The claim: Photo shows rare astronomical event called a selenelion
During the two types observed on Earth – solar and lunar eclipses – you don't normally see both celestial bodies simultaneously. But an image circulating on social media claims it's possible for the sun and moon to both appear together during one such eclipse.
"A very rare occurrence, the sun, and the moon are visible at the same time on the horizon. This phenomenon is known as Selenelion when the sun and moon are 180 degrees apart in the sky at the same time," reads a Sept. 20 Facebook post.
A photo accompanying the post purportedly demonstrates this: nestled between two darkened palm trees against a twilight sky, the sun and moon are both visible, with the moon a bit higher in the sky.
The Facebook post and similar ones were shared more than a thousand times in a few days.
While a selenelion is an actual phenomenon – a rare occurrence during a lunar eclipse – it's not depicted in this photo. The original image has been altered.
USA TODAY has reached out to the Facebook poster for comment.
Original photo already altered by photographer
"The moon is real, I just added the sun on the bottom. All (of) the picture beside the sun is real," he told USA TODAY over Facebook Messenger, adding he hadn't intended to recreate an eclipse in any way.
Even if the photo was meant to represent a selenelion, the sun and moon's locations are not in the right place.
During a selenelion (also known as a "horizontal eclipse"), the moon and the sun can be seen at exactly opposite sides of the sky from each other. The sun appears to hover for a few extra minutes before it has actually risen and the moon before it has actually set, Space.com reported in 2014.
The Facebook post actually notes the sun and moon appear 180 degrees apart during a selenelion but fails to note this isn't happening in the picture.
But this is an optical illusion. When light travels through Earth's atmosphere and encounters obstacles, like atmospheric gases or water vapor, it tends to bounce around like a ball in an arcade pinball machine.
This bouncing or bending of light's trajectory, known as refraction, causes any astronomical object to appear to its observers as higher up in the sky than its true geometric location.
And seeing a selenelion is extraordinarily rare.
"It's a phenomenon that's barely possible," Michael Zeiler, who has charted eclipses as the curator of Eclipse-Maps.com, told NBC News in 2014. "Besides being in the right location, you have to have the right conditions. Those right conditions require that you be at a high point, with an excellent view toward the horizon to the east and the west, and have transparent sky conditions to see both the sun and the moon."
Our rating: Altered
Based on our research, we rate ALTERED a photo that is presented as showing a rare astronomical event called a selenelion. The sun in the photo was added digitally by the photographer and was not intended to simulate a lunar eclipse.
Our fact-check sources:
The Conversation, Aug. 8, 2017, How eclipses were regarded as omens in the ancient world
NASA, May 3, 2017, What Is an Eclipse
Inag Blog, accessed Sept. 23, Davide Carovana
searching_for_heaven_, April 30, 2019, Instagram photo
Davide Carovana, Sept. 22, Facebook Messenger exchange with USA TODAY
Space.com, Oct. 5, 2014, Total Lunar Eclipse On Wednesday Will Be a Rare 'Selenelion'
ABC7 Chicago, Oct. 7, 2014, What makes the Oct. 8th lunar eclipse so special? It's an "impossible" occurrence
NBC News, Oct. 7, 2014, Lunar Eclipse Provides an Extra Twist For Skywatchers: Selenelion
Thank you for supporting our journalism. You can subscribe to our print edition, ad-free app or electronic newspaper replica here.
Our fact-check work is supported in part by a grant from Facebook.
This article originally appeared on USA TODAY: Fact check: Altered photo does not show a rare type of lunar eclipse