EarthSky | Oddly formed suns and moons close to the horizon


View at EarthSky Community Photos. | Ron Mauer in Hilton Head Island, South Carolina, captured this moonrise on November 19, 2021, the night after the partial lunar eclipse. He wrote: “The atmospheric distortion was crazy during this evening’s moonrise over the Atlantic Ocean. This image is my favorite from a number of shots, each more distorted than the next.” Keep studying to be taught what causes oddly formed suns and moons close to the horizon. Thank you, Ron!

Great picture alternatives

Sunrises, sunsets, moonrises and moonsets are wonderful alternatives to seize that significantly lovely {photograph}. When you see them close to the horizon, the sun and the moon can look distorted in essentially the most fascinating methods. Their edges might seem jagged. Their backside areas might flatten out or shrink right into a pedestal. Nearby clouds and twilight shade assist make the inventive view even higher.

But why does it occur? What causes the distortion within the look of a low sun or moon?

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The reply is atmospheric refraction, the impact of sunshine touring by totally different densities and temperatures of air. Refraction is identical impact that causes a spoon in a glass of water to look damaged in two.

The truth is, if you gaze towards any horizon, you’re wanting by extra air than if you gaze overhead. It’s this higher amount of air that causes oddly formed suns and moons. At zenith (straight up) the environment shall be at its thinnest. That’s why skilled astronomers desire to look at their objects of curiosity as excessive up on the sky as potential (and as their telescopes enable), to decrease the results of any atmospheric distortion decrease within the sky.

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Diagram with shorter vertical red line and longer horizontal red line between circles representing surface to top of atmosphere.
The pink strains present that, regardless of the place you’re on Earth, as you look towards a horizon, you’re wanting by extra environment than if you look overhead. Image through Phil Plait.

More environment = extra distortion

Once you possibly can settle for there’s extra air within the course of a horizon, you possibly can take into consideration all of the alternative ways refraction impacts a dawn, sundown, moonrise or moonset.

Plus … it’s not solely the quantity of environment that performs a task. It’s additionally the stress, the temperature and the humidity, all of which have an effect on the air density and thereby additionally the quantity that mild rays shall be bent, or refracted, alongside their path.

Thus, temperatures various with totally different layers of air could cause the sunshine to unfold to present a layered picture of the thing you’re . In different phrases: the sunshine is refracted extra in some layers than in others.

Diagram of lines pointing from viewer to horizon at two circles, the upper flattened.
Les Cowley at Atmospheric Optics explains why a spherical object seems flattened close to the horizon: “Rays from the setting sun (lower) are refracted by the atmosphere and make it appear higher in the sky [higher image]. The lower limb is lifted more than the top limb, making its image oval.” Image through Les Cowley.
Ocean sunset with lower rim of sun spread out while upper part remains a round disk.
View at EarthSky Community Photos. | Marlin Bloethe Marlin caught this “omega sunset” on January 12, 2021 at Fishers Island, New York, wanting westward over Long Island. This type of mirage – referred to as omega because of its resemblance to the Greek letter – happens because of a change in temperature, a temperature gradient, within the vertical course above the horizon.

More distortion = oddly formed suns and moons

The bending of sunshine rays on this method is known as atmospheric refraction. Without any type of disturbance, mild would journey in a fully straight line, and provides your eye a real picture of what you see (so long as your eye isn’t additionally disturbing it, however that’s one other story).

For objects with a small angular dimension like stars, atmospheric refraction causes them to twinkle extra the nearer to the horizon they’re.

And for an object with a good quantity of floor space just like the moon and the sun, there’s a change within the refractive impact alongside the peak of it: the higher half travels by much less environment than the decrease half, which makes the decrease half extra distorted.

Flattened semicircle of sun bright yellow on top similar to a sunny-side-up egg.
Helio de Carvalho Vital captured this UFO-ish spread-out sun on January 1, 2015. See this image and more here.

What is a inexperienced flash?

When atmospheric refraction is at its most excessive, you may see a mirage. It’s the very same scenario: the sunshine is bent and distorts the picture. But right here it may be refracted a lot that there’s a mirroring impact and you will note drawn out or a number of photographs, or displaced photographs – the moon might seem greater on the sky than it truly is.

A widely known mirage for the sun is the sought-after green flash.

Sliver of sun visible above ocean horizon with glowing green smudges above it.
A green flash simply earlier than the setting of the sun, one other instance of a mirage. Photo through Chris Mannerino.

Why sunsets are pink

Additionally, mild of various wavelengths is affected otherwise. For instance, blue mild (which has extra vitality/shorter wavelength/greater frequency – all of those are the identical factor however with a distinct title) is extra affected by refraction than pink. That means pink colours have a bigger likelihood of coming by to you than blue, which is why sunsets and sunrises seem extra pink and the moon is redder close to the horizon.

The results of refraction is nature’s personal type of artwork, maybe harking back to impressionism. Maybe that’s the reason we discover it so interesting. The video under, captured by Mike Cohea, superbly exhibits the impact of the thicker environment because the young moon sets over Newport.

So, exit, deliver your digital camera and preserve watching the horizon (however by no means stare immediately, or by a digital camera, on the sun). Then ship your finest outcomes to EarthSky Community Photos, in order that we are able to add them to this story!

More images of oddly formed suns and moons

Orange orb against dark sky with a sliver of reflection below it.
View at EarthSky Community Photos | Greg Diesel-Walck in Ormond by the Sea, Florida, captured this picture on December 1, 2020. The atmospheric refraction offers the seemingly melting moon a mirrored image – a mirage.
Moon rising over water under a bridge, sitting on a 'pedestal' of light.
View at EarthSky Community Photos. | Chris Mannerino captured this omega moonrise on November 28, 2020, in San Diego, California.
Orange sun against dark sky looking like a mushroom cloud.
Gene Aubin in Newport, Oregon, caught the setting moon over the ocean on the morning of October 5, 2017. The layered impact inflicting a jellyfish-like distortion is a sort of mirage, attributable to refraction. Visit Gene at GuruShots.
Silhouette of woman holding hands with two children against enormous yellow moon near horizon.
“This is my wife and my two kids watching tonight’s full moon rise above the horizon … The moon is somewhat deformed in the lower half due to atmospheric refraction.” Photo by Göran Strand.

Bottom line: The quantity of environment between your eye and what you observe determines how a lot the picture you see shall be distorted. This phenomenon – atmospheric refraction – is the rationale why the moon might seem flattened close to the horizon.

Read more on atmospheric refraction and mirages, with images and explanations, at Les Cowley’s website Atmospheric Optics.

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