The sun appeared blue in 1831 - and the reason behind it has finally been revealed

Back in August 1831, scientists of the time were left baffled after the sun appeared to turn blue and now experts think they know why it happened.

Nearly 200 years ago, a two-year-long period of cold weather across the globe was ushered in when the sun turned blue. During the short, sharp cooling event, average temperatures dropped by around 1°C.

Reports from around the world, including China, Europe, the US and the Caribbean, in August 1831 described the sun as appearing “blue, purple, and green”.

Experts theorised that the sun’s strange appearance occurred due to the release of volcanic dust and gases that scattered the light in a strange way.

For years, the location of the eruption has not been pinpointed, but experts now finally think it came from the Zavaritskii caldera, solving the 200-year-old mystery.

Scientists from the University of St Andrews in Scotland gathered evidence that the eruption emerged on the uninhabited remote island of Simushir, and their results have since been published in a study.

Simushir is located in the Sea of Okhotsk and forms part of the Kuril Islands in the Russian Far East, fairly close to Japan.

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A geochemical analysis of ice-core samples revealed a “perfect fingerprint match” of old ash deposits.

Dr Will Hutchison, the lead study author from the School of Earth and Environmental Science at the University of St Andrews explained: “We analysed the chemistry of the ice at a very high temporal resolution. This allowed us to pinpoint the precise timing of the eruption to spring-summer 1831, confirm that it was highly explosive, and then extract the tiny shards of ash.

“Finding the match took a long time and required extensive collaboration with colleagues from Japan and Russia, who sent us samples collected from these remote volcanoes decades ago.”

“The moment in the lab when we analysed the two ashes together, one from the volcano and one from the ice core, was a genuine eureka moment. I couldn’t believe the numbers were identical. After this, I spent a lot of time delving into the age and size of the eruption in Kuril records to truly convince myself that the match was real,” he added.

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