, we’re not looking at the sun straight on because the earth is tilted on its axis, so Earth’s northern and southern hemispheres usually trade off on which receives sunlight most directly as Earth orbits the sun, according to Gamez. This axial tilt is responsible for seasonal changes throughout the course of the year.

Gamez said the equinox occurs on two days of the year when the celestial equator of the earth is looking straight at the ecliptic plane of the sun. Therefore, the northern and southern hemisphere share the same amount of sunlight for about one day.

In Phoenix, streets run north, south east and west. So on a day like Sept. 22, when we’re looking straight at the sun, the sun will appear to align perfectly with those streets as it rises in the east and sets in the west.

Mike Marron, the president of the Phoenix Astronomical Society, said drivers may experience some difficulty during Phoenixhenge.

“It’s trouble for the commuters at morning and at night because they’re looking directly at the sun,” he said.

Marron suggests all the usual precautions to avoid looking at the sun: Use sunglasses and visors, and try to avoid driving at dawn or dusk if you can.

“I realize [the sun] does get dimmer as it gets closer to the horizon because it’s passing through so much atmosphere,” he said. “But those afterimages that you see are telling you that your eye is damaged, just slightly.”

Phoenix isn’t the only city that gets a “henge” twice a year. Across the country, other cities with grid layouts get a similar event.

Like “Manhattanhenge,” Manhattan’s version of the event, Phoenixhenge is also a social media sensation -- when photos of a swollen orange sun flood social feeds.

The sun looks like that because of its proximity to the horizon.

Marron said objects in the foreground will make the object in the background look bigger, explaining why the sun looks so massive during Phoenixhenge.

As for the orange/reddish color of the sun, Marron said sunlight is passing through more atmosphere during the equinox, meaning the rays of the sun are getting refracted slightly more.

Now that you know all about Phoenixhenge, it’s time to go out and enjoy it. The sun will rise at 6:16 a.m. and will set at 6:26 p.m. in Phoenix on Friday, according to the National Oceanic and Atmospheric Administration.

You can share your Phoenixhenge photos by sharing them on social media with #BeOn12 or by emailing them to pictures@12news.com.

Live video courtesy City of Phoenix, Phoenix.gov/CityCam

© 2017 KPNX-TV


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