Astrophoto: Double Crepuscular Rays

By Nancy Atkinson - June 10, 2012 at 1:24 PM UTC | Planetary Science
2012-06-10-June-2012.jpg

[/caption]

I'm not sure how often this happens, but I've never seen it before: crepuscular rays on both the west and east horizon at the same time -- or crepuscular and anti-crepuscular rays occurring simultaneously. I'm staying out in the wilds of Minnesota this summer, with great views of both horizons and captured these images last evening, June 9, 2012. The word crepuscular means "relating to twilight," and these rays occur when objects such as mountain peaks or clouds partially shadow the Sun's rays, usually when the Sun is low on the horizon. These rays are visible only when the atmosphere contains enough haze or dust particles so that sunlight in unshadowed areas can be scattered toward the observer.

Then occasionally, light rays scattered by dust and haze sometimes appear on "antisolar" point, (the horizon opposite to the setting sun). These rays, called anti-crepuscular rays, originate at the Sun, cross over the sky to the opposite horizon, and appear to converge toward the antisolar point. Anyone else ever seen this before?

For both crepuscular and anti-crepsucular, the light rays are actually parallel, but appear to converge to the horizon due to "perspective," the same visual effect that makes parallel railroad tracks appear to converge in the distance. One of the astronauts on the International Space Station actually captured crepuscular rays from orbit, showing how the rays are actually parallel. You can see that image and the description

here

.

Below are the two images separately. It was a beautiful evening and a thrilling sight.

[caption id="attachment_95764" align="aligncenter" width="580" caption="Sunset crepuscular rays on the west horizon on June 9, 2012. Credit: Nancy Atkinson"]

[/caption]

[caption id="attachment_95765" align="aligncenter" width="580" caption="Anti-crepuscular rays on the east horizons on June 9, 2012. Credit: Nancy Atkinson."]

[/caption]

Nancy Atkinson

Nancy Atkinson

Nancy Atkinson is a space journalist and author with a passion for telling the stories of people involved in space exploration and astronomy. She is currently retired from daily writing, but worked at Universe Today for 20 years as a writer and editor. She also contributed articles to The Planetary Society, Ad Astra (National Space Society), New Scientist and many other online outlets.

Her 2019 book, "Eight Years to the Moon: The History of the Apollo Missions,” shares the untold stories of engineers and scientists who worked behind the scenes to make the Apollo program so successful, despite the daunting odds against it. Her first book “Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos” (2016) tells the stories of 37 scientists and engineers that work on several current NASA robotic missions to explore the solar system and beyond.

Nancy is also a NASA/JPL Solar System Ambassador, and through this program, she has the opportunity to share her passion of space and astronomy with children and adults through presentations and programs. Nancy's personal website is nancyatkinson.com