A natural phenomenon, the setting sun casts a green light as it dips below the horizon. (Picture: Getty)
The sun appeared green – well, momentarily.
Across the horizon, a sudden green flash appeared in the sky in Oregon as the sun set over the ocean.
The moment was captured by Craig Hayslip, a faculty research assistant at Oregon State University, on April 20, just 15 miles west of Coos Bay.
On Instagram, he wrote: ‘Tonight’s sunset west of Bandon, Oregon, and then a green flash behind a cloud at the end.’
What is the green flash?
The green flash is another example of an optical phenomenon that sometimes occurs around the moment of sunset or sunrise. It lasts for no longer than two seconds.
The flash occurs when the Earth’s atmosphere causes light from the Sun to separate, or refract. As the sun’s light, which appears pure white, passes through a prism, the light refracts and creates a stunning flash that is visible to the human eye.
However, the flashes only happen at certain temperatures when air at high altitude becomes warmer, meaning the flash is more likely to be spotted over water than on land.
The green colour is produced by the atmospheric refraction of light, which causes objects near the horizon to appear slightly higher in the sky than they actually are.
Refraction is stronger for blue and green light than it is for yellow and red light, which leads to a bluish or greenish hue on the upper side of the sun.
How can you spot the green flash?
The flash lasts for around two seconds and is extremely rare to see. Space.com’s skywatching columnist, Joe Rao, said he has been ‘an avid skywatcher for over half a century’ – but despite looking for the green aura on many different occasions, he has definitively spotted it just twice.
For those hoping to catch a glimpse of green flash, a few tips and tricks can help. Generally speaking, the flash appears more on the coast than on land, so getting to a low horizon level will increase your chances.
Cooler weather and the absence of red tints in the sky will help, with reports citing that when the horizon seemed to have a bright white or yellowish glow.
It should be noted that you should avoid the sun’s gaze until the last moment to minimise your risk of eye damage.