Tuesday, December 22nd 2020, 6:30 am - Pierre Jules César Janssen spent his career observing solar eclipses. Throughout his career, he made monumental discoveries and inventions.
The name Pierre Jules César Janssen may not come up during daily meals around the dinner table. But Janssen spent his days studying solar eclipses around the world. He invented the Photographic Revolver and escaped a war via hot air balloon.
Pierre Jules César Janssen (22 February 1824 – 23 December 1907). Courtesy of Wikipedia
Though it seems like Janssen did a lot of genius things in his day, today we're going to discuss his solar eclipse expeditions. Namely, his December 22, 1870 expedition from France to Algeria.
On Thursday, December 22, 1870, Janssen left France right before the Battle of Hallue (fought as a part of the Franco-Prussian War from December 23 to 24, 1870) to observe a solar eclipse in Oran, Algeria.
Unfortunately, by the time Janssen made it to Oran, the solar eclipse was completely clouded out. He couldn't see the eclipse, but at least he fled a war.
Janssen has his fair share of successful solar eclipse observations. His expeditions took him to places like Italy, India, Thailand (then Siam), Caroline Islands, and Spain.
It was during his 1868 solar eclipse expedition in India where he noticed bright lines in the spectrum of the chromosphere. This showed that the chromosphere (the second most outer layer of the sun) is gaseous.
During this expedition, Janssen noticed an unknown yellow spectral line in the sun and shared his findings with English astronomer Joseph Norman Lockyer. Lockyer officially recognized it as a new element, and named it helium, from the Greek word helios, meaning sun.
In conclusion, Jules Janssen invented a photograph machine, discovered the gaseous nature of the solar chromosphere, co-discovered-ish helium, escaped a warn-torn environment via balloon, and should be discussed over meals more often.
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